Lead and zinc mining in northeastern Oklahoma began in 1891 near Peoria.

Several other communities in the area were settled as a result of these mining activities, increasing the area population to approximately 32,000 people in the early 1920s.

Estimates state that as many as 250,000 people were directly or indirectly affected by portions of the Tri-State (Kansas, Oklahoma, and Missouri) Mining District activities.

At one time the Picher Mining Field was the leading U.S. producer of lead and zinc, supplying approximately 26.3 percent of the nation’s lead and zinc products.

From 1907 through 1946 more than 1,900,000 tons of lead and zinc were mined in the area, at a value of more than $202 million.

To reach the underground bodies of ore throughout the Tri-State Mining District, early miners and mining companies excavated hundreds of working and prospective mine shafts.

Thousands of drill holes dotted the mining area.

During the early mining era there were more than 200 processing mills operating in the Picher Mining Field.

Each mining company had a mill located at its most productive site.

An aerial view of the Picher Field taken in 1995 that illustrates the high concentration of mining activity.

Water was pumped from underground through the mill and used to separate the ore from the waste rock.

The mills had the capacity to pump between 2,000 to 10,000 cubic feet of water per minute to separate between 30 and 70 tons of ore per hour.

A mining method known as jigging and tabling was used to extract the ore, but it was not very efficient.

Beginning in the 1920s the use of the flotation process ensured the recovery of 80-85 percent of the metal contained in the crude ore.

Between 1920 and 1945, 36 million gallons of water were pumped daily from the mines by 63 major pumping stations in order to keep the mines dry.

In 1934 the Eagle-Picher Mining Company began construction on the Central Mill;

the mill was completed in 1935 with a capacity of 500 tons of ore per hour.

It was believed that this mill would replace all of the other mill sites;

an assumption that did not prove true.

In 1947 there were 65 mining companies operating 135 mines and 46 mills in the Tri-State Mining District.

Even with the Central Mill's increased capacity, it was not possible to handle production for all the mines.

The mills produced more than three billion tons of waste rock (chat).

Mining companies would re-run the chat as many as three times in order to recover all the ore possible.

Sludge and mill waste were also recycled from mill sites.

Such recycling accounts for some of the variability in the level of lead found in the chat.

In 1946 the Tri-State Zinc and Lead Ore Producers Association lobbied the U.S. Congress for economic assistance to continue the mining of marginal ore deposits remaining in the mining district.

Although the Tri-State ore producers were not successful in their lobbying, assistance was provided by a production subsidy under the Strategic Minerals Act of 1949, which paid mining companies a subsidy for tonnage produced regardless of ore content.

This provided an economic incentive to remove pillars (support columns).

Removal of pillars fulfilled miners’ predictions of mines collapsing, water filling mine caverns, and contaminated acid water flowing into Grand Lake.

In 1958 many of the mining companies were shutting their doors and moving out of the field.

As each mine closed, the water level rose, and it became more difficult for those remaining to continue in business.

Eagle-Picher, the largest company in the area and the last to shut its doors, began subleasing to gougers in the late 1950s.

The gougers would enter the mines and mine out any ore remnants.

It was during this era that additional pillars were removed, thereby increasing the potential for subsidence of the surface above the mines.

Eagle-Picher opened up the first incline tunnel at the Swalley Mine northeast of Picher in 1969 through 1970.

The Kansas Health Department, due to the heavy iron ore and other minerals draining into Spring River and Lytle Creek, closed this operation.

The company invested more than $1 million trying to contain the water and reduce contamination problems.

The extensive mining in the Tri-State District left abandoned shafts and underground caverns extending from south and west of Commerce, Oklahoma, to Joplin, Missouri.

The caverns are not continuous; however, only small parcels of solid land exist in some areas, which could cause potentially hazardous situations.

MINING METHOD

A standard shaft was 5 feet by 7 feet encased in wood cribbing from hard rock to the top of the ground.

A 6 ½-foot round hole was made from the hard rock down to the mining level.

As modern equipment became available, larger holes were made (6 ft. by 9 ft. and 7 ft. by 8 ft.).

Mining was accomplished by the room and pillar method, which consisted of cutting open stopes with irregularly spaced pillars.

Generally, the ore body was crosscut by the shaft; therefore, the problem presented was how to mine the better grade of ore and leave only the lowest grade of ore for pillars to support the roof.

The structure and formations of the roof of the stope and the width and height of the ore body controlled the size and spacing of the pillars.

If the shaft had been completed in the ore body, stopes were opened up radially for the full height of the ore, with pillars 20 to 50 feet in diameter and properly spaced to support the roof, usually 30 to 100 feet apart.

About 15 percent of the ore body was left for pillars.

Later when the mine reserves were depleted, as much as 50 percent of the tonnage left in the pillars was recovered by slabbing operations or by complete removal of certain pillars.

The depth of mines varied in the mining fields according to the ore veins.

The average depth was 237 feet.

Shafts on the Kansas-Oklahoma state line in the central portion of the mining field were deep.

They became even deeper further north, with some mines extending down to 458 feet.

South of the state line mine shafts were shallower. Shafts in Hockerville, Commerce, Quapaw and Lincolnville were very shallow, from 78 to 120 feet deep.

Shafts in Douthat and southwest of Cardin were 200 to 290 feet in depth.

(Insert "Depth of Mine Workings and Shaft in the Picher Field" Map)

In the shallow mining area ore veins extended close to the surface and no cap rock was present, only shell rock.

It is in these areas that large cave-ins have occurred.

These areas will be a factor in addressing subsidence and mine shaft closure.

There are areas in the Picher Mining Field where large unsupported caverns exist that have shown no outward signs of subsidence.

This is due to a 30- to 40-foot solid limestone layer near the ground surface.

Some of the more productive mines had three levels of mining, and in some mines pillars in all three areas were removed leaving little or no support.

According to some former miners, a baseball game could be played in the open space and grass roots could be seen growing from the ceiling.

In some of these areas subsidence of 80 to 140 feet has already occurred, but the surface ground looks deceptively normal.

In other areas where the ceiling is only 15 feet high, subsidence or cave-ins leave only small, sunken areas on the surface.

Some of the larger caveins reach the surface resulting in as much as a 170-foot subsidence.

HISTORICAL SEALING METHODS

As the early mines began to close, several methods were initially used to cover the open shafts and protect people, livestock, and pets from falling into them.

In some cases old car bodies and railroad ties were used to seal the mine shafts.

These were temporary methods of closure.

However, these methods have been the only cover on some of the shafts for up to 60 years.

In 1936 Eagle-Picher sealed six mine shafts by drilling into hard rock and using steel bars to anchor a wooden form over which a concrete slab was poured.

Between 1956 and 1962 Eagle-Picher poured concrete shaft covers over five additional known mine shafts.

The Ottawa Reclamation Authority (ORA) sealed six shafts in the Picher area by building pyramid-shaped wooden forms holding six to seven yards of concrete.

After the concrete was poured, the forms were removed and the concrete slab was pushed over the opening to the shaft.

The hole was then backfilled to prevent ground water from entering.

Later the ORA used old cement mixer bodies instead of the wooden forms to plug three shafts.

Filled with concrete, the mixer bodies made adequate seals for the shafts.

The Authority also closed additional shafts using Haliburton oil tanks.

In January 2000 the Oklahoma Department of Environmental Quality (DEQ) and Grand Gateway Economic Development Association (GGEDA) sealed three mine shafts as a pilot project for future closure and sealing methods.

Each shaft required a different method of sealing

The first used the cement mixer body method,

The second was filled with large rocks from a nearby boulder pile, and the third was covered with a cement slab.

Total cost for the pilot closure project was $15,000.

Each of the methods is being evaluated for future use.

PREVIOUS STUDIES

The Luza Report, completed in 1986, identified 1064 shafts in northeast Oklahoma.

The report did not investigate areas within city limits.

However, different mine maps and interviews with former miners indicate there are more mine shafts, particularly within the city limits of each of the mining towns.

In 1998 the DEQ and GGEDA began a program to map and identify shafts, subsidence, chat piles, mill sites, and other mining hazards that exist in the mining field.

The mapping utilized old mining area maps, interviews with former miners and area residents, research at area universities and colleges, GPS location data, and fieldwork.

To date, the program has identified approximately 85 percent of the shafts in the northeastern Oklahoma mining field on hard copy maps.

MINE SHAFTS IDENTIFIED IN PREVIOUS STUDIES

Picher-Carden 212

Quapaw (city limits) 4

Commerce area 36

Peoria 4

Luza Report 1,064

Total 1,320

ANALYSIS

It is the opinion of Dr. Charles Nodler, Jr., archivist at Missouri Southern College (Joplin, Missouri), that there are possibly more than 300 shafts in the Picher-Cardin area alone.

And that in the mining district as a whole, which includes Kansas, Oklahoma and Missouri, there are in excess of 2,600 shafts.

Missouri Southern College has one of the most extensive collections of data pertaining to the mining district.

Lead & Zinc

Picher was the largest mining town in the country

Lead and Zinc Mining

The discovery of blackjack (a kind of zinc ore) on the Cook Forty in Galena in 1870 marked the beginning of a century of lead and zinc mining in the Kansas part of the Tri-State mining district. The Tri-State mining district of southwestern Missouri, southeastern Kansas, and northeastern Oklahoma was one of the major lead and zinc mining areas in the world. For one hundred years (1850-1950), the district produced 50 percent of the zinc and 10 percent of the lead in the United States.

Lead and zinc deposits in Kansas occur within the region called the Ozark Plateau in extreme southeastern Cherokee County. This region is defined by outcrops of Mississippian rocks (the oldest surface rocks in the state), which formed about 345 million years ago. The Ozark Plateau covers about 55 square miles in Kansas and includes the towns of Baxter Springs and Galena.

The first commercial ore discovery in the district was made in southwest Missouri around 1838. Production from the Tri-State district peaked between 1918 and 1941. There were more than 11,000 miners working in the area, and perhaps three times as many were involved in support work and industries.

Although zinc was much more common than lead throughout the Tri-State mining district, production up to 1869 was confined to lead, which could be easily smelted in homemade furnaces. Zinc production took off in the early 1870's, following the completion of railroad lines and the construction in 1873 of a coal-fired zinc smelter at Weir City, Kansas (fueled by coal from nearby mines). In 1878 another smelter was built at Pittsburg, Kansas. In the early 1900's, smelting costs were reduced by the discovery of a shallow gas field in southeastern Kansas. Using this cheap fuel source, new gas-fired smelters were built in southeast Kansas, displacing the coal-fired smelters.

During the life of the district, more than 4,000 mines produced 23 million tons of zinc concentrates and four million tons of lead concentrates. The Kansas part of the Tri-State district produced more than 2.9 million tons of zinc, with an estimated value of $436 million, and 650 thousand tons of lead worth nearly $91 million.

In general, mining was done underground, using room and pillar methods, in which room-shaped areas are mined and similarly shaped areas are left for roof support, resulting in a checkboard-like arrangement of alternating rooms and pillars. Underground rooms had walls 25 to 100 feet high and pillars 20 to 50 feet thick. In the eastern part of the district, however, the ore was closer to the surface. Surface mining was common around Galena, Kansas, which became known as a poor man's mining district because small claims could be easily worked.

Many of the rock layers that were mined for ore were also aquifers, or water-bearing formations. Thus, water often came into the mines through these rock layers. To keep the mines from filling with water, as many as 63 pumping plants operated 24 hours a day to remove huge amounts of water. For example, in 1947, more than 36 million gallons of water were pumped from the mines every day (this is enough to cover one acre of ground with water 110 feet deep).

After World War II, production in the Tri-State mining district gradually declined until 1970 when the last active mine, located two miles west of Baxter Springs, Kansas, shut down due to environmental and economic problems.

Environmental Consequences

Lead and zinc mining left behind a number of physical hazards and environmental problems. Over the years, physical hazards such as open mine shafts, collapsed mine shafts, and subsidence areas have claimed lives, caused property damage, and created avenues for water to enter and leave the mines. Subsidence was often a result of the final phase of mining, known as "robbing the pillars," which involved mining the pillars that supported the mine roof. Without these supports, the mine collapsed, eventually causing subsidence at the surface.

Subsidence feature from collapse of one of the deeper lead and zinc mines in Cherokee County.

In the early 1980's, the U.S. Bureau of Mines, in cooperation with state geological surveys, conducted detailed studies of the physical hazards associated with the old mining areas. The studies identified more than 1,500 open shafts and nearly 500 subsidence collapse features in the Tri-State. A total of 599 mine hazards were found in and around Galena, many of which were concentrated in an area known as "Hell's Half Acre." In 1994 and 1995, the U.S. Enivironmental Protection Agency (EPA) and local citizens filled in all the mine collapses and shafts in the town of Galena, Kansas. New top soil was hauled to cover the chat and boulders in the area.

The hundred years of mining also left the region with serious environmental problems. When the mines closed, the pumping stopped, and the abandoned tunnels filled with water. The water in these tunnels became contaminated by iron sulfide (from pyrite and marcasite), which remained in the mine walls or was left behind by the miners, as well as by other metallic sulfides found in the mines. In addition to becoming very acidic, the water contained dissolved metals, some of which are very toxic. This water, in turn, contaminated local ground water, springs, and surface water.

Water contaminated by iron sulfide flows into stream across the state line near Picher, Oklahoma.

Lead and zinc production involved crushing and grinding the mined rock to standard sizes and separating the ore. This left behind piles of leftover rock called tailings that covered 4,000 acres in southeastern Cherokee County. These wastes were also a source of contamination. Lead, zinc, and cadmium from the tailings leached into the shallow ground water, contaminating local wells, and runoff moved contaminants into nearby streams and rivers. Wind also blew fine metal-bearing dust (from tailings piles and roads made of tailings) into the air, spreading the contamination to nearby non-mined areas. Radon gas from the mining operations was detected in the air around Galena. During the 1980's, this area was considered one of the most environmentally blighted in the nation.

Some of the cleanup efforts are funded by the U.S. Environmental Protection Agency's Superfund. The EPA began working in the area in the early 1980's and work is ongoing. The EPA divided the Cherokee County Site into six subsites that correspond to six general mining locations, including the areas around Galena, Baxter Springs, and Treece, Kansas.

Because the area in and around Galena had some of the worst contamination, early cleanup efforts were centered there. Chief among these was the provision of safe water supply for rural residents whose wells had been contaminated. Two new wells were constructed in the deep aquifer, and a new rural water district was formed that currently provides over 500 households with a long-term source of clean drinking water.

From 1997 to 1999, contaminated soil was removed from 602 residential properties in Galena and replaced with clean backfill and grass sod or seed; fifty additional properites were remediated in 2000 and 2001. Remediation of residential soils has been completed in Treece and is ongoing in Baxter Springs. Cleanup continues at other sites in southeastern Kansas. For more information, check the EPA Region 7's website: http://www.epa.gov/region07/index.html.

Sources Buchanan, Rex C., and McCauley, James R., 1987, Roadside Kansas--A Traveler's Guide to Its Geology and Landmarks: Lawrence, Kansas, University Press of Kansas, 365 p.

EPA Region 7, Programs, Superfund, National Priorities List Fact Sheet, Cherokee County, Kansas: http://www.epa.gov/region7/cleanup/npl_files/ksd980741862.pdf (May 5, 2005).

