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BLACK & VEATCH <br /> MEMORANDUM <br /> Marley Cooling Tower Company B&V Project 11654.682 <br /> MCTC Subsurface Soil Flushing System B&V File D.3 <br /> Status of Phase II Pilot System June 10, 1991 <br /> To: File <br /> M0,6) <br /> From: Michael A. Williams, B&V <br /> Implementation of the Pilot Soil Flushing System began on May 9, 1991. <br /> Potable city water continues to be injected into IW-1 while the <br /> totalized flow and injection rate are recorded by a flow meter and <br /> verified by visual observations. Initially, the flow rate was higher <br /> than anticipated, approximately 10.5 gallons per minute (gpm) . The <br /> flow rate decreased gradually to between 7 and 8 gpm (see Figure 1 , <br /> attached). <br /> We attribute the observed flow rates to highly transmissive sand units <br /> found in an interbedded zone of sand, silt and clay at approximately 45 <br /> to 60 feet below land surface (bls) and a sand stratum located at <br /> approximately 60 to 65 feet bls. Initial infiltration appears to have <br /> flowed along these preferential zones and has been detected by the <br /> neutron probe gauge at several locations and depths. <br /> The higher than expected flow rates created some doubt as to the <br /> usefulness of the system in flushing the shallow clay material from <br /> approximately 20 to 45 feet bls. Consequently, Black & Veatch <br /> recommended adding two additional shallow injection wells to test the <br /> infiltration into the shallow clay zone. <br /> On June 4, 1991 , the injection rate decreased to between 1. 1 and 1 .4 <br /> gpm, which is similar to our original predicted rate. Therefore, it <br /> appears that the flushing has stabilized. In addition, recent neutron <br /> probe measurements indicate that moisture content elevations may be <br /> present within the shallow clay zone at a distance of 5 feet from the <br /> injection well . Since it appears that the original pilot flushing <br /> system may be adequate to fully evaluate the remediation program, pilot <br /> monitoring will continue as originally proposed. All parties will be <br /> advised if pilot system modifications are reconsidered in the future. <br /> maw file: MEMOPIL.WP5 <br />