FIELD DOCUMENTS_CASE 1 - Laserfiche WebLink

Home Browse Search

Monitoring Well Destruction and Soil and Groundwater Investigation Report US Can—Welty Road December 28,2010 First-encountered groundwater depths ranged from 32 to 39 feet bgs. Static groundwater-level measurements at each borehole indicated that groundwater stabilized between 33 and 37.4 feet bgs. Therefore,based on soil moisture observations and static water-level measurements, the groundwater appeared to occur under unconfined conditions. SAIC-Benham collected groundwater samples from all borings and submitted the samples for analysis of the HPP-BTR constituents. The groundwater sample collected from SB-44 was also analyzed for General Minerals and Total Dissolved Solids (TDS)to evaluate the suitability of the uppermost groundwater for drinking-water use. The boring logs, which describe USCS soil classifications,photoionization detector(PID) readings, and observations of hydrocarbon-affected soil and/or groundwater, are provided as a component of Appendix D. Boring locations were surveyed for longitude and latitude coordinates within a 5-foot range using a Global Positioning System(GPS)with reference to the World Geodetic System 1984 coordinate system and datum. 4. ANALYSES 4.1 ANALYTICAL RESULTS AND DATA USABLITY SUMMARY Analytical methods used for samples collected at HPP-BTR sites are provided as a component of Appendix E. Soil analytical results, RSLs, and ESLs for the HPP-BTR constituents are summarized in Tables 1 and 2. Soil analytical results and the extent of affected soil are shown on Figure 3. The groundwater analytical results,ESLs, and WQOs are summarized in Tables 3 and 4; WQOs and California Department of Public Health(CDPH)maximum contaminant levels (MCLs; CDPH, 2010)are summarized in Table 5. A map showing the distribution of the dissolved HPP-BTR constituents in groundwater is provided on Figure 3. SAIC-Benham performed a data usability evaluation to determine whether the data could be used for the intended purposes (i.e., delineation,risk evaluation,remediation). The evaluation determined that all analytical data are usable. The data usability summary is provided as Appendix F. Qualified data with reason codes are provided in Tables 1 through 4, and summarized in Appendix F, Table F.1. 5. DISCUSSION 5.1 EXTENT OF AFFECTED SOIL AND GROUNDWATER Soil analytical results were compared to the lowest, most-conservative RSL and ESL values for delineation purposes. Three distinct areas of affected soil(Areas 1 through 3)have been noted based on groups of contiguous borings with HPP-BTR constituents at levels above RSLs and ESLs. With the exception of two detections of naphthalene in excess of the RSL(SB-46 at 38 feet bgs and SB-47 at 34.5 feet bgs), all soil results were below screening levels. The extent of crude-oil affected soil is delineated on Figure 3. Groundwater analytical results were compared to the lowest, most conservative ESL and interpreted narrative WQO values for delineation purposes. An area of affected groundwater was noted based on groups of contiguous borings containing separate-phase oil(SPO) or with HPP-BTR constituents detected at levels above WQOs/ESLs. The estimated extent of crude-oil affected groundwater is shown on Figure 3. The area of affected groundwater has been delineated to the west, south,and east. Affected groundwater 44117 The Benham Companies,LLC A Wholly ly Owne0--J$ubs�diniy From Science to Solutions