McCauley, J. R., Brady, L. L., and Wilson, F. W., 1983, A Study of Stability Problems and Hazard Evaluation of the Kansas Portion of the Tri-state Mining Area: Kansas Geological Survey, Open-file Report 83-2, 193 p.

Pierce, Robert, 1995, Southeast Kansas--Coal Mines and Fossils: KESTA 4th Annual Fall Conference and Field Trip, October 20 and 21, 1995, Guidebook, 23 p.

The Picher Mining District occupying 40 square miles of northern Ottawa County, Oklahoma, was a primary source of lead and zinc to the U.S. from the early 1900's to the 1940's and is the largest superfund site in the U.S. Millions of cubic yards of mine tailings (locally known as "chat") remain in the area.

Although processed to remove metals, the chat is composed of chert, dolomite, calcite, and residual oxides and sulfides of iron, zinc, manganese, lead, cadmium, and other metals.

Some chat has been gradually removed from the area for use as gravel, concrete aggregate, and asphalt pavement.

Local residents have elevated blood lead levels and rates of kidney disease appear to be elevated.

Much of the area does not support vegetation, leading to suspension of fine sediment particles by winds.

Iron-staining of vegetation along local streams is notable.

Boulder of cherty dolomite from the Boone Chert of Mississippian age--the host rock for the ores.

Substantial amounts of concrete structures remain in the area, the concrete being made with chat.

Drainageway from chat piles to nearby wetland.

Concrete ore-separation tank near Commerce.

Wetlands draining mined areas south of Picher. The water table is within a few feet of land surface in much of the District.

Pond in chat may be a shallow depression or may be underlain by an open mineshaft. Subsidence is common in the area.

Chat commonly consists of boulders or fine particles ranging in size from small gravel to silt.

Chat has been used as aggregate for paved and unpaved roads in the area and perhaps on roads as far away as St. Louis and Oklahoma City.

Although this may appear to be a small pile of chat overlying a thin layer of chat, this 40-acre area near Picher is covered by a layer of chat 10-15 ft thick.

Surficial portions of chat piles are generally friable, but internal portions of the piles commonly become lithified.

Aside from scattered grasses and stunted trees, many parts of the area resemble a moonscape.

Nestled amongst these chat piles is a baseball field.

Another view of baseball field near Picher.

An old picnic site at the foot of a large chat pile.

The Picher mining district was known as "The Hay Capital of the World" prior to mining.

TRI-STATE TRIBUNE

Newspaper office in Picher on Connell Avenue behind the office there is a major underground rock fall which travels back west to the old baseball field between Connell Avenue and Main Street.

On the west edge of the baseball field there is a shaft that was filled with wood timbers and dirt many years ago.

BLACK HAWK MINE

Street Northeast of old U.S. 69 and present U.S. 69 junction in Picher, near the present business of the Picher Express

Pillars were shot away in later years.

There is a pull drift leading west from the mine to R. Harrell Park on S. Main Street, under which there is an unsupported cavern that the Astrodome would fit into.

Miners consider this area more hazardous than the area on N. Main Street that was condemned decades ago.

OLD BALL PARK

Center field area located directly west of Item 1 above

Large underground rock fall, roof height 100 ft. plus.

JOHN BEAVER-CRYSTAL-RITZ MINES up to VELIE LION-E-P

Cardin shops location, north and northwest of shops

All of these workings were mined to a very high roof.

Sheet ground (shale rock) in upper levels is very unstable plus lower levels made unstable by tar seams.

This collective area was considered the most dangerous to work in by the miners because of rock falls from the roof.

Their opinions agree with that reported by Ken Luza.

SYNDICATE MINE

Northwest of Picher High School toward Treece, Kansas, on the east side of Tar Creek

Very bad rock strata throughout, with very thin or no upper limestone supporting roof.

PIOKEE MINE (later named DEW DROP)

One block north of Picher High School

Had pillars removed by gouger mine operators in later years;

A cave-in exists on the east side of the mine, with residence within 100 ft. of the cave-in.

LUCKY BILL to RIALTO #1 and #2 to LUCKY BILL MINES:

One block south of S570R and E30R roads, RIALTO #1: east of Cardin on old U.S. 69 highway at College Street.

Junction, RIALTO #2 southeast of LUCKY BILL ¼ mile-pillars were removed and totally mined out especially around the shafts for a 200 yd. radius.

The roof gets higher from the RIALTO #2 toward the ADMIRALTY due south, where it was necessary to drill from 75 ft. high towers to reach the upper mine working face.

One miner exhibited a photograph of a miner standing on a 100 ft. tall ladder removing rock from the roof.

Another had a photo of the drilling tower as it was used in many mines having a high roof.

HUMBLE GRAVEL PLANT

Intersection of S. College Street in Picher and old U.S. 69 Hwy

Former location of RIALTO #3 Mill Shaft Site area under the Humble Gravel Chat Pile

Lacks support due to the absence of supporting limestone, and was mined up to the shale formation in many areas.

Reported early day cave-in before 1940 on the south side of the chat pile adjacent to the highway which filled itself in with chat from the chat pile.

ADMIRALTY #1, 2, and 3 MINES

East and southeast of Douthat, #2 is north of Douthat Rd, #1 and #3 are south of the road and connected underground to the SKELTON MINE

An unusual geological feature is found in these workings.

The Miami Fault Line Anticline was visible in the mine near #1.

Faults are known for slippage, especially during seismic activity.

All of these workings are located in sheet ground (shale) and were well known for dangerous underground cave-ins due to instability of the roof.

The deep water well casing was blasted and broken, permitting mine water to penetrate to the lower Roubideaux formation.

The condition of the well casing at the surface is unknown.

The well was located at the junction of the SKELTON & ADMIRALTY leases.

BECK MINE

Southward across East A Street in Picher to HUDSON MINE(11.), 1.5 mi. east of A Street

Connell Avenue junction. A cave-in on north side of road and connected underground to location where A Street caved in several years ago, resulting in one fatality.

Unstable rock strata with signs of surface sinking in the paved road.

HUDSON MINE

(see item 10 above)

BLUE GOOSE #2 MINE

West side of mine, 0.5 mi. north of Central Mill site

Caved in through the chat pile years ago, workings unstable and had many roof rock slabs fall during operating years.

(Note: The Blue Goose Mine is the mine that Mickey Mantle's father worked in, and during off season Mick also worked in)

GOODEAGLE MINE

0.75 mi. north, 0.25 mi. east of Central Mill
Although not connected underground to other mines, it was mined on multiple levels to a very high roof resulting in instability.

This type of mining without pillar support was most common in the Commerce area.

BENDALARI and CHEROKEE MINES

2 mi. west on 19th Street in Kansas Mine leases in this area were very unstable.

The former shaft was re-cribbed at the top five times due to poor stability of the upper rock strata.

Close to Tar Creek.

FEDERAL LUCKY MINE

Just west across Tar Creek from SYNDICATE on west side of the creek

Same problems as reported for the SYNDICATE MINE.

HOWE MINE

Northwest of PIOKEE and south of SYNDICATE on west side of Tar Creek approx.

10 blocks from Picher High School

Had very thin upper strata of limestone and poses a threat to Tar Creek if it subsides, since most of the creek would then run into the cave-in.

NEW PICHER BALL PARK

West two blocks on West A Street, south side of Netta Street and West A Street corner

Improperly filled shaft over a cavernous underground area not supported by pillars.

In a residential area.

DAVIS BIG CHIEF MINE and DAVIS WHITE MINE

0.5mi. north of U.S. 69-A Street, junction then 300 yds. West in Picher

These workings northward toward the KS-OK state line and southwestward were unstable due to tar seams and tar deposits all the way up to the “E” Boone Formation.

Miners report that the highway at the state line junction would be a very likely future subsidence location.

They report that they could hear trucks on the highway above them.

EMMA GORDON MINE

0.25 mi. west of Main Street in Commerce

Mining generally in the Commerce area was in very narrow drifts due to the nature of the ore deposits and lack of sound rock strata overhead for roof support.

Room and pillar mining method less used in the Commerce area and as a result, there have been several collapses over the years.

CATUS to JONES & GOLDBERG MINES

South edge of Commerce on old U.S. 66 Hwy

There is a shaft of unknown condition between these two mines not shown on the maps; its location is on the R22E-R23E section line.

Mined area of these two mines was at a shallow depth and not in sound rock formation.

Probably accounts for some of the past subsidence in this area.

Other mines, which have the potential for subsidence, but were not well documented by the miners were:

PICHER AREA:

SWIFT

KENOYER

PREMIER

SKELTON

SCOTT

SUNFLOWER

CARDIN AREA

BABY JIM

COMMERCE AREA

NEVER SWEAT

LAST CHANCE

COMMERCE MINING & ROYALTY

LINCOLNVILLE AREA

PETERSBURG

ROMO

SILVER STREAK

Very little information was obtained on mines in the Quapaw (Lincolnville) area.

The process of collecting, evaluating, and interpreting the large amount of map, borehole, and other data and information needed to conduct this subsidence evaluation has resulted in a number of findings and conclusions relative to the evaluation process.

These findings are applicable to any future subsidence hazard evaluations, geotechnical investigations, or land use planning that may be conducted within the 4,400-acre study area or the larger Picher Mining District.

Analysis of the data to yield estimates of the location and amount of possible subsidence within the study area and to derive a probability of subsidence at a select subset of these locations, has also lead to specific conclusions regarding subsidence and subsidence hazards in the area.

• 3,130 acres in the 4,400-acre study area were not undermined. However, 1,270 acres were undermined, of which 88 acres displayed greater than nominal potential for subsidence. The 88 acres found to display greater than nominal potential for subsidence were identified as 286 separate locations and/or clusters.

• Subsidence can occur with little or no advance warning.

• Methodologies are not currently available to accurately predict when subsidence will occur.

• 473 acres of the 1,390 acres of the town of Picher that are located within the study area are undermined.

• 17 acres of the 58 acres of the town of Cardin that are located within the study area are undermined.

• 25 acres of the 231 acres of the town of Hockerville that are located within the study area are undermined.

• The Subsidence Evaluation Team located no maps of mines in the vicinity of the town of Quapaw, and as a result, the extent of the undermining of Quapaw is unknown. The presence of mine shafts and mill sites in the area, however, indicates that significant mining may have occurred beneath the town.

• 4.5 miles of the 19 miles of major transportation corridors in the study area are undermined.

• 15 shaft related and 20 non-shaft related subsidences have occurred in the study area since the 1982 inventory by OGS.

• Factors identified as contributing most to non-shaft related subsidence are width of stope, height of stope, combined thickness of the Boone Formation and Chester above the stope, and depth of stope.

• Current groundwater levels in the study area provide a buoyant effect that reduces the effective load on remnant pillars and mine roofs and therefore may decrease the potential for subsidence.

• Mine maps are of different vintages and the most recent maps do not always include mine workings shown on older maps. Also, discrepancies exist between mine maps within the same lease.

• Map symbols used to indicate different mine levels can be inconsistent from lease to lease, and in some cases are inconsistent within the same lease.

• Interpretation of mine maps is sometimes difficult in areas of multiple-level mining because of overlapping and/or inconsistent map symbols.

• The mine floor and roof elevations can be estimated by using assay data from exploration borehole logs.

• The geology is variable within short distances, as indicated by the exploration borehole logs and available published reports.

• The extraction ratio for many of the mines, calculated from the detailed mine maps, is greater than 90%.

• There is very little existing geotechnical or rock mechanical data to assess the probability of subsidence using available analytical methods.

• There is very little documentation available regarding the shaving and removal of pillars, except for a few isolated cases.

• Details of the mechanics of non-shaft related subsidence in the study area are poorly understood.

• Post-mining subsidence features (post-1970) in the Picher Mining Field have tended to be smaller in size than previous collapses, perhaps indicating a differing collapse and subsidence mechanism than in the earlier collapses.

• Some existing houses in the Picher area most likely do not meet HUD requirements for habitability or for financing home improvements or sales.

• Some areas in the mining field are not suitable for residential or business development given the safety risks and the cost to mitigate them.

The above findings lead to the following conclusions regarding subsidence hazards within the study area:

• The potential for shaft related and non-shaft related subsidence is a very serious threat to the safety and economic well-being of people who reside in and travel through the area.

• The area exposed to subsidence hazards is a relatively small percentage of the total study area, but some residential and public-use areas and portions of transportation corridors are subject to some degree of subsidence hazard.

• 4,312 acres of the 4,400-acre study area are not subject to subsidence based on limited evaluation of available information from mine maps and conservative estimates of rock bulking factors. Further review of all available information may reveal additional areas subject to potential subsidence.

• Based on the back-analysis of failed mine workings, it is probable that additional non-shaft related failures will occur in the future.

• Every shaft has the potential to collapse, and the initial opening of a shaft collapse is likely to be the dimension of the shaft, and may grow as large as 30 feet in diameter.

• The quantifiable variables of 1) width of stope, 2) height of stope, 3) combined thickness of Boone Formation and Chester above the stope, and 4) depth of stope can be effectively used to estimate the probability of subsidence.

• A preliminary predictive tool has been developed that enables prediction of the probability of future subsidence potential in the Picher Mining Field.

• The magnitudes of possible subsidence at locations evaluated in this study range from less than 1 foot to greater than 50 feet, with the attendant possibility of loss of life and/or property, depending upon where the subsidence occurs.

• Land use determines the potential impact of a subsidence event on the population. For example, a one-foot subsidence in a road has more serious consequences than a similar or even larger subsidence in an agricultural area.

• Lowering of the groundwater table to levels below mine roof elevations may locally increase the probability of subsidence. This would probably only occur through pumping. However, water level fluctuations may cause increased shaft related collapses.

• A thorough evaluation of subsidence potential of a mined area must include a careful review of all available mine maps.

• It is likely that subsidence features exist in the study area that have not as yet been identified.

The Tri-State Lead-Zinc District in southwestern Missouri and adjoining parts of Kansas and Oklahoma, commonly known as the Tri-State District, was one of the foremost mining districts in the world.

The productive life of the district began with the discovery of lead near Joplin, Missouri, in 1848. A later discovery in Peoria, Oklahoma in 1891 led to the expansion of mining into Ottawa County (Neiberding, 1983).

However, the eventual depletion of high-grade ore deposits in the 1930s and the consequent lowering of the grade of mine-run ore caused a gradual and then marked decline in the Tri-State District’s output of lead and zinc until the early 1970s when the mining field closed. In most of the intervening years the Tri-State District produced more zinc than any other field in the United States, and it generally ranked third or fourth in the United States in lead production

Mining practiced in the Picher Mining Field is commonly referred to as random room and pillar mining, where rooms were excavated and pillars were left to support the mine roof.

However, the mining practice in the Picher Mining Field differed significantly from that in other parts of the United States due to the sporadic, nonuniform ore occurrence and the numerous companies that were involved with mining.

A typical, but by no means comprehensive, sequence of the primary mine cycle events involved:

1. Extensive exploration and laboratory assaying to determine the location and grade of ore within a given parcel boundary.

2. Setting up milling facilities and constructing shafts to access the ore body.

3. Primary mining of rooms while advancing away from the shafts to encounter and remove the high-grade ore.

The mining approach was left to the discretion of the underground superintendent (Ground Boss) such that pillar locations and sizes were a matter of personal experience and not based on any preconceived design.

