SAP Addendum Specific to Delivery Order TO 0008

Section 4 - Investigation-Derived Waste Handling

IDW may include purged groundwater and decontamination fluids (water and other fluids). The field sampling team will be responsible for containing and managing produced fluids.

4.1 - Granular Activated Carbon at Outfall 002

During this project, Parsons will maintain and operate the CSSA GAC unit located at Outfall 002. The operation and discharge limits are governed by the CSSA TPDES permit (Volume 6-2, NPDES). The purpose of the GAC unit is to treat small quantities of contaminated groundwater generated during investigative activities, and properly discharge it to the permitted outfall. The average outfall flow rate is permitted at 30,000 gallons per day, which is approximately 20.8 gallons per minute (gpm) over a 24‑hour period.

In general, the GAC unit is comprised of a small centrifugal pump, cartridge-type pre-filters, two 200-pound GAC canisters, and meters that monitor the discharge. Water to be treated may be introduced into the system via a 500-gallon tank located within the building, or be pumped in from external rental tanks (or roll-off boxes) outside the building. The system can be operated in either a series or parallel configuration. The system is sized to match the daily average flow of 30,000 gallons per day. Each carbon canister is rated for a flow rate of 10 gpm, meaning the system can effectively treat contaminated groundwater at 20 gpm in a parallel configuration, or 10 gpm in a series configuration. Appendix C provides a general schematic view and other operational information for the GAC.

Parsons will be responsible for daily operation and maintenance of the GAC unit. It is imperative that the GAC unit be operated and monitored by those requirements set forth in the TPDES permit. Those operating the unit should familiarize themselves with its requirements. In general, the logsheet must be completed for each treatment operation. The TPDES permit requires that the discharge volume, average flow, instantaneous flow, and pH be monitored for each discharge event. The discharge volume and instantaneous flow can be recorded from the integral flowmeter. Likewise, the instantaneous pH measurement can be recorded from its dedicated meter. Total discharge is measured by recording the flow totalizer measurements before and after treatment. The instantaneous flow readout should be used to control the flow so the discharge rate does not exceed the engineered capacity (10 gpm in series or 20 gpm in parallel). In its current configuration, Valve No. 7 should be used to regulate the discharge rate. Series operation is the preferred configuration because it allows the groundwater greater contact time with the activated carbon.

Filters should be checked regularly, and the pressure gauge monitored often for indications that the filters are becoming fouled. Both 1 micron and 5 micron filters are used to prevent suspended sediments from fouling the carbon canisters. In series, a 5 micron filter in filter chamber �A� should be followed by a 1 micron filter in chamber �B�. In parallel operation, both filter chambers �A� and �B� should be fitted with 1 micron filters. Suspended sediments will dramatically reduce the life of the GAC unit, and any means necessary should be employed to reduce the amount of solids entering the system.

In accordance with the TPDES permit, samples from the GAC treatment will be collected twice during each week the GAC is operated. It is imperative this requirement be met. A monitoring week is defined as starting on midnight Sunday, and ending at midnight on the following Saturday. To ensure that the sampling requirements are attained, the following sampling schedule will be employed.

During the first treatment of the week, three samples will be obtained. At start-up, one sample will be obtained from sample port �A.� At the end of the treatment, one additional sample will be collected from sampling port �A� and one sample will be collected from sampling port �B.� The second pair of samples will be submitted for PCE and TCE analysis, while the first sample is retained on ice in the sample refrigerator. If the GAC unit will be operated one or more times before the end of the week, one additional sample will be obtained at sample port �A� before the end of the treatment cycle, and the stored sample will be discarded. However, if the GAC unit is not operated at any other time that week, the first sample collected will be submitted for analysis. All samples will be analyzed with a 7-day turn-around-time.

The GAC unit log will be maintained at all times. In addition, maintenance records will be kept updated on the GAC log as well as the dry-erase board located within the GAC building. Filters also need to be inventoried on a bi-weekly basis. A copy of the GAC unit log will be provided to the CSSA Environmental Office and faxed to the project manager every Friday so the monthly reports can be generated.