COMPLIANCE INFO - Laserfiche WebLink

Home Browse Search

4.3 Field Investigation 4.3.1 Drilling and Soil Sampling The scope of work for this project includes the advancement of up to two soil borings using hollow stem auger(HSA) drilling equipment. Soil borings will be located in accordance with Caltrans' Task Order 10-OA7401-ME. Figure 2 shows proposed boring locations. Soil borings will be advanced to 15 meters(50 feet)below ground surface(BGS) or first encountered groundwater, whichever is encountered first. Discreet soil samples will be collected at 1.6-meter (5-foot) intervals until groundwater is encountered. Soil samples will be field screened using a flame ionization detector(FID) and a photo-ionization detector(PID). Approximately nine soil samples will be collected from each boring. Soil samples will be collected using a split-spoon sampler lined with metal sample tubes. Groundwater samples will be collected from each boring using one or more of the methods described in Section 4.3.2. Drilling and sampling procedures are presented in Appendix A. Following sample collection, the borings will be backfilled with bentonite cement grout from the bottom of the borehole to ground surface. The surface material will be repaired with cold patch asphalt or concrete where applicable. Drill cuttings will be placed into a 208-liter(55-gallon) United Nations-approved drum. All drilling and sampling equipment will be washed prior to use. In addition,to minimize cross-contamination between borings, all appropriate downhole drilling and sampling equipment will be washed between borings. Decontamination water will be placed into a 208-liter (55-gallon)United Nations-approved drum. The horizontal and vertical locations of the borings will be established using a Trimble GPS Pathfindefrm Pro XRS global positioning system (GPS). The GPS utilizes a GPS receiver and MSK radio beacon differential receiver. The GPS is reported to have sub-meter accuracy for horizontal location of the borings. The vertical accuracy is reported to be two to five times that of the horizontal accuracy. The GPS data will be downloaded in the office with Trimble software to provide differential corrections to the coordinates. 4.3.2 Groundwater Grab Sample Collection Groundwater grab samples will be collected from the soil boring locations. The groundwater samples will be collected from well casing inserted into each boring. The well casing will consist of 2.5-centimeter(1-inch) diameter, Schedule 40, flush-threaded, 0.05-centimeter(0.020- inch), machine-slotted polyvinyl chloride (PVC)well screen. The soil borings may be advanced to greater depths depending on the groundwater conditions. If free product is encountered, SAGDP-N..bwncjpl LDrojects18318347601 wkpin&hsp1 wp&hsp HS4 M 110 HSA wp.doc 4_2 4119101