Mining was particularly dangerous as evidenced by the following description of “ladder mining”:

Roof trimming ladders are made of selected spruce in 20-ft sections.

When a 5-section ladder is run out, four guy ropes equally spaced with two men to a rope are used to steady the ladder and tilt it carefully back and forth to cover a little more area.”, (Eagle-Picher,1943)

4. As mines became depleted of ore, a second stage of mining was performed by the mining companies, including pillar shaving (trimming) or complete removal of pillars left during primary mining.

After the mining companies were finished removing the higher-grade ore, the mine workings were often subleased to independent miners (known as “gougers”) who removed the last remnants of ore from the roof, walls, pillars, and floors.

The outbreak of World War I increased both the demand and prices for zinc and lead, fueling expansion of the Picher Mining Field.

The 1920s were the golden years for the Tri-State District, with peak mine production being attained in 1925–1926.

During this period, electric power became available throughout the Tri-State District.

Mining and milling practices were further advanced with such innovations as the use of central air-compressing plants and the widespread use of froth-flotation in 1924 by the concentrating mills.

Zinc and lead recovered by reworking tailings became an important factor in the total production.

The flotation process could recover an additional 25 percent of zinc and 10 percent of lead.

The depression years of 1930 to 1939 saw the demand drop for zinc and lead products, with their values being reduced to less than the cost of production.

Due to low ore prices in 1931, all but four mines closed and the mining field was allowed to flood.

Mine production declined from a high of 10 million tons in 1925 to less than 2 million tons during 1932.

Many mining companies could not afford to continue pumping water from the mines during the depression and ceased operations altogether, never reopening some of the mines.

Beginning in 1933, the values for zinc and lead began to increase slowly, and by 1939, the district’s production was up to about one half its former averages.

World War II once again increased the demand for zinc and lead during the 1940s.

Although the federal government froze most prices and wages in 1942, it instituted a “Premium Price Plan” to encourage mining the lower-grade ores.

With this plan, mine production again boomed, reaching more than 9 million tons per year during 1943–1944.

During World War II, the level of ore production increased, but never duplicated the glory days of the 1920s.

After the end of the war, mine production began a slow decline.

Although briefly interrupted during the Korean War, the decline continued until 1957, when most of the larger companies ceased operations.

In addition, lead usage was coming under attack from poisoning problems related to paint pigments, printer’s ink, glass and ceramic ware, and anti-knock gasoline.

Zinc use suffered from substitution by plastics, aluminum, and epoxycoatings.

The principal market left for lead was the lead-acid storage battery; while zinc continued to be used for steel galvanizing, paint pigments, rubber curing, and die-casting.

By 1959, total crude ore production in Ottawa County was only 15,365 tons.

As lead and zinc demand dropped, economic hardship fell upon mining communities of the Tri-State District.

In April 1959, a congressional delegation visited the mining area, touring the zinc and lead properties surrounding Picher and visiting the Joplin mining area.

The hope was that help from Washington might pump new life into the zinc and lead mines.

The grim story of unemployment in the mining field was told before the House Interior Subcommittee in Miami.

The testimony given at the hearings by mine operators, miners, business representatives, labor, and social agencies in relating the consequences of mine and mill shutdown had an apparent impact on Congress.

The following year, Congress passed the Small Producers Lead and Zinc Mining Stabilization Act (the Act) to provide an economic stimulus for the Tri-State District.

Under the program established to implement the Act, groups of miners formed companies and produced crude ore from many formerly abandoned mines under a subsidy from the federal government.

Typically, these companies rented the mining equipment already in place and milled their ore at the central mill or at the sublessor’s mill on a toll basis.

As a result of this small producers’ program, total crude ore production in Ottawa County increased to about 500,000 tons per year during the mid-1960s but decreased rapidly as the program was phased out later in the 1960s.

By March 1964, only 281 miners were engaged in the mining industry of Ottawa County (Stroup and Stroud, 1967).

By the end of 1967, Eagle-Picher was operating only one mine. Gougers were mining most of the ore.

As a result of the selective mining techniques and the lack of discovery of new ore bodies, the Picher Mining Field continued to decline until its final closure in 1970.

At a few places in the Picher Mining Field, sharply defined structural features are accompanied by appreciable dips.

The Miami Trough, Bendalari Monocline, and Rialto Basin are three prominent structures that dominate the main part of the Picher Mining Field.

The Miami Trough is a combination syncline and graben that crosses the western part of the Picher Mining Field with an average trend of N 26o E.

The width of this structure is 300 to 2,000 feet, averaging about 1,000 feet.

The maximum vertical displacement is about 300 feet.

The Bendalari Monocline crosses the mining field with a northwest strike and drops the mineral-bearing ground a maximum of 140 feet on the northeast side.

The maximum dip is about 20o.

Chesterian strata are preserved in greater thicknesses on the downdropped side, and the structure is hardly noticeable in Pennsylvanian strata.

The Rialto Basin is an irregular, easttrending, faulted syncline nearly a mile long and as much as a quarter of a mile wide.

It has a maximum displacement of 80 feet and contains a thicker sequence of Chesterian strata than is found in areas outside the basin (McKnight and Fischer, 1970).

The linear structural features, such as the Miami Trough, are of tectonic origin and probably have been modified by some dissolution of carbonate rocks at depth, resulting in additional subsidence.

The Rialto Basin and smaller basins may have developed where dissolution along deep-seated fractures was accompanied by subsidence (McKnight and Fischer, 1970).

2% IN 50 YEARS PE ACCELERATIONS FOR PICHER, OK REGION: 94.85ºW, 37º N

PGA 0.059 - 1 Hz SA 0.071 - 5 Hz SA 0.142 - 10 Hz SA 0.127

The motions in Table 3.1 correspond to acceleration on a rock site with assumed shear-wave velocity of 760 meters per second in the upper 30 meters.

This velocity is roughly equivalent to the National Earthquake Hazards Reduction Program’s B (rock)-C (very dense soil or soft rock) boundary.

For perspective, a horizontal PGA of about 0.2 g is generally required to knock objects off shelves; 0.1 times the value of gravity is sometimes used as an approximate lower limit for damage to unreinforced masonry such as brick chimneys.

Such estimates are rough, and local site conditions will affect any estimated damage distribution.

Figure 3.3 is a map of the probability of experiencing, in any 100-year period, an M 4.75 or greater earthquake within 50 km of each site on the map.

Picher, located at the center of the map, is in a regional “seismic cold spot” according to the USGS seismic hazard model, with a probability of less than 0.01 (1 chance in 100) of experiencing such an earthquake.

According to the USGS model (Frankel et al., 2002), most of the seismic hazard at Picher is posed by distant seismic sources, in particular, the New Madrid Seismic Zone (NMSZ), about 260 miles east of Picher.

Large magnitude seismic events on the NMSZ have an expected recurrence interval of about 500 years and an estimated typical magnitude of about M 7.7.

A very small contribution (about 1%) of the seismic hazard also comes from the Meers Fault in southwest Oklahoma.

This fault zone, at about the same distance from Picher as the NMSZ, has a much longer mean recurrence interval, and the maximum credible earthquake is estimated to be smaller (about M 7.0) than the NMSZ main shocks.

Because Meers Fault earthquake would typically be of lesser magnitude and longer frequency than New Madrid events, its contribution to the seismic hazard is very small.

Another possible source zone that potentially affects the seismic hazard in northeast Oklahoma is the Saline River source zone (SRSZ) in east-central Arkansas.

This source zone is currently considered to be somewhat speculative, and for this reason was not specifically included in the USGS seismic hazard assessment of Frankel et al. (2002).

Evidence from paleoseismology includes sand blows and dikes in cutbanks in Ashley and Desher counties, but this evidence cannot be conclusively associated with the postulated SRSZ (Cox et al., 2004).

In conclusion, the seismic hazard in the Picher, Oklahoma area is considered to be very low according to the USGS seismic hazard model, with a probability of less than 0.01 (1 chance in 100) of experiencing an earthquake of magnitude 4.75 or greater within any 100–year period.

Groundwater is the primary source of water within the study area.

Three primary aquifers are present within the study area.

Two of the aquifers, the Boone and the Chat, are shallow and the water is not potable.

The recently identified Chat Aquifer is an artificially created, unconsolidated surficial aquifer composed of mine tailings distributed over much of the Picher Mining Field (Becker, 2005: personal communication).

Thicknesses range from just a few feet to several hundred feet where large piles still exist.

Recharge over the Chat Aquifer is rapid due the relative textural homogeneity and unconsolidated nature of the material.

Base flows in Tar and Lytle creeks are generally sustained through the mining area by discharge from this surficial deposit.

However, most of the domestic, municipal, and industrial supply is from the deep Roubidoux Aquifer.

The Roubidoux Aquifer underlies the Boone Aquifer and is generally a fractured cherty dolomite interbedded with thin sandstones.

Uppermost portions of the Roubidoux Aquifer are less permeable, which therefore restricts vertical movement of water from the Boone into the Roubidoux Aquifer.

Large municipal and industrial withdrawals have lowered the water levels in the Roubidoux from pre-pumping levels where wells were artesian to 300 to 500 feet below land surface.

Roubidoux supply wells in the mining area are often drilled to a depth of 900 to 1,100 feet and are cased to the base of the Boone Aquifer.

Water was withdrawn from the Roubidoux Aquifer when mining was active to supply mills and flotation-separation activities.

The Boone Aquifer consists of the Boone Formation where most of the ore occurred.

Large amounts of water were withdrawn from the Boone Aquifer to allow for access to the ore deposits during the period when the Picher Mining Field was being mined.

Cessation of dewatering activities resulted in the recovery of water levels to their current elevations above the mine-roof elevations.

The equilibrium of water levels has been maintained through discharges from mine shafts, vent holes, abandoned wells, and exploration holes whose openings to land surface are below the water level elevation of the Boone Aquifer.

Groundwater elevations in the Boone Aquifer indicate a very subtle north to south gradient.

Recharge to the Boone Aquifer occurs rapidly following precipitation and continuous recording wells in the mine workings indicate that the mines are hydraulically connected with elevations generally maintained at 795 to 805 feet above mean sea level.

Groundwater movement between the Boone and Roubidoux aquifers was likely minimal prior to mining activity.

However, it is estimated that hundreds of water supply wells were drilled through the Boone Formation and into the Roubidoux Aquifer to supply mills and towns with good-quality water.

Due to the current elevation differences of water levels between the Boone and Roubidoux aquifers, there is a downward flow gradient.

Over time, casings and cement seals in the Roubidoux wells will become compromised and allow contaminated mine water from the Boone Aquifer to flow into the wells and then downward to contaminate the Roubidoux Aquifer.

The EPA and ODEQ have been working since the 1980s to locate and plug these wells.

Open mine shafts and subsidence features in the area used for the dumping of trash are an additional potential source of contamination to the Boone Aquifer.

Becker, Mark, 2005, Personal Communication

Brockie, D. C.; Hare, E. H., Jr.; and Dingess, P. R., 1968, The geology and ore deposits of the Tri-State District of Missouri, Kansas, and Oklahoma, in Ridge, J. D., editor, Ore deposits of the United States, 1933-1967: American Institute of Mining, Metallurgical, and Petroleum Engineers, v. 1, p. 400-430.

Cox, R.T., Larsen, D., Forman, S.L., Woods, J., Morat, J., and Galluzzi, J., 2004, Preliminary Assessment of Sand blows in the Southern Mississippi Embayment, Bull. Seis. Soc. Am., 94, p. 1125-1142.

Fowler, G. M., and J. P. Lyden, 1932, The ore deposits of the Tri-State District (Missouri, Kansas, Oklahoma): American Institute of Mining and Metallurgical Engineers, Technical Publication 446, Class I, Mining Geology, No. 39, p. 49.

Fowler, G. M., 1942, Ore Deposits in the Tri-State zinc and lead district, in Newhouse, W. H., editor, Ore deposits as related to structural features: Princeton University Press, p. 206-211.

Frankel, A. D., Petersen, M.D., Mueller, C. S., Haller, K. M., Wheeler, R. L., Leyendecker, E.V., Wesson, R. L., Harmsen, S. C., Cramer, C. H., Perkins, D. M., and Rukstales, K. S., 2002, Documentation for the 2002 Update of the National Seismic Hazard Maps, U.S. Geological Survey Open-File Report 02-420.

McKnight, E. T.; and Fischer, R. P., 1970, Geology and ore deposits of the Picher field, Oklahoma and Kansas: U.S. Geological Survey Professional Paper 588, p. 165.

Oklahoma Climatological Survey, 1973.

Reed, E. W.; Schoff, S. L.; and Branson, C. C., 1955, Ground-water resources of Ottawa County, Oklahoma: Oklahoma Geological Survey Bulletin 72, p. 203.

Siebenthal, C. E., 1908, Lead and zinc, Mineral resources of northeastern Oklahoma, in Metals and non-metals, except fuels, pt. 1 of Contributions to economic geology, 1907: U.S. Geological Survey Bulletin 340, p. 187-228.

Weidman, Samuel; Williams, C. F.; and Anderson, C. O., 1932, The Miami-Picher zinc-lead district, Oklahoma: Oklahoma Geological Survey Bulletin 56, p. 177.

There are two primary categories of subsidence associated with underground mining.

The first category is called “chimney”, or “plug” subsidence, and is characterized by shearing, steep-sided depressions, and large-differential displacements.

The subsidence features formed by this mode of subsidence are commonly referred to as sinkholes, but the term “chimney subsidence” is used in this report to differentiate mine subsidence events from naturally occurring sinkholes that form in karstic limestone deposits.

Mine roof failure may or may not propagate to the surface to form chimney subsidence depending upon several factors, including the depth and height of the underground opening, the strength characteristics of the immediate roof and overlying rock mass, and the bulking characteristics of the overlying rock mass.

The second category of subsidence is termed trough subsidence, and is typically characterized by a broad, shallow, trough-shaped depression that forms above a mine opening when the overlying strata sag into the mine void with minimal shear displacement.

This type of subsidence is commonly associated with longwall coal mining, where a very wide area of coal (300 to 1,000 feet), called a panel, is extracted without leaving pillars or artificial support and the overlying material is allowed to displace downward into the mined panel behind the advancing mine face.

The potential for trough subsidence over room and pillar mines is dependent upon the stope geometry (width, length, and depth), extraction ratio, and the stability of the mine pillars, roof, and floor.

Although it is likely that trough subsidence has occurred in the Picher Mining Field, it is currently not well recognized or mapped.

Chimney subsidence is considered to be the primary category of subsidence in the study area, and by its nature imposes the greatest hazard to public safety.

There are two types of subsidence features that have been widely observed throughout the Picher Mining Field and in the study area – shaft related and non-shaft related subsidence.

Non-shaft related subsidences are believed to be predominantly of the chimney category that result from the collapse of mine workings.

This section of the report discusses these subsidence types in greater detail, summarizes the primary factors influencing subsidence, provides a brief overview of available subsidence analysis methods, and introduces the subsidence evaluation method chosen for application in the study area.

The random room and pillar mining method used in the Picher Mining Field resulted in the excavation of irregular shaped stopes, or rooms, and interconnected underground haulage ways that were ultimately abandoned as mining in the area ceased.

Often these stopes were quite large in both lateral dimension and height.

The presence of such large excavations at relatively shallow depths made the areas above the stopes vulnerable to subsidence in the event of collapse of the underground workings.

