ARCHIVED REPORTS XR0010906 - Laserfiche WebLink

Home Browse Search

k% only in soil samples collected from MW-6. The highest TPH-g result was 39 mg/Kg, revealed in the sample collected from MW-6 at 15 feet bsg. TRPH-d results were nondetectable except for 8 mg/Kg of weathered diesel revealed in the sample collected from MW-5 at 5 feet. Ground water had been encountered during the drilling of each boring at a depth of L'. approximately 18 feet bsg. Two-inch-diameter, Schedule 40 PVC well casing with 0.020-inch factory slots was placed from 30 to 10 feet in each well. A threaded end cap was installed on each bottom. Two-inch-diameter, blank, Schedule 40 PVC casing was extended from the top of the screen at 10 feet bsg to a few inches below surface grade (bsg). Number 3 Monterey sand was used as filter pack and was placed to extend from the bottom of the wells to approximately one foot above the screened interval in the annular space of each well (30-9 feet bsg). The bentonite seals at 9 to 71/2 feet bsg were hydrated with five gallons of potable water. Portland cement was pumped into the remaining annular space above the bentonite seals to extend from 71h feet to 1 foot bsg in each well. Locking caps were placed on top of the well casings inside 8-inch, water-tight street boxes cemented into place at the surface. Monitoring wells MW-4, MW-5, and MW-6 were developed on June 20, 1994 using a stainless steel bailer. Bailing removed turbid water from the wells until clear water appeared. The monitoring wells were sampled after a minimum of 50 gallons were bailed and the ground-water levels had recovered to at least 90% of their static levels. Monitoring wells MW-4, MW-5, and MW-6 were first sounded on June 24, 1994. Utilizing a Keck' interface probe, the W.W. Irwin, Inc. staff technician intercepted the piezometric surface `- in each well at a depth averaging 14.82 feet bsg. The soundings were converted using well casing-top elevations established on June 13, 1994 by Duane Kimball, Modesto-based, California-licensed Land Surveyor No. 4378. The elevation data were used to calculate the present ground-water flow direction and gradient by the three-point method. Ground-water samples collected from MW-4, MW-5, and MW-6 were received at Sherwood 1 Labs on June 21, 1994. The analytical results revealed wholly nondetectable concentrations of TRPH-d analytes and nondetectable results for TPH-g and BTEX analytes in samples collected from monitoring wells MW-4 and MW-5. The results of the analysis of the sample collected from MW-6 indicated that the ground water underlying that vicinity was significantly impacted with TPH-g and BTEX analytes well above the Maximum Contamination Levels (MCLs) set by the California Department of Health Services. I Interim Ground-Water Monitoring Activities The SJCPHS-EHS then required that ground-water monitoring be undertaken for six months, from August 1994 through January 1995. Samplings of MW-4, MW-5, and MW-6 were performed in September and December of 1994. Soundings were performed monthly. Local W.W. Irvvin, Inc. Project No. 33016.06 ",'' Apri11996 5