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' Diamond Lumber-Lodi Quarterly Groundwater Monitoring Page 4 elevation control for at least three points that lie on a common plane, in this case the groundwater surface. The elevation control was obtained by subtracting the static water levels (measured from the top of well casings) from the elevations of the well heads (referenced to the City of Lodi Bench-Mark 710: 49.74 feet). It should be noted that the groundwater elevations varied by only a few tenths of feet. Based on calculations using data during the February sampling event, the groundwater has a very slight gradient in a southerly direction. It should be noted that the groundwater gradient is extremely flat (the difference in static groundwater elevations between the highest and lowest point, 140 feet laterally is approximately 0.15 feet. Copies of the hand calculations and cross-sections used in determining the groundwater gradient are provided in Appendix B. 4.0 GROUNDWATER SAMPLING Three casing volumes were purged from each of the SRK monitoring wells using dedicated disposable bailers equipped with nylon cord. The purged casing volumes were measured in a calibrated bucket, then emptied collectively into a 55-gallon drum located near SRK-MW2. The drum lid was securely fastened after the three wells were sampled. After more than 3 casing volumes were purged from each well, the analytical groundwater samples were collected from the tops of the dedicated teflon bailers- Analytical water samples were preserved in laboratory grade sampling containers. The analytical groundwater samples were placed in a cooler containing additional frozen blue ice packets and shipped following strict chain-of-custody procedures to a California certified laboratory (ACZ Laboratories) for analysis. These samples were collected after the Ph, temperature and conductivity had stabilized. "Stabilized" is defined as three consecutive readings within 15% of one another. Copies of the Geologic Logs and Monitoring Well construction Diagrams are provided in Appendix C. Copies of the purging/sampling logs are provided in Appendix D. The analytical parameters include volatile hydrocarbons (by EPA 8015M, GC/FID Purge & Trap), benzene, toluene, ethylbenzene, and xylene (BTEX) (Aromatics by EPA 602/8020, GC/FID Purge & Trap); and total lead (EPA Method 239.2 GFAA). ' Ethylenebromide ({EDB) was not included in the suite of analytes, because EDB degrades in soil very rapidly (EDB is c.`3iverted il.,,.^,St c^.^.:pletely within42 .^.i.,ntlis to etl:y:.a.^.e) CA— 315.". in water, where ' it hydrolyzes to ethyleneglycol and bromoethanol (under neutral conditions and ambient temperature the half-life of the reaction is 5-10 days). 5.0 ANALYTICAL DATA Organic and inorganic analyses were performed by ACZ Laboratories (CA Lab #E608). Copies of the analytical data and chain-of-custody are provided in Appendix E. The chain-of-custody clearly documents that the samples were shipped from California to Colorado and also indicates Sample Steffen Robertson and Kirsten 32 .21\4.QW V A0d