Pillar shaving and removal that was commonly practiced during the late stages of mining to recover economical ore resulted in unusually high extraction ratios for room and pillar mining and increased the potential instability of the excavations.

Later pillar shaving, pillar removal, and mining of small pockets of ore by independent miners further aggravated the stability of the mine workings and increased the potential for subsidence.

Because of the widespread mining activities, the large number of mining leases, and multiple mining companies involved in mining the Picher Field, a large number of abandoned mine shafts are also present throughout the study area. Many of these mine shafts have collapsed in the past, and remaining shafts are prone to future failure and subsequent subsidence.

Three stages of shaft related collapse and subsequent subsidence have been described in the Picher Mining Field (Luza, 1986) and are an operating shaft that is timber lined through the relatively incompetent overburden (e.g., alluvium and shale) and extending to the mine floor.

The shaft is not lined where it passes through the more competent portions of the overburden (e.g., limestone and chert).

Two or more mine pillars were typically left around the base of the shaft to provide extra support and prevent shaft failure and subsidence during active use.

After mining ceased in a given area and a shaft was no longer required for access or ventilation, it was typically abandoned. Figure 4.1b shows an intermediate stage of shaft collapse, where the upper support timbers have rotted out or been removed, a later stage of collapse where the lining has completely failed and the weak overburden has collapsed to fill the shaft.

This type of subsidence may or may not be coupled with stope roof failure, as discussed below.

The shaft failure sequence illustrates the impact of surface drainage on the shape and size of a subsidence feature, where the erosion of exposed rock and/or alluvium will, with time, increase the lateral dimensions of the subsidence.

A third, hybrid, type of subsidence, where pillars were removed from around abandoned shafts by gougers who accessed the underground workings from adjacent mine leases, has been observed.

This practice typically led to direct subsidence of the surface and, in at least one case, resulted in the formation of a very large subsidence area (Keheley, 2005: personal communication).

Subsidence has continued above the mine workings in the Picher Mining Field from shortly after the onset of mining to this day.

Luza (1986) compiled an inventory of shaft related and non-shaft related collapses that occurred prior to 1982.

An inventory of shaft collapses and non-shaft related collapses that have occurred since 1982 has been maintained by one Subsidence Evaluation Team member (Keheley, 2005), and is reproduced in Table 4.1 and Table 4.2.

These later collapses tend to be smaller in size than many of the collapses that occurred prior to the end of mining in the area.

The mine related surface impacts outlined above occur throughout the lead-zinc mining areas of Oklahoma, Missouri, and Kansas and have been investigated, characterized, and catalogued over the 35-plus years since mines in these areas were abandoned.

The extensive survey of mine subsidence features in the current study area, originally published by Luza (1986), has recently been updated with location information incorporated in this study.

However, there is little published information regarding subsidence analysis or subsidence prediction in the Picher Mining Field, and there has not as yet been an attempt to complete a systematic analysis of subsidence potential in the study area.

Case Number Shaft Related Collapse

1 Sooner tailings pile shaft No. 5-Dec. 2001. S16 T29N R23E.

2 Velie Lion shaft No. 37-Between 1982 and 2000. Elliptical collapse-approx. 60 x 80 feet x 35 feet deep. S19 T29N R23E.

3 Harrisburg shaft No. 44-Dec. 2002. Circular collapse expanded to approx. 80 feet in diameter x 70 feet deep. Collapse remains active. S19 T29N R23E.

4 Craig Lease Shaft No. 20- Dec 2003. Circular collapse 12 feet in diameter x 4 feet deep. S33 T29N R23E.

5 Craig Lease shaft No.15- Partial collapse 2002-12 feet in diameter x 4 feet deep (North side of lease in pasture adjacent to E40 Rd.). S33 T29N R23E.

6 Warner Fee (Commerce) Shaft No.1-January 2005. Circular collapse 10 feet in diameter. S6 T28N R22E.

7 Beck shaft No. 16-partial collapse beginning in 2001- 10 feet diameter x 8 feet deep. The shaft has continued to deepen. S29 T29N R23E.

8 Lucky Jenny shaft No. 11 (Hockerville)-late 2004 or early 2005. Circular collapse 50 feet diameter x 40 feet deep. S14 T29N R23E.

9 Mahutska Lease shaft No. 10 in the tailings pile-between 1982 and 2004. Circular collapse in tailings pile approx. 60 feet in diameter. S21 T29N R23E.

10 Partial collapse of Shaft No. 31 on the Barbara J Lease adjacent to Hwy 69-Occurred in 2001. Circular collapse 10 feet in diameter x 6 feet deep. S29 T29N R23E.

11 Shaft No. 34 fill material collapsed on the Beck Lease adjacent to ‘A’ Street. Concrete collar intact. Date unknown. S15 T29N R23E.

12 Shaft No.17 on the Missouri Mule Lease-Occurred around 2000. Circular collapse 20 feet in diameter. Water level 10 feet from surface. S28 T29N R23E.

13 SHAFT No. 10 on the New Chicago No. 2 Lease-Occurred in 2002. Circular collapse 20 feet in diameter x 15 feet deep. S28 T29N R23E.

14 Shaft No. 19 on the Ritz Lease in the road on Ash Street, south of Cardin Road, one block south of the old Eagle-Picher Office/Shop site. Occurred 1982. Approx. 40 feet in diameter x 30 feet deep. S30 T29N R24E.

15 Unnumbered shaft adjacent to Hwy 137 in Quapaw. Occurred in 2003. Approx. 15 feet in diameter x 30 feet deep. S35 T29N R23E.

1 Scammon Hill- Near shaft No.12- small elliptical collapse adjacent to collapsed shaft. Approx. 20 feet In diameter x 8 feet deep. S36 T29N R22E.

2 Scammon Hill- Near shaft No. 8-small circular collapse near shaft. Approx. 30 feet in diameter x 15 feet deep. S36 T29N R22E.

3 Massel Lease-two small collapse features adjacent to mill concrete pillars. Approx. 20 feet in diameter x 15 feet deep. S23 T29N R23E.

4 Scott Lease-Circular collapse 20 feet diameter x 10 feet deep. Water level at 10 feet- Jan. 2003. S13 T29N 23E.

5 Howe tailings pile-circular recollapsed around 1997. Expanded to 42 feet in diameter by 2001. S17 T29N R23E.

6 Drill hole collapsed in James Cruzan’s yard in Picher-2004. Approx. 6 feet x 8 feet S17 T29N R23E.

7 Collapsed drill hole on the Ruth Goodeagle lease approx. 100 yards. SE from shaft No. 3. Occurred in 2003. Approx. 2 feet x 8 feet S34 T29N R23E.

8 Elliptical collapse in the pasture 100 yards. east of S590 Road. Occurred in 2003. 12 feet x 15 feet by 10 feet deep. Collapse continues to increase in size. Also a drill hole collapse 100 feet NW of the elliptical collapse. S34 T29N R23E.

9 Martha B Mine, State Line Road-8 feet collapse 4 feet deep-January 29, 2005. Large depression 25 feet in diameter x 2 feet deep adjacent to the collapse. May be karst feature? S17 T29N R24E.

10 Small collapse in S590 Road on the Dardene Lease between Sections 21/22 T29N R23E. Approx. 4 feet in diameter x 8 feet deep-2004. Collapse filled with boulders by the County road crew.

11 Collapse 1531 on the Consolidated Lease west of Commerce. Filled after 1982. In a state of major collapse in 2005. S1 T29N R22E.

12 . Circular collapse 100 yds. Northeast of Velie Lion mill site-70ft in diameter x 30 feet deep. S19 T29N R23E

13 Collapse on the J. E. McGuirk Lease on the north side of E40 Road (Blue Hole Road) – Occurred Approx. 1982. Approx. 30 feet in diameter by 15 feet deep. Rural water system had to be permanently rerouted around the opening. S30 T29N R24E.

14 Large collapse 300 feet west of police station in Commerce-50 feet wide x 70 feet long x 140 feet deep. 1994-1995. S1 T29N R22E.

15 North side of ‘A’ Street 1.5 miles east of Picher-1992. Size unknown.

16 Small circular collapse on the Alice Greenback Lease adjacent to Hwy 69A NE of Quapaw. Approx. 4 feet diameter x 6 feet deep. Hole collapsed 3 times in 2004. S26 T29N R23E.

17 Old Hwy 66 in Commerce at the intersection of current Main Street and “C” Street-Drill hole in the center of the road 6 feet wide x 22 feet deep 1994. S1 T29N R22E.

18 Small circular collapse on the Skelton Lease adjacent to Hwy 69 on the east side, south of Picher- March 2005. Approx. 12 feet in diameter x 6 feet deep. S28 T29N R23E.

19 Circular collapse in S ½ of SE ¼ of Section 20 T29N R23E-5/8/83. Approx. 60 feet in diameter x 30 feet deep.

The following generalized description of mine roof failure is intended to provide a non-technical explanation of the mine collapse processes believed to be responsible for non-shaft related subsidence in the Picher Mining Field and the study area.

A detailed account of mine roof failure mechanisms and the theoretical basis for roof failure analyses is beyond the scope of this report, but detailed theories on mine roof failure and stability analysis can be found in numerous publications (e.g., Brady and Brown, 2004; Obert and Duval, 1967).

In general, the mine roof and overlying strata in a horizontally or near-horizontally bedded rock mass can be considered as a sequence of plates (in three dimensions) or beams (in two dimensions).

The thickness of each plate or beam is determined by the geologic contacts between rock units of similar strength and mechanical properties.

The thickness of each bed and the rock strength determine the overall strength of the plate or beam. Geologic layers that bond to overlying or underlying strata of similar properties can be grouped as thicker, and thus stronger, plates or beams.

A simple beam analogy is the use of multiple layers of lumber to form load-bearing headers above windows or doors in home construction.

As an opening is developed underground, the width and length of the unsupported roof increases.

If the opening dimensions get too large, the immediate mine roof (e.g., the first layer of rock) cannot support itself and fails.

Obviously, more competent roof materials and more massive and continuous strata allow wider rooms to be excavated without roof failure.

Prior to mining, rock at the mining level is subject to both a vertical stress due to the weight of the overlying rock (gravity load) and a horizontal stress that results from the rock’s reaction to the vertical stress.

These stresses may or may not be modified by tectonic activity, rock dissolution, or other geologic processes.

During and after excavation of an underground opening, stresses can not be transmitted through the void that is created, and vertical stress is transferred to the adjacent rock that forms the sides of the opening.

This stress transfer is commonly conceptualized as occurring through a pressure arch that forms above the opening in the overlying rock mass (see Figure 4.2a). Thus, the load carried by the immediate roof is limited in that it carries only its own weight and some portion of the weight of material below the pressure arch, but does not carry the total overburden load.

This same concept applies to room and pillar mining when the pillars are too small (either by design or by shaving and/or removal of adjacent pillars) to carry the total overburden load.

Under high loads relative to the strength of the pillars, the pillars deform or yield, resulting in stress transfer and the extending of the pressure arch to the sides of the opening or to larger adjacent pillars

This process is believed to be why some very wide rooms that were developed during primary and secondary mining in the study area have apparently not collapsed.

As the dimensions of the underground opening increase, the pressure arch increases in height.

During this process, the thickness of rock supported by the pillars under the pressure arch increases, causing increased pillar stress.

As the room width and corresponding height of the pressure arch increase, the pressure arch ultimately intersects the weaker, overlying strata (i.e., the shales, sandstones, and alluvium in the study area).

Because these weaker materials cannot effectively support a pressure arch, the pressure arch breaks down and the pillars become subjected to the full overburden load.

At some point, when the vertical stresses cannot be effectively transferred to the edges of the workings, the pillars may fail, leading to massive (i.e., large, contiguous areas) roof falls and possible caving and void propagation toward the surface

These conditions are believed to be present to various degrees throughout the study area.

Several physical and mechanical factors may influence mine roof failure and resulting subsidence in the study area. Upward migration of the void initially begins with failure of the immediate mine roof, which is typically a function of the width and length of the opening and the strength and thickness of the rock mass forming the immediate roof.

The void may propagate rapidly to the surface or take several decades to propagate to the surface and cause subsidence.

The propagation rate and distance above the mine opening to which the void ultimately propagates depends primarily on the depth of the opening and the characteristics of the overlying rock.

The strength of the rock that forms the immediate mine roof is a primary factor in mine roof stability.

The strength of the mine roof is also generally proportional to the thickness of the rock layer comprising the roof.

Most of the mining in the study area took place in the Boone Formation, which is predominantly composed of bedded chert, a relatively high strength siliceous rock.

The Boone Formation is in turn overlain by the Quapaw and Hindsville Limestones that in most locations are not as strong as the Boone chert, but stronger than the composite overlying shales, interbedded sandstones, and alluvium.

In some locations mining extended upward into the limestones above the Boone Formation, and in some cases into the overlying sandstone and shale.

Mine roof rock in these areas would thus be much weaker and such areas would be more prone to roof failure and subsidence than areas where mining was entirely confined to the Boone Formation.

Roof rock strength can also be significantly degraded by the degree and orientation of natural fractures and joints present in the rock.

Details regarding the geology and degree of fracturing in the study area are not available except for one or two mining leases.

Secondary mining was practiced throughout the Picher Mining Field during the major mining periods as well as toward the end of mining in 1970.

However, the largely unregulated shaving and removal of pillars that occurred toward the end of the mining era likely increased the subsidence potential above that present following the primary and more controlled secondary mining done by the mining companies.

In general, pillar shaving reduces the load-bearing area of the pillars and increases pillar stresses, potentially leading to pillar yield and/or failure.

Transfer of stresses from yielding or failed pillars to adjacent pillars results in an overall decrease in opening stability.

At some point in this process stope width would become a limiting factor with regard to stope roof stability, and ultimately caving and subsidence potential.

Complete removal of pillars results in large unsupported spans and leads to the modes of failure described above.

Blasting, especially over-blasting, produces fractures which weaken the outer portions of a pillar and consequently reduce the effective area through which overburden loads can be supported.

This reduction in load carrying area results in increased pillar stresses in the central, undamaged portion of the pillar.

Thus, pillars subjected to blasting damage, either as a result of original mining or subsequent shaving, may actually yield and fail well before what would otherwise be expected based on the size of the pillar.

Similarly, blasting to excavate a shaft can also have a detrimental effect on the strength of rock surrounding the shaft.

Thus, locations where mine shafts penetrate a mine roof may also be local areas of weakened mine roof rock and potential roof instability.

The inundation of the mines following the end of mining has likely had a stabilizing effect on the abandoned mine workings.

Hydraulic pressure from the groundwater within the mines provides a buoyant force that helps to support the overburden and reduce the vertical stresses on the roof and remaining mine pillars.

The abandoned mines in the study area are currently flooded and submerged below more than 75 feet of water.

The groundwater level is at about 800 feet elevation and fluctuates from 790 to 805 feet as measured in the Blue Goose mine shaft (EPA, 1994 - Tar Creek Five Year Review).

Significantly lowering groundwater levels below these elevations, either due to climatic conditions or human activities, may increase the potential for mine collapse and subsequent subsidence through several processes, as briefly discussed below.

Increased Pillar Stress: Significant lowering of water levels in the mines would reduce the buoyant forces acting on the mine roof and effectively increase the vertical load on the roof pillars, potentially leading to increased instability.

Volume Change: Lowering of the water table would likely decrease the moisture content of the overlying shale.

