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�a L i" KLE I NFELDER August 8, 1988 V"� �� `� ►a �� File: 24-1132-20 AUG G 1988 Mr. David Carls San Joaquin Local Health District VIR��ENTAL HEALTH P.O. Box 2009RMty/sworES. Stockton, CA 95201 RE: Response to Comments Made on the Jordan Real Estate Proposal Dear Dave: Inres onse to the comments you made during our August 3, 1988, telephone conversation regar ing the Jordan Real Estate Proposal, I am submitting this letter which addresses your concerns. 1. EDB Sampling - Since earlier sampling detected no EDBs and EDBs are listed as an optional parameter for soil sampling in the June 2, 1988, document Regional Board Staff Recommendations for Initial Evaluation and Investigation of Underground Tanks,"we do not feel that comprehensive EDB sampling is necessary. In response to your request that we test for EDBs, we propose to test the water samples from the two downgradient wells for EDBs. f� 2. High Moisture Content - Appendix A, Kleinfelder Field Procedures, is a + general description of field procedures used by Kleinfelder staff. Since this is a general description, not all of the techniques listed will necessarily be used in every investigation. Using high moisture content as a criteria for selecting soil samples will not be employed at the Jordan site. This technique is useful in situations where there is liquid migration from a landfill or surface impoundment. 3. Well Development and Samplingg - You were concerned that we proposed to pull samples from the wells 24 to 48 hours after development. You mentioned that Gary Johnson at the Regional Water Ouality Control Board recommended that two weeks elapse between well development and sampling. Monitoring wells are developed to remove an material that may hinder the free flow of ground water into the well lumen. Durin development, pressure waves are used to dislodge the blocking materia These pressure waves may affect the concentration of volatile organics and; therefore, the volume of water affected by these waves cannot be used for sampling. In his book "Ground Water and Wells," F.G. Driscoll states that filter packs for wells should be no thicker than 8 inches because the strong pressure waves generated during development do not travel much further than 8 inches. If we conservatively assume that the ground water within a 1 foot radius of the well is affected by the pressure waves and cannot be used for sampling, we can look at how that volume of water can be avoided.