SITE INFORMATION AND CORRESPONDENCE

Home Browse Search

t1Ub6Ub-J34 LUn-Lo being the first that were completed. A summary of the various investigators who have worked at the Depot and the sampling activities have been discussed in Sections 1.0 and 2.0 of this report. 4.3.1.2 The following sections characterize groundwater quality on the Depot and in the vicinity: These sections are: (1) the natural groundwater quality in the vicinity of the Depot, (2) the results of nearby private well sampling, (3) a discussion of the Radian investigation, (4) a discussion of the WCC investigation, and (5) a summary of the extent of groundwater contamination. 4.3.2 Natural Groundwater Quality 4.3.2.1 Introduction 4.3.2.1.1 As discussed in Section 3.6.3, the uppermost aquifer underlying the Depot is a hydrostratigraphic unit (HSU) known as the Upper Tulare Formation. This HSU extends to a depth of approximately 200 feet, and is underlain by approximately 80-120 feet of the Corcoran Clay, which acts as a regional aquitard to confine groundwater in the lower section of the Tulare Formation. All of the monitoring wells constructed as part of the investigation at the Depot are completed in the Upper Tulare HSU. 4.3.2.2 Potability 4.3.2.2.1 Previous investigations by Hotchkiss and Balding (1971) have characterized the groundwater quality in the Upper Tulare HSU as generally saline with elevated concentrations of nitrate, fluoride, iron, and boron. The low number of off-Depot wells sampled by WCC (15 private wells) , and incomplete information regarding well construction, do not allow for a rigorous statistical calculation of background values for chemical parameters tested. However, to evaluate the natural water quality, chemical results of groundwater sampled from selected private wells have been evaluated. 4.3.2.2.2 To characterize the natural groundwater quality, the chemical results of groundwater samples collected by WCC in 1987 from nine upgradient and cross-gradient wells located within 1 mile of the Depot were 4-160