Reducing the moisture content of shale typically causes shrinkage (volume reduction), which could lead to tensile stresses, cracking, and reduction of lateral confinement of the shale rocks overlying the mine workings.

This shrinkage and cracking would likely reduce the effective strength of the shale overburden and increase the load on the non-shale mine roof rock.

Slaking: In some shales and volcanic rocks, radical deterioration in the rock quality and strength properties can occur after a rock surface is exposed to the air, either due to excavation or dewatering.

Repeated cycles of wetting and drying can lead to significant strength reductions of shaft and existing subsidence walls, which could contribute to shaft related collapse and enlargement of existing subsidence features.

Lowering of groundwater levels below the upper levels of mining in the study area is unlikely, but could also lead to significant strength reductions of the mine roof where the roof is located in or near the overlying shale.

Strength reduction of limestone or chert owing to exposure to air would not be expected.

As discussed above, lowering of the groundwater table in the Picher Mining Field may accelerate the incidence of subsidence throughout the project area.

It has been observed that the incidence of shaft related failures increases (Keheley, 2005, personal communication) during periods of drought.

This observation is also consistent with experience that natural sinkholes often occur in karstic terrain during periods of drought and groundwater decline.

Section 3 summarizes the probability of significant seismic events in the study area.

Projected Seismicity is low and any related effects are expected to be minimal.

In addition, the impact of seismic effects on underground excavations is typically less pronounced than at the ground surface. Seismicity is therefore not expected to be a significant factor contributing to future subsidence potential in the Picher Mining Field.

Surface land uses will usually have little effect on underground roof or pillar stability.

However, the large mine waste or chat piles that remain in the area will continue to contribute to pillar loading, especially when underlain by laterally extensive mine workings.

Deep surface excavations could also have undesirable consequences on subsidence potential if they were to disturb remnant pressure arches and induce local mine roof failure and caving.

Loading and vibrations from vehicles traveling on overlying roads are thought to have minimal effect on subsidence potential.

However, the potential effects on subsidence of dynamic loading from vibrations caused by heavy truck traffic on irregular or uneven road surfaces are not well known and could be of concern in areas where roadways pass over shallow mine workings

The role that pillars play in determining the overall stability in a given stope or mining area was discussed in Section 4.4.2.

In the Picher Mining Field, a stope may be defined as a room-and-pillar area surrounded by solid ground, or as an area supported by small or widely spaced pillars that is surrounded by solid ground and/or larger or more closely spaced pillars.

Defining such areas on mine maps is inherently subjective.

In the case of a room and pillar area surrounded by solid ground, failure of individual pillars would transfer load to adjacent pillars that may subsequently fail, leading to increased load and pillar failure throughout the stope.

At some point, the roof may fail and cave to the surface, relieving the load on the remaining pillars or solid rock and effectively arresting the subsidence process.

In the case of an area supported by slender pillars that are surrounded by solid ground and larger pillars, failure of the small pillars would cause loads to be transferred to the larger adjacent pillars, which may be more capable of supporting the transferred load.

As in the previous case, roof failure and caving may occur and relieve loads on the remaining pillars.

This is believed to be the case in the Domado mine, where mine maps indicate that several small, slender pillars were present beneath the area of a large stope that ultimately collapsed. Larger, remnant pillars bound the northern and eastern edges of this collapsed area.

The potential for future pillar collapse and the domino effect of adjacent pillar collapses can be evaluated using various numerical and mine stability analysis methods.

Such methods, however, require some detailed information on the size, distribution, and condition of the pillars.

One of the major limitations to the subsidence analysis in the Picher Mining Field is the lack of confirmed information on the presence and condition of pillars.

It is believed that many pillars shown on existing mine maps may have been either removed or shaved.

In longwall coal mining the width-to-depth ratio of the mine opening is commonly used in combination with the extracted seam thickness to determine the potential magnitude of trough type subsidence.

The opening width-todepth ratio has also been used in hard rock mining as an indicator of subsidence potential over vertically extensive stopes.

In general, stope width provides an indication of the potential for mine roof failure, and stope height and depth provide a measure of the potential for a mine roof failure and subsequent caving to reach the ground surface.

In essence, wide and high openings at relatively shallow depths below the surface are more likely to result in subsidence than narrow and/or low openings at greater depths.

Extraction ratio is a measure of the volume or areal extent of ore extracted in a given stope relative to the premined volume or area of the stope.

For mine openings of rectangular cross section, the volume extraction ratio and the areal extraction ratio are the same.

An areal extraction ratio of 1.0 (100%) indicates that all the ore was extracted and no pillars were left.

An extraction ratio of 0.75 (75%) indicates that 25% of the mined area was left as pillars.

In general, measurements from mine maps in the study area indicate that areal extraction ratios in the Picher Mining Field exceed 0.90 (90%), with relatively small pillars located throughout a maze of interconnected workings.

Extraction ratio, however, is not a reliable single measure of either roof failure or subsidence potential, in that it is independent of the geometric factors (e.g., stope width, length, height and depth) that contribute to collapse and subsidence.

Nevertheless, once the critical width of a stope has been reached, the presence or absence of pillars will determine the stability of the immediate roof, and a lower extraction ratio will promote opening stability.

The depth to and height of an underground opening, in conjunction with the bulking characteristics of the overlying rock mass, will determine whether a void initiated by mine roof failure will eventually propagate to the surface.

In an abandoned mine, roof failure and subsequent upward caving of the overlying rock leads to the accumulation of a growing pile of broken, unconsolidated rock on the mine floor.

As the caving or chimneying progresses upward the pile grows, but because the broken rock occupies a larger volume than the intact rock the height of the pile on the mine floor grows faster than the thickness of mine roof that has failed.

As the caving or chimneying process continues, the void between the failing roof and rock pile will either fill and the process will be arrested, or it will continue until it breaks through to the surface as a chimney or plug subsidence.

The measure of the volume of broken rock to intact rock is called the “bulking factor”, and it varies for different types of rocks.

If the bulking factor for the rock is 1.4, failure of 10 feet of mine roof will result in approximately a 14-foot high pile of broken rock (some spreading of the caved rock laterally into the mine opening will likely occur)

Bulking factors of rock typically range between about 1.3 and 1.5 (Bell and Stacy, 1992; Whittaker and Reddish, 1993).

Weaker rocks such as shales have bulking factors on the low end of the range, and the stronger, more brittle rocks are on the higher end of the range.

In a study of subsidence above abandoned coal mines, the Colorado Mined Land Reclamation Division (CMLRD) has developed an equation for the probability of subsidence based on mine depth and void height (CMLRD, 1986).

For a probability of 1.0 of subsidence, the ratio of depth to mine floor to void height was 6.2 or less.

This ratio indicates a bulking factor of about 1.2 for the coal measure rocks overlying the mine workings.

Similarly, the Ohio Department of Transportation (ODOT) has developed a detailed site evaluation procedure for evaluating subsidence potential along transportation corridors located above abandoned coal mines (ODOT, 1998).

The ODOT procedure uses the ratio of minimum overburden thickness to maximum mined interval thickness as an indicator of chimney subsidence potential.

A ratio of overburden thickness to mined interval thickness of 5.0 is used by ODOT to represent the highest likelihood of subsidence, and corresponds to a bulking factor of 1.2.

The bulking factor of 1.2 based on the above CMLRD and ODOT experience is for coal measure rocks that are predominantly shales and sandstones.

However, different geologic materials will have different bulking factors, and it is possible that areas of the Picher Mining Field that contain a significant thickness of limestone bedrock in the immediate roof and overlying horizon will have a higher bulking factor (i.e., lower subsidence potential) than areas that are overlain by shale alone.

Various methods are available and have been used in the past to evaluate mine stability and subsidence potential.

Most of the methods are appropriate to site-specific studies and require relatively detailed geologic and rock property information to be effectively utilized.

As such, they are not readily applicable to evaluating subsidence potential over large areas such as required in this evaluation.

They may be applicable, however, in later, more detailed studies and geotechnical evaluations of specific locations identified as high risk for future subsidence.

A brief summary of some of these evaluation methods used in non-coal mines is presented below.

4.6.1 Crown Pillar Stability Analysis in Hard Rock Mines

The layer of rock that separates the roof of the shallowest underground opening in a hard rock mine from the ground surface is commonly referred to as a “crown pillar.”

Methods for analyzing crown pillar stability, and hence the potential for subsidence, have been developed using Rock Mass Quality (Barton, 1974) and Rock Mass Rating (Bieniawski, 1974) systems that were originally developed for and subject to more widespread use for rock tunnel stability analyses.

Along with RMR, the Mining Rock Mass Rating and Modified Stability Graph methods have been developed and tailored for use in stope stability analyses.

These methods, however, are intended for use in site-specific evaluations and require the use of detailed geologic and rock property data and information that is not currently available for the study area.

Roof stability analyses can be conducted assuming that the mine roof can be modeled as a plate or a beam.

These analyses utilize the stope width and stope length (plate analysis) or stope width (beam analysis), the thickness of the roof rock, and the mechanical properties of the roof rock (e.g., tensile and shear strength). The maximum stress in the plate or beam is inversely proportional to the beam or plate thickness.

In roof stability analysis the thickness of the roof rock is substituted for plate or beam thickness (Adler and Sun, 1976)

4.6.3 Rock Mass Rating, Mathews Stability Graph Methods for Stope Stability Analyses As with crown pillar analysis, standard stope stability analyses have utilized Rock Mass Rating, Mining Rock Mass Rating, Hangingwall Stability Rating, and most recently the Mathews Stability Graph (MSG) for stope design.

In these cases, designers seek to maximize the dimensions of an open stope prior to mining.

These methods require the use of detailed geotechnical data typically collected during mine exploration.

The detailed data required for reliable use of these methods is not available for mines in the Picher Mining Field.

Nevertheless, a general discussion of one of the most recently developed stope stability methods illustrates the parameters that are important to determining stope roof stability.

The MSG method, as reported by Mawdesley (2000), relates the Mathews Stability Number (N), a measure of the rock mass properties, stress, and opening orientation, to the hydraulic radius of the stope (area of the stope roof divided by the perimeter of the stope roof).

The hydraulic radius is a convenient one-parameter measure of the geometry of the underground stope. In this type of analysis the hydraulic radius is used as a geometric measure of stope instability.

Subsidence may be evaluated using numerical methods, such as finite element and finite difference techniques where there is sufficient and reliable mine geometry, geologic, and rock property data to provide required input into the numeric models.

Several types of software packages are commercially available, including Itasca’s FLAC model.

The FLAC model, as well as others, has been widely used in the mining industry for mine design and to evaluate mine stability and subsidence.

Numerical modeling is not considered to be applicable to the current study due to the lack of accurate, mine-specific rock property data.

However, it may be applicable to future, mine-specific subsidence evaluation in areas that have been identified as having a high likelihood of subsidence based on this study.

Factors considered in the selection of an appropriate subsidence prediction tool for use in the Picher Mining Field are the characteristics of existing ground-failure case studies; the data and information regarding ground conditions throughout the study area that would be available for use in the analysis; the goals and use of the analysis tool that was developed; and the available technology, models, and computer software.

The lateral extent of mines in the study area required the selection and use of a systematic, computer-based subsidence potential evaluation methodology.

The following criteria were thought to be essential in accomplishing the project’s goals:

• Ability to adapt the methodology for use with Mine Planning Software (MPS) or a Geographical Information System (GIS) so that systematic evaluation could be performed for the entire study area.

• Ability to predict the potential for chimney, or plug type subsidence to occur.

• Ability to estimate the potential magnitude of vertical subsidence if mine roof failure was to occur.

Consideration of the above factors and goals dictated that an empirical or semi-empirical approach be used for predicting the potential for subsidence in the study area.

In such an approach, data associated with prior collapses are collected, characterized, and catalogued, and then subjected to parametric analysis to determine the contribution and importance of each parameter relative to ground failure.

The rationale and methodology are then developed for the application of this information in forward analysis models to predict the location and likelihood of future subsidence.

Such an approach was utilized in this subsidence hazard evaluation.

Adler, L. and Sun, M. C., 1976, Ground Control in Bedded Formations, Bulletin 28, Research Division, Virginia Polytechnic Institute and State University, March, 1976.

Barton, N.R., Lien, R. and Lunde, J., 1974. Engineering Classification of Rock Masses for the Design of Tunnel Support. Rock Mechanics, Vol. 6., 1974.

Bell, F.G., and Stacey, R., 1992, Subsidence in Rock Masses, Ch. 13 in Engineering in Rock Masses, Butterworth- Heinemann.

Bienawski, Z.T., 1984. Rock Mechanics Design in Mining and Tunneling. Balkema, Rotterdam, 1984.

Brady, B. H. G., and Brown, E. T., 2004, Rock Mechanics for Underground Mining, published by Springer Geosciences, 3rd ed., 2004, XVIII, 626 p., Soft cover, ISBN: 1-4020-2064-3.

CMLRD, 1986, Boulder Weld Coal Field Evaluation, Prepared for the Colorado Mined Land Reclamation Division, 1986, Published by Colorado Geological Survey.

Keheley, E., 2005, Personal Communication.

Luza, K. V., 1986, Stability Problems Associated With Abandoned Underground Mines in the Picher Mining Field, Northeast Oklahoma, Oklahoma Geological Survey, Circular 88, 114 p.

Mawdesley, C., Trueman, R., and Whitman, W. J., 2000, Extending the Mathews Stability Graph for Open Stope Design. Transactions of the Institute of Mining and Metallurgy, v. 110, Jan–April, 2001.

Obert, L., and Duval, W.I., 1967, Rock Mechanics and the Design of Structures in Rock: New York, John Wiley & Sons, Inc., 650 p.

Ohio DOT, Geotechnical Division, 1998, Abandoned Underground Mine Inventory and Risk Assessment Manual, Prepared by Ohio Department of Transportation, Office of Materials Management, Geotechnical Design Section, May 15, 1998.

Tar Creek Five Year Review, 1994, U.S. Environmental Protection Agency.

Whittaker, B.N., and Reddish, D.J., 1993, Subsidence Behavior of Rock Structures, v. 4, Ch. 28 in Comprehensive Rock Engineering, Pergamon Press.

The Subsidence Evaluation Team identified three primary types of information that would be useful to land managers and convey the information on the extent, probability, and magnitude of mine subsidence that could affect the study area. These three types of information are:

• Mapping that indicates the location of mine workings and mine shafts.

• Mapping that indicates the potential maximum subsidence from mine workings, and,

• An analytical tool to evaluate the probability of subsidence for prioritizing sites.

The following portions of Section 6 discuss the methods that the Subsidence Evaluation Team used to develop this information within the Picher Mining Field.

Information available for the Picher Mining Field related to mine subsidence is generally limited to the mine mapping and geologic information discussed in previous sections of this report.

The lack of any detailed rock mechanics data for the study area and the need to use available information in any analysis limited subsidence-factor identification to the approach and factors described in the following subsections.

6.1.1 Purpose of Back-Analysis

The purpose of the back-analysis of large existing subsidence features resulting from mine collapse was to identify those factors or combinations of factors that are common to the existing subsidence features.

Variables associated with both collapse and non-collapse subsidence case studies were tabulated and analyzed statistically to determine those factors and/or combinations of factors that are associated with large subsidence features.

