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' California P Department of Transportation Revised September 23, 1994 P P Project No. 102818-01 Ninyo & Moore used Environmental Assessors, Inc Figure 1 (Location of Soil Bonngs and ' Monitoring Wells) to draft the monitoring well locations to create the groundwater gradient map The top of casing elevations used to create the groundwater gradient map were obtained from two previous reports (Alton Geoscience, 1992, and Environmental Assessors, Inc, 1994). No documentation was available as to whether or not the land surveys were conducted by a State of California licensed surveyor. The text of the Alton Geoscience and Environmental Assessor,Inc reports do not indicate the location of the benchmark used for the land survey, however, on Figure 1 of the Environmental Assessors, Inc. report shows a benchmark located northeast of the site lust east of South B Street It is not known whether all monitoring wells were surveyed to the same benchmark Furthermore, it is not known whether monitoring wells MW-1 through MW-12 were located by surveying or by approximation Apparently,morutonng wells MW-13,MW-14,MW-16,MW-19,MW-20, and MW-24 were surveyed to a grid system of northing and easting (Environmental Assessors, Inc, 1994, Table 2 - Survey Data for Wells) Based on the information supplied, it appears that the monitoring wells were not surveyed by a State of Califorrua licensed surveyor A summary of well construction details (Environmental Assessors, Inc., 1994, Table 4) reviewed by Ninyo & Moore indicates that the screened interval for monitoring wells MW-13,MW-14, MW-19, and MW-20 starts at approximately 65 feet, and MW-16 starts at 66 feet The depth to groundwater at monitoring well MW-13 was 64 79 feet below top of casing, therefore monitoring well MW-13 is apparently not screened through the groundwater surface and the depth to groundwater may not be representative of site conditions The depth to groundwater at monitoring well MW-16 was 65 58 feet below top of casing, therefore monitoring well MW-16 is apparently not screened through the groundwater surface and the depth to groundwater may not be representative of site conditions. The depth to groundwater was 65 60 at monitoring well MW-14, 65 50 at monitoring wells MW-19 and MW-20 The approximate top six inches of a typical threaded well screen is blank well casing, therefore, monitoring wells MW-14, MW-19, MW-20 may also not be screened through the groundwater surface and accordingly the depth to groundwater may not be representative of site conditions i 3 �dGI�Cm��®®PCS