Section 8 - Investigation Derived Waste

Investigation-derived waste (IDW) may include soil cuttings, drilling fluids, decontamination fluids (water and other fluids), and disposable personal protective equipment. The removal excavation and the drilling contractors will be responsible for bringing and/or constructing decontamination areas at the site sufficient for the anticipated activities, as well as containing and managing produced solids and fluids. The air rotary drilling method may produce significant volumes of drill cuttings and groundwater. Past experience shows that managing the drill cutting can be expensive and time-consuming. Parsons will evaluate two management techniques for this task order, a lined impoundment storage pond or portable temporary storage containers.

8.1 - Lined Surface Impoundments

Pending regulatory approval, Parsons and CSSA prefer to construct lined surface impoundments for retention of all drill cuttings and mud. The impoundments will be used for short-term (less than 90 day) storage of the drilling-generated media. The utilization of retention ponds will reduce or eliminate delays and costs associated with settling and disposing of drill cuttings on a case-by-case basis. IDW with a high solids content (drilling fluids) would be transported and discharged to a surface impoundment. IDW with a low solids content (decontamination water) will be transported to the on-post treatment plant for eventual treatment and discharge to permitted Outfall 002. This option is being further evaluated, and a detailed plan will be provided as a separate deliverable at a later date. This alternative requires significantly less confirmation sampling and downtime associated with laboratory analysis and approval. However, significant engineering costs, a background evaluation of selected sites, costs associated with any permitting requirements, and issues with eventual pond closure, are factors to be considered.

In this alternative, the excavation and drilling contractors will be responsible for transporting all generated drilling fluids to a centrally located impoundment area within the facility. Depending on the circumstances, two smaller ponds may be constructed to be more proximal to the planned areas of investigation, thus reducing transport times. Multiple transportable 20- to 30-yard roll-off boxes may also be placed near the drilling locations to temporarily contain drill cuttings if production occasionally exceeds the transportation capability of the drilling contractor. Depending on availability, machinery for transferring cuttings from wellhead containment areas to the roll-off containers can be provided by CSSA.

8.2 - Temporary Storage Containers

The traditional alternative is to use multiple 20- to 30-yard roll-off boxes to temporarily contain drilling fluids. Drill cutting are placed directly into the containers at the site to settle and decant solids from the drilling mud. This process may take days for a single roll-off to sufficiently settle, and may create a capacity problem while drilling high production intervals. Once the solid fraction has sufficiently settled, the liquid fraction of a roll-off container can be characterized for a short list VOCs (Table 1.1) to determine if the water will meet surface discharge requirements (less than MCLs). The liquid fraction of each roll-off is sampled to make the discharge determination. One issue with the liquid fraction analysis is that the presence of residual surfactants from drilling foam will foul an analytical gas chromatograph (GC) at elevated concentrations. A good field test for determining whether analysis on the liquid fraction is feasible is to mix one part roll-off water with nine parts deionized water in a clean unpreserved glass jar. Upon agitation of this field sample, if foaming action is observed within the sample, the roll-off requires more time to settle. Table 1.1 estimates the number VOC water screening samples that may be required in association with IDW activities.

Once a roll-off container is sampled, the determination to discharge water is based on the analytical results being less than the MCL (or Tier 1 PCL) for a particular compound. The determination of releasing uncontaminated groundwater is made in conjunction (and permission) of the CSSA environmental officer. Discharges to the surface are made to areas that do not have the potential for draining off-post. The roll-off may then be reused to store drilling fluids. Once the roll-off has a umulated approximately 50 percent solids, the container should not be used to store additional fluids until the solid fraction can be characterized and removed from the roll-off.

Any remaining mud/solids should be sampled for the short list of VOCs (Table 4) for characterization. Solids with VOC concentrations less than the method detection limit (MDL) can be transported and disposed onsite as fill material. Detectable concentrations of VOCs will require offsite landfilling. Samples will be collected and analyzed for disposal parameters as indicated in Table 1.1, to secure appropriate landfill approvals. Once the container is emptied, it may be re-lined and reused for storage. Table 1.1 estimates the number of VOC soil screening samples that may be required in association with IDW activities.

Additional roll-off boxes (covered, lined, and leak-proof) will be placed near the water treatment plant for processing of well development groundwater through a GAC unit. Contaminated groundwater produced during well development will be transported by the drilling contractor to these roll-off containers via vacuum truck for eventual treatment and discharge to permitted Outfall 002.

This process can be costly with respect to the culmination of both analytical costs and delays in drilling related to storage capacity problems. However, this will be the primary method of IDW handling until the lined impoundment method is approved and constructed.

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