These critical factors were then used to evaluate the probability of similar future subsidence events in the study area that were not part of the case studies.

Early in the planning process, the Subsidence Evaluation Team determined that the empirical back-analysis approach outlined above offered the only viable method to determine the probability of subsidence in the study area.

The inventory of mine collapse features compiled by Luza (1986) was used to select a sample of typical collapse features throughout the Picher Mining Field.

The types of features selected for the back-analysis were typically the large, crater-like subsidence features because such subsidence represents the greatest danger to public safety.

These large subsidence features are also readily identifiable as resulting from underground mine collapses, whereas smaller subsidence features may be related to shaft failures or natural processes such as karst formation.

Luza (1986) distinguishes two types of subsidence features in the Picher Mining Field: shaft related and non-shaft related collapses (see Sections 2 and 4).

Shaft related collapses typically result from the failure of wooden cribbing in the upper portions of a shaft where it penetrates the shale, sandstone, and near-surface soils.

These weaker materials then collapse into the shaft, forming a circular collapse feature that typically enlarges with time due to erosion and further deterioration of the shaft opening.

Some of these shaft failures can become quite large over time (Luza, 1986).

The second type of subsidence identified by Luza (1986) results directly from the collapse of underground mine workings, and is referred to as non-shaft related collapse.

Most of the subsidence features in the Picher Mining Field are shaft related collapses (Luza, 1986).

Although shaft related collapses represent a significant hazard in the Picher area, the back-analysis focused only on non-shaft related collapses.

This is because the mechanisms involved in the two different types of subsidence are entirely different.

Also, the extensive inventory of mine shaft locations in the Picher Mining Field (Luza, 1986; Keheley and Pritchard in Oklahoma Governor Frank Keating’s Tar Creek Superfund Task Force Final Report, 2000) provides information on the locations of these potential hazards, and the area of potential hazard from a shaft collapse can be easily defined.

Locations of non-shaft collapse features, on the other hand, are much more difficult to identify and are dependent on a wider range of factors than shaft related collapses. Thus, the back-analysis was concerned only with non-shaft related collapses.

However, as will be discussed later, the presence or absence of shafts was a factor considered in the back-analysis of the non-shaft related collapse.

In order to determine the factors that contribute most to large subsidence features in the Picher Mining Field, it was necessary to also include areas of no subsidence in the statistical analysis.

Therefore, areas of mine workings similar to and near those that produced subsidence features were also selected for inclusion in the case studies.

During initial planning meetings to develop the strategy for conducting the hazard assessment, the Subsidence Evaluation Team collectively developed an initial list of variables that were thought possibly to contribute to mine collapse and ultimately, subsidence.

A subgroup of the Subsidence Evaluation Team, the Back-Analysis Subgroup, was later formed to refine this list of variables and to select the case study areas.

The Back-Analysis Subgroup also interpreted mine maps, drill logs, and other sources of information in order to determine and tabulate the values for the selected variables for each case study.

The Back-Analysis Subgroup used existing mining and rock mechanics literature, and the personal experience of members, to select a set of variables that were suspected of contributing in some way to the occurrence of subsidence.

These variables were included in a statistical analysis that ultimately led to the identification of a selected set of variables that are highly correlated with subsidence.

A brief explanation of each variable and why it was considered important in the back-analysis is provided.

Some of the variables have numeric values, while others have simple “yes” or “no” values, depending on the presence or absence of a characteristic.

Number of mine levels present:

Intuitively, the likelihood of mine collapse would be expected to increase where multiple-level mining took place.

Not only is there greater opportunity for mine-roof failure with multiple levels due to reduced roof thickness at each level and the possibility of staggered pillars (as opposed to being stacked above one another), but the total volume of material removed by mining would be greater than if only single-level mining occurred, thus increasing the probability of subsidence should collapse of the underground workings occur.

Number of shafts within the stope or collapse area:

Although back-analysis focused only on non-shaft related collapses, the presence of shafts within a specific stope or mining area was suspected to contribute to weakening of the mine roof. Thus, the presence of shafts within a stope area could possibly be a factor in the collapse of the underground workings, even if the upper portions of the shaft did not fail in the typical fashion.

Rock falls noted on maps:

The presence of rock falls within the mine workings during mining is an indication of unfavorable mine-roof conditions.

The team suspected that such locations are areas of possible future mine collapse and subsequent subsidence.

Pillars removed or trimmed:

The trimming or removal of pillars results in the loss of support for the mine roof and increases the likelihood of collapse of the underground workings.

Unfortunately, as discussed below, much of the pillar removal or trimming in the Picher Mining Field was done by gougers after the primary mining phase was completed; records of pillar removal are either absent or incomplete.

The Back-Analysis Subgroup suspected that where pillars had been trimmed subsequent to the primary mining operations, there was a greater likelihood of instability due to inadequate support.

Chat pile over all or part of stope:

The presence of chat piles on the surface above the mine workings results in additional load on the mine roof and pillars that was not considered by mining engineers when the mines were originally worked.

The Back-Analysis Subgroup suspected that the existence of these chat piles could be a contributing factor to mine collapse.

Width of stope:

The Back-Analysis Subgroup suspected that the greater the width of stope or mine opening, the greater the likelihood of roof failure and mine collapse.

Length of stope:

Although it is generally recognized that the width, rather than the length, of a stope or mine opening is more likely to impact stability, the Back-Analysis Subgroup suspected longer openings afford an increased chance of encountering weaknesses in the mine roof, and thus could also be a contributing factor to mine collapse.

Maximum unsupported span:

The greater the unsupported span within an underground opening, the greater the stress on the roof and pillars, and the more likely roof failure and mine collapse will occur.

Height of stope:

Although the height of the stope is generally not a controlling factor in mine stability, it is a potential factor in mine subsidence.

The greater the stope height relative to the thickness of overburden, the more likely that surface deformation (subsidence) will occur in the event the mine opening collapses.

Depth to top of stope:

The closer the mine workings are to the surface, the more likely that mine collapse will result in subsidence.

This is because there is less material above the mine opening to fail and bulk (expand) to fill the opening, thereby stopping upward stoping.

Interburden thickness between mine levels:

Interburden is defined as the intact rock between adjacent mine levels.

It is generally believed that thin interburden between two levels is more likely to fail than thick interburden.

In addition, the Back-Analysis Subgroup suspected that failure of the interburden would effectively result in greater stope height, as two or more mining levels would combine into a single larger opening.

Areal extraction ratio:

Areal extraction ratio is the ratio of the excavated area to the total area of a mine or stope.

The greater the areal extraction ratio, the greater the amount of material removed by mining and, less material available to hold up the mine roof.

In addition, higher removal rates result in more space to be filled by the overlying rubble as the mine collapses.

For mine openings that are rectangular in cross-section, as is approximately the case for most mines in the Picher Mining Field, the areal extraction ratio is the same as the volume extraction ratio, which is defined as the ratio of the excavated-to-total volume of a mineral deposit or portion of a mine.

Areal extraction ratio is easily determined from the mine maps.

The Back-Analysis Subgroup suspected that a greater extraction ratio would result in greater likelihood of subsidence.

Ratio of height of stope to thickness of overburden:

This is a calculated value from two of the previous variables.

As noted above, the height of stope is not necessarily a critical factor in determining stope stability, but the height of stope relative to its depth below the surface is a factor in determining if mine collapse will propagate to the surface and produce a subsidence feature.

Thickness of Boone Formation above stope:

The Boone Formation, in which most of the ore within the Picher Mining Field was mined, is a relatively strong and competent rock compared to the Chester and the shale units that overlie the Boone Formation.

Therefore, the Back-Analysis Subgroup suspected that the thicker the overlying Boone Formation above the mine opening, the stronger the mine-roof and the more stable the opening.

Thickness of Chester above the stope:

The Chester is a collection of less competent limestone and interbedded sandstones and shales, and is generally weaker than the underlying Boone Formation.

The thickness of the Chester above the stope was therefore considered to be a possible factor in mine collapse and subsidence.

Thickness of alluvium and shale above the stope:

The shale and alluvium that overlie the Chester are relatively weak and incompetent.

As such they have little ability to provide roof support and may actually behave more as dead load on the underlying, more competent materials above the mine opening.

Therefore, the Back-Analysis Subgroup suspected that the greater the thickness of shale and alluvium over the mine openings, the greater the potential instability of the openings.

Mapped tectonic/geologic features within or near the collapse or stope area:

The presence of geologic features such as folds, faults, or fracturing may be a factor in mine collapse in that they represent weaknesses in the rocks that could degrade opening stability.

Geologic factors considered in the back-analysis were the presence of faults, folds, or fracturing noted on mine maps and reports; proximity to the Miami Trough (within 1 mile); and the presence of karst structures.

The Back-Analysis Subgroup believed that the presence of such features inside the footprint of a mine might lead to decreased strength and increased subsidence.

As noted earlier, the inventory of subsidence features in the Picher Mining Field (Luza, 1986) was used to select most of the back-analysis case studies.

Several moderate to major subsidence features, identified by Luza (1986, Plate 2) as deeper than 30 feet and greater than 95 feet in diameter, were chosen for back-analysis.

Criteria used to select the case studies included that

1) the subsidence feature be non-shaft related,

2) there be one or more exploratory drill holes in the area to provide subsurface geologic information,

and 3) mine maps were available to define the extent and geometry of the mined area.

For these reasons, not all of the moderate to major subsidence features inventoried by Luza (1986) could be included in the case studies.

One small subsidence feature that occurred after the 1986 Luza inventory (case study #28, Scammon Hill Mine) was included in the case studies in order to incorporate a sampling of more recent collapses.

Case study #7 (Ritz Mine) had also not been previously identified as a subsidence feature. During the course of this study, the question arose as to whether the pond at this location was the result of subsidence.

Further field examination, including a depth profile of the pond by U.S. Army Corps staff, indicated that it likely was the result of mine collapse and was not a mill pond as previously thought.

This location was therefore added to the back-analysis as a collapse case study.

The intent in selecting the back-analysis case studies was to produce a representative sampling of the larger, nonshaft related collapses over the entire Picher Mining Field so as to include a range of geologic conditions present within the field.

Ultimately, a total of twelve subsidence features were selected for the back-analysis.

In addition, a total of 17 non-subsidence examples were selected from the detailed mine maps.

In most cases, the non-subsidence examples were taken from areas of the mine near where the subsidence occurred.

In selecting the mine locations to represent non-subsidence cases, large stope areas similar to the collapsed stope were chosen.

The locations of the subsidence and non-subsidence case studies within the Picher Mining Field are shown in Figure 6.1. Figures Da through De in Appendix D show the location of the case studies at the scale of the individual mine lease in which they occur.

These figures also show the width and length axes that were used to characterize the dimensions of the individual stopes, and thus provide some insight into the rationale used in deciding the stope boundaries.

A brief description of each case study is presented in Appendix D, along with a separate figure showing the detailed mine map in the area of the case study superimposed on 2004 aerial photography.

The detailed figures also show the location and length of the axes used to define the stope dimensions as determined from interpretation of the detailed mine maps.

Drill logs used in determining the thickness of geologic units at each site, and in some cases the elevations of the mine roof from assay data, are also included in Appendix D. Geologic contacts were picked from the drill logs using the same criteria applied in interpreting the logs to develop the Conceptual Site Model of the region, as described in Section 5.2.

The empirical back-analysis approach used to develop the GIS screening criteria in this subsidence hazard assessment is intended to be applicable to the study area, and ultimately to the entire Picher Mining Field.

Several factors may contribute to mine collapse and subsidence at any particular location, and the factors or combination of factors may not be the same in all cases.

The back-analysis was therefore intended to develop a representative sample of variables possibly associated with mine collapse from the entire region, from which critical factors can be identified that may be used to estimate the probability of a major subsidence within the study area.

One of the major limitations to this approach is that all but one of the subsidence cases selected for back-analysis are major subsidence features, with horizontal dimensions on the order of 100 feet or more and vertical deformation of several tens of feet.

As noted earlier, these larger features were selected because they represent the greatest potential threat to public safety, and almost certainly result from the collapse of large underground rooms, or stopes.

Smaller subsidence features that occur in the Picher Mining Field are less easily identified and can result from processes other than mine collapse, such as shaft cribbing failure and dissolution of limestone resulting in karstic features.

Trough subsidence, characterized by shallow subsidence over relatively large areas, was also not included in this analysis.

Trough subsidence, while possibly present in the Picher Mining Field, is not easily identifiable and has not been well defined in the region. The screening criteria that result from the back-analysis are, therefore, only applicable in identifying potential areas of large surface deformation.

The reliability of the information used to quantify the variables for the back-analysis is also influenced by a number of factors, including the age and quality of the mine maps, the complexity of the maps, the subjectivity involved in selecting stope boundaries, and the complexities introduced by multiple-level mining.

One of the biggest uncertainties arises from the question of pillar robbing and gouging activities that took place after the primary mining phase, and were thus not documented on the maps.

Removal of pillars and/or enlargement of stopes by gouging would be a major contributing factor to mine collapse, but unfortunately, the areas where such activities occurred are poorly documented.

The mine maps used to determine stope dimensions were produced between 1945 and 1967.

Most of the maps were produced between 1955 and 1965, and are thus considered relatively reliable with respect to final mine configurations.

One or two possible case study sites were discarded early in the investigation because maps of those mines dated later than the 1930s could not be found.

The complexity of the mine maps also contributed to uncertainty in their interpretation.

Complexity was mainly introduced where multiple-level mining was practiced.

The various levels were portrayed on the maps with different types of lines, such as solid lines for the main level (generally called the “M” level) of mining, and variations of dashed and dotted lines for the upper and, in some cases, lower levels of mining.

Where three or more levels of mining were present at the same location, it was often difficult to determine the final three-dimensional configuration of the workings.

Also, mine floor and roof elevation data were often not displayed in sufficient quantity on the maps to allow the height of the openings to be determined.

Oftentimes, two or more levels of mining combined to form one large stope.

To make matters more difficult, it appeared that the convention of which type of line represented which level was not always consistent from mine lease to mine lease, and in some instances varied on the map of a single lease.

This made it very difficult in some cases to determine the limits of individual stopes with a high degree of confidence.

In many cases, subjective judgment was also involved in selecting the stope boundaries.

In some cases, the shape and lateral extent of stopes were obvious and could be well defined from the mine maps.

In other cases, the irregular shape of the mined area, the varying density of pillars, and the lateral extent of mining in one or more directions suggest that a well-defined stope was not present.

In such instances, the selection of dimensions to represent the stope was somewhat subjective.

In several cases, the mine maps did not provide sufficient information on floor and roof elevations to reliably determine stope heights.

In these cases, mine assay data from logs of nearby exploratory borings were used to infer stope heights.

In several instances where both mine-map elevation data and borehole logs were available, a comparison between stope heights from the mine maps and those inferred from the assay data were in close agreement.

The use of assay data to infer stope heights was thus considered to provide reasonable stope height estimates where mine map data were lacking.

The presence of multiple-level mining in some of the case study areas also presented a problem from the standpoint of the back-analysis.

Where subsidence occurs over a single level of mining, it is obvious that the subsidence resulted from collapse of the underlying stope.

Where multiple-level mining occurred, it was not apparent at which level the mine collapse may have initiated, and therefore unclear which stope dimensions and properties to include in the analysis.

From a rock mechanics standpoint, however, the stability of the mine roof is primarily dependent on the width of the opening, the unsupported span, and rock strength properties, not on the height of the opening.

