SITE INFORMATION AND CORRESPONDENCE FILE 2

Home Browse Search

Rodger Liston Darpetro Inc. 749 E. Charter Way, Stockton, California Page 4 of 5 Local and regional plan view maps with sources , boring and monitoring well locations, lines of cross section , extent of contaminants in each media , direction and rate of ground water flow, and receptor locations , including water supply wells within 2 ,000 feet of the site . Cross sections showing subsurface geological features, depth to ground water, man�made o ion and an interpretative drawing of the vertical extent V olf soil n and tground water contamination . l concentrations vs . time for representative Cross-plots of key chemica wells that demonstrate significant contaminant concentration trends . Summary tables of contaminant concentrations in the different media. Well and boring logs . e SCM that describes controls on contaminant A narrative description of th plutmeutdispostonmover ttime;raand otion erbednland dissolvedsmso srates; masses. While not necessarily showing all data in diagrams and drawings , an adequate SCM can be utilized to account for most of the known data and to illustrate additional assessment needs . All analytical data should be included in tables. Methods and calculations of contaminant masses should be included in the SCM , and may be submitted as an appendix. The site conceptual model should be updated each time new data is acquired that causes a change of interpretation or expands the model until model modifications are not needed to explain subsequently acquired data . As the SCM becomes complete, it can be utilized to reasonably predict additional investigation results and plume response to various remedial technologies or to changes in ground water flow regime . The model should adequately demonstrate all interpretations and opinions . E by EHD- noted during this review that if the dates a first etection of earliest detections will Method 8260M in each well are mapped that include wells BM- 1 , BM-3 and BM-5 ; the remaining first detection dates can be contoured by year with progressively later first detection dates further away from r the `core' . A similar map can be produced by mapping highest TBE concentrations detected by well , though the 'core' shifts a bit to include wells BMA , BM-3 and BM-4 , and the 28 µg/I detected in BM-9 exceeds the 3 .4 µg/l detected in BM-7 . These maps suggest to EHD that there may be a minor plume fringe migrating toward the southeast from the 701 E . Charter Way site that MTBE ' impacts BM-7 and BM-91 but that the core' centered on BM-1 , BM-3 , BM-4 and BM-5 are related to a release on the 749 E . Charter Way site . This is some data that perhaps should be more carefully evaluated and incorporated into your site-specific SCM to resolve the various issues related to the site. These observations should certainly be explainable by your revised SCM .