DEVELOPMENT OF SITE SPECIFIC WATER

QUALITY STANDARDS for the TONGUE RIVER, LITTLE POWDER RIVER and POWDER RIVER

November 2000

During the last few years, the region called the Powder River Basin has seen the beginning of an accelerating growth industry, coal bed methane gas. The Powder River Basin contains large coal deposits that have methane gas trapped in the coal aquifers.  It also contains four major rivers three of which flow into Montana.  These are the Tongue River, Little Powder River and the Powder River, all of which begin in Wyoming and then flow into Montana. The Powder River, for example, begins near Casper, WY and flows into the Yellowstone River near Terry, MT.

Methane natural gas has a wide variety of energy-related uses including the heating of homes and generation of electricity.  It is generally considered a cleaner form of energy than traditional sources such as coal and oil.  Most of the coal bed methane development so far has been in Wyoming.  One field, however, is producing gas in the Tongue River Basin in Montana (Redstone Gas Partners near Decker, MT) and several other areas in Montana are being explored.

The methane extraction process involves pumping large volumes of water from the ground to the surface.   The water pressure that is trapping the gas in the coal must be lowered in order to release significant amounts of methane. Water wells are drilled into the coal seam with the casing sealed above the coal.  A standard water pump is used to pump water to the surface. The combined affect of many wells pumping simultaneously is to reduce the water level in the coal aquifer, lowering the water pressure and allowing the methane to escape through the well casing.  The water pumped from the coal aquifer is usually discharged to existing stream channels.  Many of these receiving streams are ephemeral or intermittent. Constructed ponds may receive some of the produced water that may in turn directly or indirectly discharge to an adjacent stream channel.

Because coal bed methane extraction involves the continual discharge of groundwater to the surface, it may cause several substantial water quality impacts in the basin.  Increased flows in these streams from discharge water may damage streambeds and destabilize stream banks.  Ephemeral streams are especially vulnerable to gullying and destruction of vegetation. The chemical quality of the water is also a major concern. The quality of the discharged water varies from one area to another with a greater concentration of dissolved constituents near the Wyoming-Montana border. The parameters of concern include Sodium, Iron, Manganese, Fluoride, Chloride, Ammonia, Silver, Aluminum, Arsenic, Boron, Barium, Cadmium, Copper, Mercury, Nickel, Lead, Strontium, Zinc, Total Dissolved Solids (TDS), the Sodium Adsorption Ratio (SAR), Electrical Conductivity (EC) and Total Suspended Solids (TSS).

The discharge of CBM production water in Wyoming and Montana can increase the concentration of these parameters in our rivers and streams and impact beneficial uses.

Montana has numeric standards to protect human health and has designated beneficial uses for many of these pollutants. Where there are no numeric standards (i.e., SAR, salinity, and flow), the Department of Environmental Quality (DEQ) will translate the general narrative standards in the surface water quality standards into site specific standards.  This process will include a consideration of existing soils, irrigation practices and crops. Thus, input from the water users and soil scientists is necessary.  Where there is remaining assimilative capacity, that is where the water quality for a parameter is better than necessary to support the use of the water, this assimilative capacity may have to be assigned to potential dischargers. Again this process requires input from the affected parties and will probably require formal agreements between Wyoming, Montana, and the Indian Tribes.

Water entering Montana from Wyoming must meet these standards as well as all of the other Montana water quality standards, including nondegradation. CBM development in Montana and Wyoming cannot cause a violation of standards in Montana.

The overall approach to developing numeric site specific standards will be consistent with the target setting approach used in the development of water quality restoration plans and associated total maximum daily loads (TMDLs). Meeting these standards or targets will include developing “wasteload allocations” for point sources and “load allocations” for nonpoint sources. Each stream that enters Montana from Wyoming would be addressed as a point source and assigned a “wasteload allocation”. All allocations would be set at levels necessary to protect the existing quality where a waterbody is not considered impaired, or set at levels lower than current conditions where it is necessary to restore an impaired waterbody. Furthermore, the allocations will incorporate a margin of safety and may allow for future growth opportunities in Montana. 

DEQ is currently working with landowners, local governments, other agencies and interested parties to develop and implement water quality restoration plans. The Tongue, Powder and Little Powder rivers were listed as impaired in 1996 and 1998, but are currently identified as needing more data to make final impairment determinations for the parameters discussed above. It is expected that the process of setting site-specific standards will provide the information necessary to make beneficial use support determinations for these parameters.

The standards and associated restoration or protection plans will be included in the CBM Environmental Impact Statement (EIS). This EIS is a multi-agency effort currently in the planning stage.  DEQ is the designated lead agency for the state of Montana .  Cooperating agencies include the Department of Natural Resources and Conservation (DNRC), the Board of Oil and Gas Conservation, and the U.S. Bureau of Land Management (BLM), Miles City Office.

Ultimately, this work by DEQ is intended to protect state waters and their beneficial uses.  Such uses include drinking water, irrigation water, stock water and aquatic life.  This process must involve all interested parties including land owners who may be affected by CBM development.  DEQ encourages all interested organizations and individuals to take advantage of this opportunity to be proactive and move forward with the development of water quality site-specific standards and water quality restoration or protection plans for these watersheds.