A word about reservoir reclamation

BY: BRENDA K. SCHLADWEILER, PhD.

The Bureau of Land Management (BLM) requires all reservoirs (im- poundments) constructed for the management of water produced in association with Coalbed Natural Gas (CBNG) be completely removed and reclaimed when production involving those reservoir(s) has ended. Although final specific BLM guidance, as directed by the Buffalo Field Office (BFO) for those offices dealing with such reservoirs, is not currently available, three phases will likely be considered for reservoir reclamation: Notice of Intent to Abandon Impoundment; Channel and Reclamation Plan; and Final Abandonment. The first phase is generally back- ground information gathering, the second being the proposed plan of reclama- tion based on the background report in part, and the third being the monitoring phase.

NOTE: The following summary of such requirements, in part, is generally based on the following documents: ) draft guidance by the BFO BLM for im- poundment reclamation guidance; and, 2) WDEQ Implemention Guidance for Reclamation and Bonding of On-Channel Reservoirs that Store Coalbed Natural Gas Produced Water (June, 2009). Final guidance on a specific project should AL- WAYS be discussed with the appropriate regulators PRIOR to project initiation.

Phase I or background information is a description of the existing site conditions before impoundment occurs or has occurred since many of these reservoirs pre-date final BLM guidance. Historical aerial imagery can be helpful to document infor- mation such as headcut or spring locations that may impact site stability and reclamation success. Consideration for stable channel flows through the reservoir, as well as below the reservoir should be taken. If successful reclamation is to occur, the erosivity of relatively unconsolidated, silty sediments will be an issue. Reservoirs built on former headcut locations will have large-scale issues as well. Erosion controls for flatter gradient channels will differ from those for steeper channels.

Phase II or the reclamation plan should include all considerations in the design and implementation of engineered structures, if needed, and reclamation techniques. The drainage area extent above the reservoir and anticipated storm event sizes should be determined and the channel slope between the upper and lower boundaries calculated. The availability and extent of previously salvaged or in-place topsoil or suitable plant growth material should be determined.

Collection and analysis of reservoir bottom sediment will be helpful in directing the overall reclamation plan and reducing overall costs. Analysis of bottom sediment will determine if this sediment must be excavated and removed or reclaimed in place, if a barrier is required to prevent upward migration of salts or metals, and if soil amendments are required. Specific parameters to test the bottom sediment should be based on historical soil and water quality data, along with anticipated salt, sodium, and/or fertility issues.

Appropriate seed mixes will be identified as part of the reclamation plan. Mulching may occur in areas where recontoured material is at risk of erosion based on soil texture and the character of the recontoured landscape. If mulching material is used, such material should be certified weed-free. Fencing may be needed to minimize grazing impacts. Erosion control measures and storm water diversions should be applied to reduce erosion.

Phase III or reclamation monitoring should be completed for a minimum of two growing seasons after reclamation to document success and recommend followup proce- dures as needed. A geodatabase should be used to track such changes over time, including the effort that went into the original reclamation and any followup procedures.