Intro

CBM EIS Update

Prepared by

Dan Arthur, P.E. - ALL Consulting

Tulsa, Oklahoma

Highlight of Issues (Partial List)

Hydrology Impacts

Groundwater Drawdown/Recovery

Surface Water Impacts

Water Quality/Degradation

Soils/Vegetation Impacts

Soil Impacts from CBM Water

Impacts to Vegetation

Gas Drainage

Federal – Indian Trust Issues

Socioeconomics/Environmental Justice

Wildlife Impacts

State and Federal Planning Areas

BLM Planning Area

Billings RMP Area

Powder River RMP Area

State Planning Area

Statewide

CBM Emphasis Areas

Powder River Basin

Blaine County

Park County

Gallatin County

BLM and State Planning Areas

Stratigraphy in the PRB (Generalized)

The Powder River Basin of Montana is expected to have the majority of CBM development and was emphasized in

the analysis. Targeted Coals for CBM are Paleocene Fort Union, all of which are in the Tongue River Member

Water Resources

Water Resources Technical Report (ALL, 2001)

Geology & Hydrogeology

Water Use and Quality

Water Resources Impacts

Groundwater drawdown Analysis

Water balance of groundwater resources

Surface water potential impacts

Mitigation and BMPs

Other Studies

Groundwater Modeling (MBMG)

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Best Management Practices (ALL/MBOGC – DOE Project)

CBM Water Characterization

Water Use Map of the PRB

Water Use Map of the PRB illustrating distribution of wells along stream beds

Most water wells are completed in alluvium near stream beds

CBM Development By Watershed

Upper Tongue River has highest potential development 5,800 + wells

Eastern Watersheds have lowest with approximately 225 wells

CBM Water Production Rates

Extrapolation of water production rates over an estimated 20 year life yields an averaged production rate from CBM

wells of ~2.5 gpm. It is also important to note that this is an estimate based on existing data in Montana and data

comparisons from Wyoming. Actual average production may vary from this average assumed rate.

To obtain average production rates for CBM wells in Montana, trend analysis was performed for averaged production

of produced water at CX Ranch. Results were compared to data from Wyoming.

CBM and the Groundwater Balance

Total Groundwater Resources

Estimated 250 billion cu ft of groundwater in coal seams that are expected to be developed in the PRB

Estimated Maximum CBM Production

An Estimated 4.4 billion cu ft of water could be produced by CBM wells per year based on exponential decline

analysis and the RFD’s maximum production numbers in all watersheds of the PRB

Approximately 35% of groundwater resources in the development area would be extracted.

Groundwater Monitoring Analysis

Groundwater monitoring data were obtained for analysis of impacts from CBM production. Several monitoring

stations exist as a result of coal mine activity in the area.

Groundwater Impacts from CBM

Monitoring Well WR-55 (approximately 0.2 miles from CBM operations) shows drawdown after approximately 11

months of production activities at CX Ranch. Drawdowns of approximately 30 ft are observed. Impacts from coal

mining can also be observed.

Potential Surface Water Impacts

Watersheds that would be impacted the most by CBM discharge are those with low flow volumes and low SAR such

as Rosebud (near Kirby) where large increases in flow would result from CBM discharge

Other watersheds with large flows would be capable of receiving CBM water with little impact

Worst Case Surface Water Impacts

CBM development in Wyoming (50,000 potential wells) would overshadow impacts resulting from development in

Montana.

Powder River would have an increased annual average flow of 9% with SAR increasing to ~5. Discharge during low

flow periods could be dramatic.

Little Powder River would have an increased annual average flow of 400% with SAR increasing to ~9.

Increased flows would likely cause increased suspended sediment, erosion, and impacts to wildlife, cultural

resources, etc.

Soils & Vegetation

S il T h i l R t (ALL 2001)

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Soils Technical Report (ALL, 2001)

Characterization Issues

Characterization of CBM water

Crop characterization in the Billing and Powder River RMP areas

Soils Characterization

Impacts of CBM Water

Agricultural irrigation

Livestock watering

Other impacts

Soil Types in the PRB RMP Area

Soils range from loams to clays, but principally loams to silty clay loams

Mean K-Factor for Soils of PRB RMP Area

K-factors are a measure of a soil’s susceptibility to erosion from water. High K-Factors are the most erodible with

values over 0.37. Most soils in the PRB have K-factors below 0.37

Mean Soil Salinity of PRB RMP Area

Most soils in the PRB have low salinity

Higher salinity soils require better management practices to produce crop yields

Statewide Maximum Soil SAR

SAR is a measure of the soil’s sodicity. High SAR values result in decrease infiltration of water. Soils with fine

textures (clayey) are more susceptible to sodicity increases from irrigated water with high SAR

Irrigation Water Salinity and Crop Yield

With normal management practices, the lowest CBM water salinity would have no adverse impacts on crops

More salinity sensitive crops such as alfalfa and corn could be affected by the average salinity CBM water

Highest salinity CBM water could be used as a portion of the irrigation water supply if mixed with other sources of

water

CBM Water Quality Relative to Infiltration

Average CBM water would cause slight to moderate reductions in infiltration

Waters with the highest SAR and lowest EC could cause significant reductions in infiltration

Waters with the lowest SAR and highest EC would cause only slight to moderate reductions in infiltration

Impacts to Soil and Plants from CBM Water used for Irrigation

The use of high salinity CBM water may affect crop production limiting farmers to grow only more tolerant plant

species

The use of water may require farmers to modify cropping practices, new equipment, different crop growth, soil profile

modifications, etc.

Use of CBM water over a number of years may result in increased soil salinity from accumulation

Dispersed soils could experience significant erosion due to lack of structure and vegetation

Encouraging Beneficial Use of CBM Water and Best Management Practices

Low salinity and low SAR CBM water could be used for irrigation

Moderate salinity and SAR water could be diluted with other irrigation water and applied.

Careful monitoring of soils would be required if high salinity and SAR water were used for irrigation, special

management practices would have to be followed.

CBM water does not appear to be harmful for livestock and could be used as new water supplies to pasture land

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were supplies currently do not exist.

Monitoring of Livestock may be required initially as they adjust to the new water supply.

Wildlife, Cultural Resources, and other issues could potentially be impacted by CBM operations. Effective use of Best

Management Practices and Mitigation can serve to minimize impacts from CBM development and cumulative impacts.

Questions?

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