WORK PLANS - Laserfiche WebLink

Home Browse Search

+— Work Plan for Extended Site CAWeterization: 7500 West Eleventh Street, Tracy,CA. Page 6 4W 6.0 PROPOSED EXTENSION OF SITE CHARACTERIZATION ,.. To comply with the SJCPHS directive for additional investigation of the lateral and vertical extent of hydrocarbons in the subsurface at the 7500 West Eleventh Street site, the following plan for an extended site characterization program is now proposed. All of the work +- described herein will be performed under the direction of the California-licensed geotechnical engineer who will be in responsible charge of the project. �. 6.1 Extended Topographical Survey The first element of the extended site characterization program will be to extend the topographical survey of the subject property and adjacent areas. That survey will permit inclusion of topographical features to the north of the area that has already been mapped on the site plan that serves as a base for graphical interpretation and presentation of the results of the extended site characterization. (See Figure 2.) Depending upon the topographical features and their relationship to proposed sites for new borings and groundwater-quality monitoring wells, it is expected that the additional area to be surveyed will extend some 600 ft. to the north of West Eleventh Street 6.2 Detection of Underground Utilities To provide safe working conditions, before any site characterization work that involves digging, drilling or probing into the subsurface, the whole of the on-site and off-site areas where such work is to be performed will be surveyed by the United Services Agency (U.S.A.). That agency will mark the locations of gas and water supply pipes, electric lines and other utility infrastructure that is present beneath the surface. On-site detection of buried `~ utilities will be supplemented, as necessary, by a specialist contractor retained by the engineer. .. 6.3 Locations of Additional Groundwater-quality Monitoring Wells ,, The principal objectives of this phase of the extended site characterization, as requested by the SJCPHS, are: to delineate the down-gradient outer limits of the plume of hydrocarbons emanating from the farmer sites of the underground storage tanks and pump islands on the 7500 West Eleventh Street property; to establish the depth to which groundwater has been affected by fuel hydrocarbons in the area close to the former sites of islands at the fueling station's pump islands, which area was the most severely affected by releases of fuel hydrocarbons to the underground; and to explore further the suspected source of a secondary plume of affected groundwater at the southern boundary of the subject property. .� To achieve those objectives, it is proposed to drill one exploratory boring and install the following additional groundwater-quality monitoring wells. SJC