Thus, the collapse of a lower level or levels to form a combined opening would not necessarily result in surface deformation.

Subsidence will only occur if there is failure of the roof of the uppermost level, or crown pillar.

Failure within the lower mine levels could ultimately result in failure of the crown pillar through effective widening of the underlying opening.

However, because it is not possible to know where failure initiated in multiple-level collapses, it was assumed that mine collapse initiated in the highest level of mining.

Therefore, the stope dimensions and properties tabulated in the back-analysis for multiple-level mining cases are for the uppermost stope.

Another source of uncertainty in the tabulated variables is in the interpretation of the exploratory drill logs to derive the geologic contacts, and thus determine the thickness of the overlying geologic units used in the back-analysis.

Drillers, rather than trained geologists, compiled drill logs, and the common use of non-geologic terminology contributed some uncertainty in determining geologic contacts.

All of the variables determined for the 12 subsidence features and 17 unsubsided case studies are presented in Tables 6.1A and 6.1B.

Also included in the table is accessory information regarding the date or approximate date of the subsidence, the drill logs used to derive the geologic and stope data for each case study, the mine maps used to determine stope dimensions, the size of the surface collapse where applicable, and any additional comments.

The case study number is presented in column 1, followed by the mining lease name in column 2. The case studies are organized by lease, and are designated as subsided or unsubsided cases in column 3.

Except as noted below, the data contained in Table 6.1A were subjected to multi-variant statistical analysis in order to identify those factors that are most commonly associated with the large surface collapses.

These critical factors, once identified, were formulated into a logistic regression equation.

Target areas within the study area having the potential for subsidence should complete collapse of the underground workings occur were identified using a GIS model.

The logistic regression equation was then used to estimate the probability of subsidence of these target areas.

Target areas where the critical factors are present are thus identified as areas of relatively high subsidence hazard.

It is noted that case study #28 (Scammon Hill Mine) was not included in the final statistical analysis to determine key subsidence factors.

This particular case study is a small surface collapse compared to the other case studies;

although the mine workings under the subsidence feature are relatively high, they are narrow and occur at greater depth than all but one of the other case studies.

Because of the mine geometry and depth, this case study did not fit the statistical trend suggested by the other surface collapse cases.

The presence of mine shafts near the subsidence feature and the existence of underground caves noted in descriptions of this mining area raised concerns that the subsidence might have been caused by processes other than mine collapse.

The small size of the subsidence feature, and the uncertainty that it resulted from the same processes as the other collapse case studies, lead to the decision to exclude it from the statistical back-analysis.

Although not included in the final statistical results, case study #28 has been retained in Tables 6.1A and 6.1B.

A statistical analysis of the variables determined from the 12 subsidence features and 17 unsubsided case studies was performed to identify those factors that are most commonly associated with large surface collapses observed within the study area.

The primary objectives of the statistical analysis were to identify those variables that are most highly correlated with large surface collapses, and to evaluate the relationships between these variables.

These statistical relationships were used to quantify the probability of large surface collapses occurring in areas not evaluated as part of the back-analysis.

A broad class of statistical methods is available to evaluate the relationship between an independent variable, referred to here as a predictor variable, and a dependent variable called an outcome.

This class of methods, called generalized linear methods, includes ordinary regression and analysis of variance (ANOVA), as well as multivariate statistics such as analysis of covariance (ANCOVA) and log-linear regression (Agresti, 1996; Menard, 1995).

One of these methods, logistic regression, is unique in that it allows prediction of a dichotomous or binary outcome from a set of variables that may be continuous, dichotomous, or categorical.

Continuous variables are those that can have a range or continuum of values.

For this study, continuous variables include measured values such as depth to mine stope or thickness of geologic units.

Dichotomous variables are binary in nature and usually describe the presence or absence of a feature.

In this study, examples of dichotomous variables could include the presence or absence of rockfalls, pillars, chat piles, and tectonic features.

Logistic regression is also unique in that the probability of a particular outcome can be estimated as a function of the values of the independent model variables.

In the present study, the dependent variable is the state of the surface above the mine workings, either subsided or unsubsided.

Because the selected mine subsidence variables described in Section 6.1.2.1 include both continuous and dichotomous variables, and the desired outcome is binary in nature, logistic regression analysis was selected as the appropriate statistical model for the subsidence evaluation.

Case History Number: 1
Mine Lease Name: Woodchuck
Subsided or Unsubsided: subsided
Approx Date of Collapse: pre-1939
Drill Logs: #19c, #21c
Mine Map Used: oi sene 30-29-23 140 1945 Woodchuck O-21 bw 1-1 okspn83usft.tif
Mine Map Date: 8-24-45
Comments: 165 ft circular surface collapse, pre-1939. Upper mine level collapse.Stable since 1952. #35 on Plate 2,Circular 88. Two levels mined in area, but only upper level mined in area of collapse.

Count: 1
ID: 0
Northing:724,251
Easting:2,894,732
Quarter, Quarter Section:NW
Quarter Section:SW
Section: 33
Mine Lease:John Hunt
Estimated Maximum Subsidence (feet):10-25
Maximim Probability of Subsidence:< 20
Estimated Area (ac):0.172
Affected Features:East of Hwy 69 in field

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THE MINING PROCESS IN THE TAR CREEK SUPERFUND SITE

It is important to take a look at the history of the mining process that was practiced in the Superfund Site to understand why the subsidence problem has developed.

The type of mining conducted in the Tar Creek Superfund site was commonly referred to as random room and pillar mining.

The rooms were excavated and pillars were left to support the mine roof.

The mining procedure in the Picher Mining Field differed markedly from that in other parts of the United States due to the hit-or-miss, non-uniform ore appearance and the numerous companies that were a part of the mining business.

The US Army Corps of Engineers’ Subsidence Evaluation Team for the Tar Creek Superfund site provided an example of the most frequent sequence of mine events in the Tar Creek area as follows:

1. Thorough inspection and laboratory analysis to pinpoint the location and quality of ore within a given land boundary.

2. Constructing milling facilities and shafts to access the ore body.

3. Primary mining of rooms while moving away from the shafts to find and remove high-grade ore.

The underground superintendent, or Ground Boss, guided the mining process to the point that pillar locations and sizes depended upon the boss’s personal experience rather than pre-approved design.

4. As mines became depleted of ore, the mining companies conducted pillar trimming or complete pillar removal.

Remaining mine workings were often sub-leased to independent miners, known as “gougers.”

These miners removed remaining ore from the roof, walls, pillars & floors.

The mine worker's (Roof Trimmer) would atop a 70-foot extension ladder used a metal bar to remove loose debris from the roof.

The Roof Trimmer was the highest paid employee in the underground mines.

To Top of Section Photo source: Picher Mining Field, NE OK Subsidence Evaluation Report for US Army Corps of Engineers

A description of mining at its most dangerous, known as “ladder mining” follows:

"…Roof trimming ladders are made of selected spruce in 20-ft sections.

' When a 5-section ladder is run out, four guy ropes equally spaced with two men to a rope are used to steady the ladder and tilt it carefully back and forth to cover a little more area.” (Eagle-Picher,1943)

Examples of Subsidence An account of how thoroughly gougers removed mine materials follows:

On Saturday morning July 22, 1967 an area 250-by-300-feet collapsed on the northwest side of Picher in the Netta White mine within eight hours of pillars being removed by gougers.

The surface near the center of the collapse dropped approximately 25 feet.

Four homes containing 18 persons were involved in the 1.5 acre collapse.

Fortunately, the collapse occurred slowly and no serious injuries occurred

Picher Mining Field, NE OK Subsidence Evaluation Report for US Army Corps of Engineers

THE OBSERVATION METHOD

The Observational Method essentially permits the development and use of a simple model to represent a complex process with subsequent observations of the process results, updating and refinement of the model based on the observed performance, and continued use of the model to predict process performance and manage the problem at hand.

The empirical methodology used for subsidence potential evaluation in this study is based on an analysis of actual mine subsidence events using data and information derived from archived mine maps and drill-hole data retrieved from pre-mining exploration logs.

While the derived model is believed to be conservative (i.e., it is expected to over predict subsidence potential), its actual performance has not yet been confirmed. The observational method would therefore be focused on validating the empirical approach along with refining both the model and approach as indicated.

Physical observation, exploration and instrumentation would be the primary observational method tools that can be applied in the Picher Mining Field. Continuing expansion of the case-study data set and further proofing and analysis of the overall case-study data set may also be appropriate.

ADAPTIVE MANAGEMENT

In general, adaptive management is an iterative, learning-oriented methodology for managing complex systems that are characterized by high levels of uncertainty.

It is an iterative (cyclical) process of adapting management solutions to complex problems based on applying assumptions followed by observation and then re-applying new assumptions based on those observations to achieve a better management solution to the problem.

Adaptive management is well suited to be used in conjunction with the observational method and implemented for the Picher Mining Field project for the following reasons:

• The Picher Mining Field area is part of a complex system.

• The Picher Mining Field area is constantly changing.

• Land uses may change and evolve. For example, undeveloped land may be developed by commercial or private parties. This would change the associated potential effect if underground workings were to potentially subside in the area.

• Immediate action is required because of potential severe consequences to people living in the area currently and in the near future.

• There is uncertainty in the data set used to evaluate the Picher Mining Field system.

Although there is a large amount of historical data associated with the mining activities that have occurred, there is much information that has been lost or destroyed.

In addition, the physical and engineering properties of the soil and rock in the study area have not been characterized with respect to subsidence.

• The management system for the Picher Mining Field must be adaptable to new data, policies, land uses, and other factors.

INSTRUMENTATION OPTIONS

Instrumentation may be used to collect real-time data for early warning of potential subsidence.

Options for Detecting Migrating Voids

Subsurface void migration is routinely monitored using several techniques that can be adapted for continuous, remote monitoring with results immediately available via the Internet.

The following are two of the options:

Time Domain Reflectometry (TDR): Either standard TDR, using a coaxial cable, or optical TDR, using a fiber optic cable, can be used to measure propagation of roof failure toward the land surface.

In either case, the cable is grouted in a borehole drilled vertically from the surface into the mine void.

The surface-based hardware automatically measures the length of intact cable indicating a change when the roof failure breaks off the lower end of the grouted cable.

Multiple Point Borehole Extensometers (MPBX): MPBX are installed in boreholes drilled vertically from the ground surface to monitor strata displacements at predetermined horizons.

Anchor points can be established just above the existing mine roof and at up to five additional locations in the same borehole to progressively monitor displacements.

Data can be automatically recorded and transmitted via the Internet to a multitude of authorized users. Displacements accurate to 1/100 of an inch can be measured.

OPTIONS FOR SUBSIDENCE DETECTION & MEASUREMENT

The objective of this instrumentation is to detect the early ground movements that precede subsidence.

Several manual and automatic techniques are available. Two of them are:

Precise Leveling Surveys: Classic subsidence monitoring programs utilize land-based survey (i.e., precise leveling) techniques to precisely measure the magnitude of subsidence at predetermined locations throughout a project site.

LIDAR: LIDAR (Light Detection and Ranging)is an aerial survey method that provides an accurate means of collecting topographic information that is not affected by tree canopy.

Approximately 60% of the area was flown (aerial LIDAR) during 2004, with the remainder completed in early 2005.

Tripod-based LIDAR has also most recently been used at the subsidence site over the Skelton Mine at the southern end of Highway 69 as it traverses the study area.

OPTIONS FOR MINE GEOMETRY CHARACTERIZATION

Although there are mine maps of the workings for many mine sites, these maps may not always be complete or accurate.

Some of the mine sites do not have any mapping information, and other maps have been found to have conflicting information; there is the potential that caving after the termination of mining may have impacted the mine workings geometry.

Methods for better defining the extent of mine workings and their effect on the surface are described in the following subsections.

GEOGRAPHYSICAL METHODS

Geophysical methods such as ground-penetrating radar, seismic reflection or refraction, micro-gravity variation, magnetic, resistivity, spectral analysis of seismic surface waves, and nuclear resonance, have all been tried for use in locating and characterizing mine voids.

These techniques have often been proposed as less expensive alternatives to exploratory drilling for characterization of geological conditions in mining areas.

While some of these methods have been useful for the extrapolation of data between exploratory drill holes, the state reclamation program has District. These technologies may have important applications for the detection of eminent subsidence resulting from the migration of mine voids to shallow depths at the Tar Creek site.

INFRARED PHOTOGRAPHY

Infrared spectrometry provides the capability of photographing images in the infrared light spectrum, thereby capturing the thermal gradient of the images being photographed.

Discussions with the USGS in Denver, Colorado and the Jet Propulsion Laboratory (JPL) in Pasadena, California indicate that new technologies have been developed that provide greater capability for infrared imaging.

It may be possible to use infrared imaging to identify open mine shafts that are concealed by brush and other debris and to identify undetected, abandoned mine workings near the ground surface.

USGS staff indicate that a low-level flight (~12,000 feet) using infrared imaging provides sufficient resolution to identify openings such as mine shafts.

USGS staff indicates that the best time for such flights is following a rain shower where there is a difference in the evaporation rate from ground surfaces.

Infrared imaging utilized in conjunction with accurate mine maps may provide an addition tool to identify mine shafts as well as mine workings that have the potential for subsidence.

The use of infrared technology to update current conditions in the Picher Mining Field should be given consideration.

EXPLORATORY DRILLING

Exploratory drilling can provide the most accurate picture of the geological setting and the physical structure of mine workings.

Exploratory boreholes should be considered for making hole-to-hole or hole-to-surface seismic tomographic measurements in order to determine cavity shape and geologic boundaries.

However drilling is very costly to characterize a large area.

Typically, costs range from $7/foot for rotary drilling to $35/foot for core drilling.

Drilling is also very time-consuming and invasive to the community. Drillholes would provide an accurate vertical lithologic log of the area of concern.

Coupled with mine maps, existing drill logs, and GIS, drilling would be a very effective method for determining the size and condition of underground mine workings.

Although expensive, drilling remains one of the most reliable methods for characterizing underground mines for subsidence prevention and abatement.

HAZARD MITIGATION OPTIONS

In 1983 and 1986, the U.S. Bureau of Mines, in cooperation with state geological surveys issued reports on stability problems and hazard evaluations in the Oklahoma, Missouri, and Kansas portions of the Tri-State District (Luza, 1986).

Among other things, these reports identified five methods of hazard abatement for mine subsidence: backfilling, grading to gentle slopes, fencing, controlled collapse with explosives, and public education were all suggested.

Around the nation, other methods have also been used for abating hazards associated with subsidence.

These methods are discussed below.

FENCING OPTIONS

Fencing has been used in the Tri-State Mining Area for many years to keep people out of subsidence areas.

Fencing is intended to deter public contact and exposure to the mine problem, not to fix or stabilize it.

The 1983 Bureau of Mines study of problems in the Kansas portion of the Tri-State Mining Area suggests that, where mines are in urban areas or near roads, six-foot-high cyclone fencing be installed with barbed wire canted out at the top.

A major problem with theft exists with fencing.

Chain-link fencing, which has been installed in more remote areas, is often stolen within a few weeks of installation.

The BIA is currently considering using a stronger type of fencing that is less prone to theft.

Chain-link fencing used in public areas, such as downtown Picher, OK, survived for years without major damage or theft.

