ARCHIVED REPORTS XR0011751 - Laserfiche WebLink

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... Work Plan for Refined Plume Definition and Management of Floating Product-7500 W 11th St., Tracy, CA. Page 51 personnel be permitted to enter the open cut-off trench, unless at the time they enter, its walls are stable and the trench is less than 5 ft deep. However, if it proves necessary during active excavation, or if, in the opinion the engineer in responsible charge of the work, it may ... become necessary at some time during the two-week period over which it is planned to hold the trench open, a hydraulic jack and plywood sheeting shoring system will be installed in the trench to ensure the stability of its walls. As is discussed in Section 9.4.1.5 below, should the �. floor of the trench threaten to become unstable due to development of flowing sand conditions or other deleterious circumstances, the project engineer will direct sufficient crushed rock to be placed into the trench to maintain its stability. Note: r All underground construction described in this section will be performed by a qualified contractor holding a General Engineering Class A contractor's license with hazardous waste endorsement issued by the California State Contractors Licensing Board. 9.4.1.3 Soil Sampling in Cut-off Trench To extend present understanding of the lateral and vertical extent of analytes of concern in the subsurface in the area around Monitoring Well MW-7, the walls and floor of the cut-off �., trench will be sampled at vertical intervals of not greater than 10 ft, and at lateral intervals of 25 ft. along the length of the trench. To obtain each sample for analysis, an intact block of soil will be excavated from the target location and raised to the surface in the excavator bucket. A face of the block of soil in the bucket will be cut with a shovel to expose an undisturbed surface and a clean, 2-in. diameter by 6-in. long, brass sampling tube will be driven into the cut soil face until the tube is completely filled with soil. +•- Following sample recovery, each sample tube will be cleaned externally, its ends covered with a Teflon sheet and closed with tightly-fitted plastic caps. The caps will be secured with adhesiveless tape. Each sample tube will be labeled for identification, entered into chain-of- custody control and packed on chemical ice for transport to STL's laboratory in Pleasanton, California. +- 9.4.1.3.1 Analysis of Soil from Trench Bottom and Walls Each soil sample submitted to the laboratory will be analyzed for the following suite of analytes. Anal3je Method of Analysis Total Petroleum Hydrocarbons EPA Method 5030/8015 (quantified as Diesel) v Total Petroleum Hydrocarbons EPA Method 8020A/8015 SJC