WORK PLANS - Laserfiche WebLink

Home Browse Search

1 Margaret Laggorio Page 2 November 1, 1995 Project 131420.01.04 11 that is located north of NP-2 will be converted to an SVE well. An additional borehole will be drilled at location SB-12 situated to the south of NP-2. Soil samples from this borehole will be screened with a photoionization detector(PID) to determine the relative concentrations of any petroleum constituents. If the field engineer determines that there are sufficient quantities of petroleum hydrocarbons present in the soil,the borehole will also be converted to a SVE well. However, if the concentrations are comparatively low (below 100 ppm)using the PID, then the borehole will be backfilled using Portland cement. The boreholes will be logged by a California-registered Geologist. Soil samples will be recovered every 5 feet and logged according to the Unified Soil Classification System (USCS). These logs will accompany the final report. The base of the proposed SVE wells will be installed to approximately 10 feet below first encountered water and the top of the screens will be approximately 10 feet above first encountered water. Figure 2 shows the proposed general well construction. The borehole will be drilled to approximately 80 feet bgs using hollow-stem auger drilling techniques. The well casing will be flush-threaded schedule 40 PVC, with 0.020 machine slotted PVC screen section. Screen length will be 20 feet and the annular space around the screens will be filled with 2 x 12 graded sand, creating a gravel pack. The gravel pack will be placed up to 2 feet above the top of the screened interval. The well at this point will be predeveloped by the drilling contractor by a combination of bailing and surging groundwater from the casing in an attempt to get the gravel pack to settle. The annular space immediately above the gravel pack will be filled with a 2-foot thick intermediate seal consisting of bentonite pellets. These pellets will be hydrated with 10 to 20 gallons of potable water. Following the placement of the intermediate seal, a sanitary seal consisting of Portland cement and bentonite will be tremied into the borehole. The grout mixture will not exceed 71/2 gallons of water to one 94- pound sack of cement. The surface completion will consist of a flush with grade traffic proof vault box. The wells will be surveyed for horizontal control using an arbitrary bench mark established on the property and vertical control to the nearest 0.01 foot. c:\work\word\del monte\p1ant33\svedri1.doe