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Chat

 

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Overview


Chat is a fine gravel waste left over after ore production - primarily zinc and Lead mining - that can contain high amounts of toxins. Ore production consisted of grinding and crushing mineral rocks to smaller sizes in order to separate the ore and the "dry" process, as opposed to the "wet" processes that used ponds and are called tailings, produces chat. Huge amounts of chat were left in piles around the Mining sites and large amounts of toxic chat are still reused in different settings (see #Additional Uses of Chats). Chat contains high levels of Lead, zinc, and Cadmium (Cd) that can leach into groundwater, be eaten by livestock, contaminate local wells, and be blown from piles to neighboring areas (#KSGS, 2005).

Chat Production and Background


Chat is produced as a byproduct of Lead and zinc mining and is most prevalent around the Tri-State Area and the Old Lead Belt area in the Midwest (#EPA Region 7, 2007). Chat typically ranges in diameter from 1/4 to 5/8 inch and can contain dangerous levels of different metals (#EPA, 2007).

Geographical Areas


Lead and zinc Mining which produces chat in the Midwest has been centered in two major areas: the Tri-State Area including parts of Kansas, Missouri, and Oklahoma and the Old Lead Belt (#Kring, 2007). Another notorious area for chat pollution located in the Midwest isthe Tar Creek Superfund site (#Tar Creek Superfund Task Force, 2000).

Health Effects


The adverse health effects of chat are directly related to the contaminants that exist in it. Most chat from the Midwest sites highlighted above contain Lead, zinc, cadmium and the health reflects are associated with the health effects of those metals.

Physical and Environmental Effects


Main Articles: Tri-State Area, Old Lead Belt, Tar Creek, Viburnum Trend

Generally the environmental effects of chat are those associated with the contaminants that exist in it, which are often Lead, zinc, and cadmium.

Common hazards left by mines are open mine shafts, collapsed mine shafts, and "subsidence areas" which are basically collapsed mines after all the pillars are mined or weakened (#KSGS, 2005).

When the mines are closed, often times the tunnels become contaminated by the metals still present. This contaminated water can lead to contaminated water sources (#KSGS, 2005).

Additional Uses of Chat


From (#EPA, 2007):

Acceptable Uses of Chat in Transportation Construction Projects

 

EPA has determined the following uses of chat in transportation construction projects funded, in whole or in part, with Federal funds are not likely to present a threat to human health and the environment:
1) Chat used as an aggregate in: hot mix, warm mix and cold mix asphalt road surfaces, asphalt road base, asphalt slurry seals/microsurfacing, and epoxy bridge anti-skid surfacing.

2) Chat used as an aggregate in: Portland cement concrete (PCC), granular road base, stabilized road base, chip seals, and flowable fill if:

  • (a) the product is tested using the Synthetic Precipitation Leaching Procedure (SPLP, EPA SW 846 Test Method 1312) and the resulting Metals in the leachate do not exceed the National Primary Drinking Water Standards Maximum Contaminant Level (MCL) for Lead of 0.015 mg/l and cadmium of 0.005 mg/l and the leachate also does not exceed the National Recommended Water Quality Criteria chronic standard for zinc of 120 ug/l: or
  • (b) EPA (or a State environmental Agency, if it chooses to do so) has determined, based on a site-specific risk assessment and after notice and opportunity for public comment, that leachate will not cause an exceedance of the National Primary Drinking Water Standards Maximum Contaminant Level (MCL) for Lead of 0.015 mg/l and cadmium of 0.005 mg/l in potential drinking water sources, and the fresh water National Recommended Water Quality Criteria for zinc of 120 ug/l in surface waters, or

    3) The use of chat has been authorized pursuant to a state or federal response action. State or Federal response actions are undertaken pursuant to applicable Federal or State environmental laws and with consideration of site-specific risk assessments.

Acceptable Non-Transportation Uses of Chat in Cement and Concrete

 

The Agency recommends that the non-transportation uses of chat in cement and concrete be limited to non-residential construction projects that, on a case-by-case basis, either:

  1. Synthetic Precipitation Leaching Procedure (SPLP, EPA SW-846 Method 1312) tests conducted on the proposed material show that concentrations in the leachate do not exceed the National Primary Drinking Water Standards for Lead of 0.015 mg/l and cadmium of 0.005 mg/l and the fresh water chronic National Recommended Water Quality Criterion for zinc of 120 ug/l; or
  2. EPA (or a State environmental Agency, if it chooses to do so) has determined, based on a site-specific risk assessment and after notice and opportunity for public comment, that leachate will not cause an exceedance of the National Primary Drinking Water Standards Maximum Contaminant Level (MCL) for Lead of 0.015 mg/l and cadmium of 0.005 mg/l in drinking water sources, and the National Recommended Water Quality Criteria for zinc of 120 ug/l in surface waters.

Other Uses of Chat that EPA Believes Will Not Generally Harm Human Health or the Environment:

  • Applications that encapsulate chat as a material for manufacturing a safe product or as part of an industrial process (e.g., glass, glass recycling) where all waste byproducts are properly disposed.

Chat Uses that Have Caused or Have the Potential to Cause Damage to Human Health or the Environment:

  • Use as unencapsulated surface material.
  • Fill material in yards, playgrounds, parks, and ball fields, schools or daycare
    centers.
  • Playground sand.
  • Vegetable gardening in locations with contaminated chat.
  • Sanding of icy roads.
  • Sandblasting with sand from tailings ponds or other chat sources.
  • Bedding material under a slab in a building that has underfloor air conditioning or heating ducts.
  • Development of land for residential use (e.g., for houses or for children's play areas, such as parks or playgrounds) where visible chat is present or where the Lead concentration in the soil is equal to or greater than 500 mg/kg unless the direct human contact health threat and environmental risk is eliminated by engineering controls (e.g., removing the contaminated soil or capping the contaminated soil with at least 12 inches of clean soil).
  • Use of remilled asphalt roads containing chat on residential properties as fill material or placed on residential property for the homeowner's future use.
  • Use as an agricultural amendment.
  • Use of chat piles for recreation (e.g., ATVs, bicycling, hiking, climbing, sliding).

References



Kansas Geological Service (KSGS), "Lead and Zinc Mining", last updated May 5, 2005, accessed 3-27-08.


Environmental Protection Agency, Region 7, "Fact Sheet", July 2007.


EPA. "Tri-State Mining District - Chat Mining Waste". June, 2007.


Gov. Frank Keating's Tar Creek Superfund Task Force, "Alternatives for Assessing Injuries to Natural Resources at the Tar Creek Superfund Site Ottawa County, Oklahoma," Report to the Natural Resource Damage Subcommittee, July 21, 2000.

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