|
r �
<br /> S ECOR
<br /> Ms. Vicky McCartney
<br /> March 29, 2004
<br /> Page 4
<br /> Also in late 1999, Cambria conducted a sensitive receptor survey. Based on a review of United
<br /> States Geological Survey (USGS) topographic maps and recent area maps, an unnamed levy-
<br /> restricted slough was identified within 2,000 feet south of the site, and a man-made lake was located
<br /> in a residential area approximately 1,500 feet southwest of the site. Well logs obtained through the
<br /> State of California,. Department of Water Resources (DWR) indicated the presence of an irrigation
<br /> well owned by the California Department of Transportation (Cal-Trans), which was screened from
<br /> approximately 214 feet to 350 feet bgs and located approximately 315 feet west of the site (Cambria,
<br /> 1999). According to Cambria, the Cal-Trans well had been destroyed in preparation for
<br /> reconfiguration of the Interstate 5 and Hammer Lane interchange (Cambria, 2000). According to Mr.
<br /> Witzak Gilon of the City of Stockton Municipal Water System (CSMWS), there were no CSMWS
<br /> water supply wells located within the 2,000-foot search radius (Cambria, 1999).
<br /> On June 12 and 13, 2000, Cambria replaced MW-1 and damaged Well MW-2 with groundwater RIs°
<br /> monitoring wells MW-1 R and MW-2R. In addition, Cambria drilled and installed two 2-inch diameter 0,1
<br /> wells (MW-9 and MW-10) to a total depth of 31.5 feet bgs. Laboratory analysis of soil samples
<br /> collected from the soil borings detected maximum concentrations of TPHg at 0.82 mg/kg (MW8-12')
<br /> and MtBE at 2.6 mg/kg (MW8-30). BTEX was not detected above laboratory detection limits.
<br /> Laboratory analysis of groundwater samples collected from all wells detected maximum
<br /> concentrations of TPHg at 3,400 µg/I- (VW-1), benzene at 84 µg/l_ (VW-1), MtBE at 250,000 µg/L,v''v i
<br /> and TBA at 17,000,A4g/L (MW-2R) (Cambria, 2000).
<br /> In August 2000, GR implemented an interim migration control plan at the site to reduce the amount
<br /> of:petroleum hydrocarbons and MtBE beneath the site, and to prevent further off-site migration of the
<br /> dissolved plume (GR, 2000). The plan consisted of the periodic extraction of approximately 5,000
<br /> gallons of impacted groundwater from wells historically containing the highest concentrations of
<br /> petroleum hydrocarbons and MtBE (MW-1R, MW-2R, and VW-1). This interim remediation
<br /> technique continues to be performed at the site on a weekly basis by Onyx Industrial Services
<br /> (Onyx).
<br /> In November 2001, SECOR conducted a five-day dual-phase extraction (DPE) test to reduce the
<br /> amount of petroleum hydrocarbons in soil and groundwater beneath the site, and to determine the
<br /> feasibility of DPE as an applicable technology for remediation at the site. DPE tests were performed
<br /> on well MW-1 R for 3 hours, MW-2R for 3 hours, VW-1 for 2 hours, and simultaneously on wells MW-
<br /> 1R, MW-2R, and VW-1 for 92 hours. DPE was conducted at vapor extraction flow rates ranging
<br /> between 10.90 standard cubic feet per minute (scfm) to 42.86 scfm, at vacuums ranging from 14 to
<br /> 25 inches of mercury, and at groundwater extraction flow rates ranging from 0.01 gpm to 6.2 gpm.
<br /> During DPE testing, an estimated 8.11 pounds of TPHg, 0.17 pounds of benzene, and 5.26 pounds
<br /> of MtBE were removed from beneath the site, and approximately 26,210 gallons of impacted
<br /> groundwater were extracted and transported off-site for disposal. Based on the results of DPE
<br /> testing, this technology was determined to be ineffective based on the low soil vapor extraction
<br /> radius of influence calculated for simultaneous application of DPE (24 feet), the large quantity of
<br /> extracted groundwater, and low estimated mass removal quantities (SECOR, 2002).
<br /> PROPOSED SCOPE OF WORK
<br /> The proposed scope of work will involve an initial phase CPT boring installation followed by a second
<br /> phase of HydroPunch® groundwater sampling based on the results of the CPT assessment.
<br /> Proposed CPT soil boring locations are shown on Figure 1. Location CPT-1 is intended to evaluate
<br /> I:1ConocoPhi11ips1111931Work Plans\IRAP&Oft-Site Asmt WP Addendum v 2.doc SECOR international Incorporated
<br />
|