Fences would allow authorized access. Warning signs would be used to deter unauthorized entry.

Fences should be set back far enough from shafts so that they are not undercut by future caving of the shaft.

Fences are visible today surrounding mine subsidence pits and mine shafts in the Tri-State Mining Area.

Many of these are damaged or partially undercut by water or advanced subsidence or have weathered away.

Fences may be the most cost-effective method of protecting the public from the dangers of subsidence pits in many situations, but they must be erected with a plan for long-term maintenance and monitoring.

It must also be acknowledged that fences will not keep out determined explorers who wish to enter the subsidence pit area for mineral hunting, fishing, or other water-related activities.

The costs of fencing are dependent on local prices and on economies of scale.

BACKFILLING OPTIONS

Backfilling generally consists of placing material within the underground cavity to fill the open space and reduce the cavity size.

There are several different types of backfilling methods that are discussed below.

It is important to note that all backfilling techniques are very expensive and are unlikely to prove practical in the study area.

However, backfilling may be cost effective in certain situations within the study area.

• Hydraulic Flushing is the filling of mine voids with granular materials transported in a waterbased slurry.

Material placement is controlled by use of grout curtains or aggregate bulkheads constructed remotely from the surface through drill holes.

When mines are open and unobstructed, this method can result in up to 100% of void fill, effectively eliminating the potential for subsidence.

Complete fill is verified either by personnel working in the mine or by drilling confirmation holes from the surface after completion of work to determine if roof contact has been made.

This method has been used in Wyoming and other states to backfill coal mines under entire subdivisions.

However, the process requires large volumes of material and water.

• Grouting is the process of placing a mixture of cementitious material and fine aggregate as a fill material into the mine void.

The grout is typically placed at a low volume rate. Many states and the Office of Surface Mining (OSM) use gravity grouting to stabilize coal mines that begin to subside under homes, other buildings, and roads.

This is often a cost-effective method of ground stabilization where mine voids are not too tall (less than 8 feet) and the area to be stabilized is limited to structures or roads.

However, it can be used in mine voids of nearly any size and configuration.

The cost of grouting may become a problem for larger mine areas.

Three types of grouting are discussed below: - Gravity Grouting consists of placing a mixture of cementing agent (generally Portland cement) and fine aggregate into the mine level by means of a borehole. The most commonly used combination for mine grouting in the Midwest is a mixture of sand, Portland cement, and Type-F fly ash. The gravity head is the driving force used to place the grout. This is used frequently for abatement of subsidence under roads and structures associated with abandoned coal mine sites in Kansas and Missouri, and would be effective in certain situations in the Tri-State District.

- Pressure Grouting is the process of pumping the grout mix into the mine area and overburden at pressures ranging from one-half to one psi per foot of thickness of overburden.

Packers are used to seal the borehole so that pressure can be exerted on the grout.

This is used frequently for abatement of subsidence under roads and structures associated with abandoned coal mine sites and would be effective in certain situations in the Tri-State District.

Pressure grouting enables the operator to force grout into fractured and rubble zones, providing enhanced protection from subsidence.

- Compaction Grouting is the injection of a stiff (low slump) grout at high pressure, up to 500 psi.

The grout forms a ball at the point of injection and compacts the surrounding material.

This method is used to stiffen foundation soils that have lost strength and bulk due to subsidence.

It is also used to compact unstable fill in old mine shafts that were filled with trash or poorly backfilled in the past.

It is cost-effective for poorly filled mine shafts and structure-size stabilization projects but is not suited for area-wide projects.

• Grout Bags are heavy fabric bags that are filled with grout and designed to be placed through a borehole and into the mine workings to build artificial mine pillars.

As the bags fill, they form a column in the mine void to add additional support to the mine roof, reducing the potential for subsidence.

They have been used successfully in Pennsylvania where abandoned coal mine roof heights can reach 16 feet.

Staff from Hayward Baker, Inc. speculated that grout bags may be effective in mine rooms up to 30 feet tall (Kansas Department of Transportation [KDOT] Abandoned Mines Workshop, April 27, 2000).

It is understood that grout bags were being considered for use in 2000 by KDOT for stabilization of a road along the state line between Picher, OK and Baxter Springs, KS.

This method may also be used to construct underground barrier walls to contain pumped grout or hydraulic backfill materials.

GROUND SURFACE REINFORCING OPTIONS

Ground surface reinforcement is typically applied to areas where relatively small, localized subsidence is anticipated and is not generally suited to areas where large (e.g., > 20 feet) subsidence features are anticipated.

Geotextile Materials such as high-strength webs and nets have been used to reduce the effects of ground failure under roads.

KDOT has previously considered using this method to stabilize a road on the state line between Pitcher, OK and Baxter Springs, KS.

The method has also been used to seal abandoned coal mine shafts beneath a landfill expansion in Colorado.

The method involves excavation of the soil material under the area to be protected to a depth several feet below final grade.

The geotextile is unrolled and anchored along the edges, then backfill materials are placed over the material and compacted.

It has been suggested, in some cases, that the ground be excavated to a solid geologic formation and the geotextile deep-anchored to increase stability.

Dynamic Compaction is a process for compacting soils at depth.

The process involves dropping a weight in excess of 10 tons on a grid pattern from a given height.

This method is sometimes used for highway work and may have application for stabilizing abandoned exploratory holes dug by early miners.

The method has the potential to induce subsidence in areas where mine-roof structure has deteriorated substantially, so thorough knowledge of geologic conditions is important when planning its implementation.

The Missouri Department of Transportation is currently considering the use of dynamic compaction for the Range Line Road project at Joplin, Missouri.

Caissons, Grade Beams, Soil Nails, Driven Piers, and Rock Anchors are all methods that may be used to stabilize structures built over subsidence-prone areas.

They may reduce the danger of building damage and the cost of repairs after minor subsidence events occur.

However, these do little to stabilize the ground and do not stop or slow the progress of subsidence events.

RELOCATION OPTION

Relocation has been used in a few situations across the country where no other alternative existed to protect the public from extremely dangerous situations.

Relocation does not alleviate the problem, but it does remove the people from direct, daily access to it.

Relocation or buy-out in the study area could be used where the subsidence probability is high and where a costbenefit analysis shows it to be the most cost-effective approach to protecting the residents.

Relocation or buy-out could occur within or outside the study area and would likely be voluntary unless a government agency condemns the property.

Voluntary relocation or buy-out has several inherent problems.

It can have a net result of dividing a community.

It can also result in “off-limits” areas in communities where no development or activity can occur.

This tends to bring down nearby property values and reduce the tax base of the area.

For a variety of reasons, property values in the study area are significantly depressed, and the tax base has declined as a result of most businesses moving to other areas.

In 2002, the federal relocation costs for the Tar Creek Site were estimated to be between $49,000 and $118,000 per home.

A voluntary buy-out initiated by Oklahoma Governor Brad Henry in the spring of 2005 resulted in 60 families with children under six years of age being bought out in Picher, Cardin and Hockerville at an average cost of $51,000 per family.

This resulted in over 90% of the eligible families participating in the buy-out.

As a result of the buy out, the 2005 school enrollment for Picher-Cardin schools is down 25%.

It is recognized that in many instances, public participation is often not complete or enthusiastic. All relocation/buyout options have pros and cons.

Multiple public surveys taken in the Picher-Cardin area since 2001 have shown that buyout, there may be a few who refuse to leave, increasing the risk of making the process very long and more expensive.

Managing a relocation/buy-out program can be difficult because of situations where the majority of residents who favor a buy-out do not want to be penalized by the minority who choose to remain.

INSTITUTIONAL CONTROL OPTIONS

Zoning...

Zoning laws may be very effective at reducing new public exposure to subsidence-prone areas.

With reliable mapping of subsidence-prone areas, zoning can be used to designate areas suitable for new developments of various types.

Zoning based on subsidence potential maps can designate areas with the highest subsidence potential as off-limits areas, lower subsidence potential areas for open space uses, and still lower areas for parking lots or commercial developments where structural considerations make development a low-risk issue.

Areas with the lowest potential for subsidence may be zoned residential and retail.

Zoning will not eliminate the possibility of subsidence, but it can reduce the public and private costs when subsidence does occur.

Special Building Codes...

The safety and structural integrity of buildings constructed over subsidence-prone areas may be significantly improved by using certain construction practices.

Counties and local governments can implement building codes that require these practices for new construction in subsidence-prone areas.

Special building codes are similar to zoning in that they do not eliminate the possibility of subsidence.

However, special building codes differ from zoning in that they allow for more construction and development in higher-potential subsidence areas.

SCREENING OF OPTIONS TO ADDRESS SUBSIDENCE

Table 9.1 presents a generalized matrix for decision makers to evaluate options presented in this report.

The table presents the implementability/constructability, effectiveness, time frames and initial and long term costs of the options.

The options presented in this article are categorized into three types

Investigative Options...

are those methods that assess the condition of the mine workings and/or the ground surface through non-intrusive or intrusive means, i.e. geophysics, drilling or infrared photography, but only yield information at a particular point in time and do not provide constant monitoring of mine conditions.

Predictive Options...

are those that require a continuous monitoring of the ground surface or mine workings to provide an early warning of possible changing conditions which may lead to a subsidence event.

Mitigative Options...

are those options that provide stabilization of areas, prevent access (fencing), prevent placement of infrastructure (zoning), or prevent placement of structures not properly designed or reinforced to withstand subsidence (building codes) in areas that are predicted to have future subsidence.

Previous sections provide detailed descriptions of the options presented

REFERENCES

Luza, K. V., 1986, Stability Problems Associated With Abandoned Underground Mines in the Picher Mining Field, Northeast Oklahoma, Oklahoma Geological Survey, Circular 88, 114 p.

NOTES:

Costs Low $200,000

Medium 200,000-$2 Million

High $2-50 million

Very High $50million

NA – Not applicable

Implementable/Constructable –

the degree to which an option presented is able to be put into effect or is able to be constructed according to a definite plan or procedure Effectiveness – the degree to which the options presented are able to achieve stated goals as judged in terms of both output and impact

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Ku Klux Klan at Douthat, Oklahoma The Blue Card Union was the mine operators union Picher Lion's Club businesses William C. Jones and wife Elizabeth L. Jones was the first to set up a business in Picher Oklahoma. They came to Picher in late 1914. They came from Vinita Oklahoma and started operating the first grocery wagon in the mining settlement. In Lizzie Jones obituary dated February 3, 1946 from the Joplin Globe newspaper, she was referred to as “The Mother of Picher.” Roger's Hotel, Garage and Taxi Roy's Cafe Hot Tamale Butch Livingston's Store Thotnton's Grocery Store Tinsley's Hardware Store Harry Dodson Shoe Repair Lola Giles Steam Laundry Coyne Lumber and Hardware Store J A and H O Green Barber Shop Roxie Theatre Post Pool Hall Burt and Margaret Luther BarPicher Phone Company Southwestern Bell John and Carl Randolph Shoe Store Lion Supply Store Howard Martin Grocery Safeway Store Scott Livingston Store Atwoods Coney Island Diner Harpers Grocery Sample Shoe Store Osborn Cut Rate Drug Plaza Theatre The WhiteWay Bar Brass Rail Bar The Old Mystic Theatre THe Winter Garden Theater The Gayetie Theater Liberty Candy Kitchen Connell Hotel Big Four Garage The Rex Blliard Parlor Connell Bar Connell Coffee Shop Connell Beauty Shop Denton's Store Aragon Cafe Harry Poynter Garage Todd's Funeral Home Central Drug Store Todd's Ambulance service Francis Dry Goods Store Francis Apartments and sleeping rooms Nebel's Grocery Store Ott's Grocery Picher Coke Plant Garner Family later owned a produce and poultry plant King Jack Newspaper Tri- State Tribune Durnill Funeral Home Picher Fire Department Jennings Grocery Bert Luther's Schlitz Bar Economy Cash Grocery Store, Picher Hospital Madolyn's Beauty Shop Ludwigs Store indian Joe's Bar Spaulding Drug Store Bank Of Picher Double Dip Ice cream Parlor First State Bank of Hockerville Oklahoma American Hospital Royal Hat Shop Kemph's Dress Shop Doctor E Albert Aisenstadt Alberta Lee Apartments Rexall Drug Store American Hospital Annex to house the catholic nuns that ran the hospital KGGF Radio Station Bert Luther's Cash and Carry Grocery Gooty's Ready To Wear Doctor Matt Connell Doctor Dell Connell The Men's Club Picher Oklahoma's first post office was established on June 2,1916 John Jackson Holt was appointed the first postmaster Bethal Freewill Baptist Church Assembly of God Church Baptist Church Ned Aitchinson's 5-10-25 cent store American Zinc Institute the Railroad Eating House Restaurant American Legion Teen Town Doctor Berry Doctor De Tar's Cottage Doctor Ritter Livingston's Store Scott Livingston's Roger's Hotel, Garage and Taxi Roy's Cafe Thornton's grocery Tinsley's Hardware Store Picher Steam Laundry Coyne Lumber and Hardware Store Ladies Club Picher Masons J A and H O Green Barber Shop Piokee Mine Lula Bell Mine Central Mill Blue Goose Mine Crocous Mine New York Mine The New York Mine,Cortex-King Brand Mines Company Turkey Fat mine Crawfish Mine And MIll Skelton Mill John Beaver Mine Evans Wallower Mine Picher Mine No. 20 Black Hawk Mine Webber Mine Kerr Photography Studios Sample Shoe Store Frisco Depot Commerce Royalty and Mining Company Jones Grocery Store Picher Mining Camp Picher Oklahoma was incorporatedom March 4,1918. Nancy Jane Mine Eagle Picher Netta Mill Vantage Mine Central Methodist Church Methodist Church Premiere Mine Picher Mine # 6 Piokee Mill and White Lease St Joe GoldenRod Mine # 5 Holiness church Rammage Mine Railroad Station House Skelton Mines Eagle Picher Power Plant Kitty Mine Blue Bird Mine Nazarene Church Pelligan Chat Manufacturing Company Admirality Mine Number 4 Black Mine Blue Goose Mine Number 10 English O Shaft Saint Louis Sand and Rock Company Golden Rod Number 9 Mine Hum Bah Wat Tah Mine Number 3 National Zinc and Lead Company No 4 Mill Hoisters Underwriters Number 2 Mine O.W. Connor Barber Shop Gordan Mine Gordan mine Federal Mining and Smelting Company Gordan and Chief Mines Blue Mound Century Mining Company Central Mining Company Montreal Mine

Picher Twister Home Page | Picher Twister Entry
Tar Creek OU4 Superfund Site Record Of Decision Documents
Picher Superfund Site | The Picher, Oklahoma Buy Out | Tar Creek Documents
Picher Editorial Cartoons/Print Off Coloring Pages
Welcome To Grand Lake | 2008 Grand' Events | 101 Things To Do On Grand Lake
Weather On Grand Lake Right This Minute! |
History of Grove, Oklahoma | Grove's Rich Heritage | Grand Lake History
Cities That Surround Grand Lake | Cayuga Mission | Pennsacola Dam
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"The Great Paper Caper" | Awards & Citations
Pray For Our Country | Dedication | Mission Statement
Grand Lake O' the Cherokees is located in Northeastern Oklahoma Featuring 46,500 acres of water with a distance of 66 miles in length with over 1,300 miles of beautiful shoreline... WATER' You Waiting For?