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Document Title:
Assessment of contaminants associated with coal bed methane-produced water and its suitability for wetland creation or enhancement projects
AUTHOR(S):
Pedro Ramirez Jr
REPORT NUMBER:
R6/721C/05
PAGES:
1 - 50
PUBLICATION DATE:
November 2005
ABSTRACT:
Extraction of methane gas from coal seams has become a significant energy source in the Powder
River Basin of northeastern Wyoming. In Wyoming, coalbed methane (CBM) gas is extracted by
drilling wells into coal seams and removing water to release the gas. Each CBM well produces an
average of 10 gallons per minute (gpm) of water and a maximum of 100 gpm. Disposal of CBM
produced water is accomplished by direct discharge to surface drainages, and also by a variety of
other treatment and disposal methods. Untreated CBM produced water discharged to surface
drainages is the primary method of disposal provided that the CBM produced water meets Wyoming
water quality standards. Water failing to meet water quality standards cannot legally be discharged
into surface drainages and is alternately discharged into closed containment ponds for soil-ground
water infiltration and evaporation. In 2000 and 2001, we collected and analyzed water from CBM
discharges and receiving waters and sediment and biota from CBM produced water impoundments.
In 2002, we collected and analyzed water from CBM closed containment impoundments. All the
samples were analyzed for trace elements. The biota included pondweed (Potamogeton vaginatus),
aquatic invertebrates, fish, and tiger salamanders (Ambystoma tigrinum). One CBM produced water
discharge exceeded the chronic criterion for iron and several CBM produced water discharges
exceeded the acute criterion for copper. Terminal sinks receiving CBM produced water have the
potential for the eventual increase in trace element concentrations in water, sediment and wildlife
dietary items such as pondweed and aquatic invertebrates. Waterborne copper, iron, lead, and
manganese exceeded chronic criteria in several impoundments receiving CBM produced water.
Arsenic, cadmium, nickel, and zinc in sediments from a terminal sink receiving CBM produced water
exceeded the threshold effects concentrations for sediment-dwelling organisms. Cadmium and
chromium in aquatic invertebrates and pondweed, respectively, from terminal sink sites were
elevated. Waterborne selenium concentrations in six of the seven closed containment impoundments
and all seven associated CBM discharges ranged from 2.2 to 8.4 :g/L, exceeding the 2 :g/L
threshold for bioaccumulation in sensitive species of fish and aquatic birds. Closed containment
ponds containing high selenium water may present a risk to aquatic birds using these ponds if the
ponds provide a dietary route of exposure through submerged aquatic vegetation or aquatic
invertebrates. CBM operators, land managers, and landowners should evaluate the disposal options
for CBM produced water on a site by site basis to prevent adverse impacts on soils, groundwater, and
surface water as well as fish and wildlife and their habitats.
PUBLISHED BY:
U.S. Fish and Wildlife Service
DOCUMENT LINK:
http://www.fws.gov/mountain-prairie/contaminants/papers/documents/R6721C05.pdf, 2 MB
ADDITIONAL LINKS:
U.S. Fish and Wildlife Service - Mountain-Prairie Region, Contaminants Program
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