Laserfiche WebLink
STATL OF C;AL�iFORNIA- Environmental Protect jency PETE WILSON, Governor <br /> CALIFORNIA REGIONAL WATER QUALITY CONTROL BOARD <br /> CENT,FAL VALLEY REGION d <br /> 3443 Routier Road, Suite A <br /> Sacramento, CA 95827-3098 <br /> PHONE: (916) 255-3000 <br /> FAX: (916) 255-3015 <br /> 2 October 1996 <br /> Mr. Al McGregor <br /> Operations Manager <br /> Special Environmental Programs <br /> Occidental Chemical Corporation <br /> P.O. Box 728 <br /> Niagara Falls, New York 14302-0728 <br /> PER_ ANENT MONITORING WELL REPLACEMENT WORK PLAN. OCCIDENTAL <br /> CHEMICAL CORPORATION, LATHROP, CALIFORNIA <br /> Thank you for the submittal of the subject work plan. Regional Board staff have reviewed them and <br /> present the following comments which have the concurrence of Mr. Tom Dahl of the United States <br /> Environmental Protection Agency and Mr. Marvin Woods of the California Department of Toxic <br /> Substances Control: <br /> 1. We have no objections with proceeding as proposed for replacement of the monitor wells and <br /> rehabilitation of the extraction wells. However, the attached memorandum presents comments <br /> from the Department of Toxic Substances Control (DTSC) regarding the construction of the <br /> wells. We agree with the DTSC comments and also add that appropriate filter pack materials <br /> need to be selected based on the screen-slot size and the aquifer material characteristics <br /> opposite the screened section. Slot-size should also be so selected. The proposal in the work <br /> plan calls for uniformly using a 60-slot screen and a No. 21 gravel for the filter pack. Given <br /> that the formation being screened is in most cases a sand, a finer slot-size (20- or 30-slot) and <br /> appropriate filter pack is recommended. Justification should be provided for using the <br /> proposed coarser filter pack material and larger slot-size. <br /> 2. As built drawings and specifications of the replacement wells should be provided in the next <br /> available annual/semi-an nuai report following compietion of the weiis. No separaie document <br /> is deemed necessary. <br /> In the future, only one copy of a report needs to be submitted to our office. If you have any <br /> question regarding this matter, please call me at (916) 255-3025. <br /> ALEXANDER MACDONALD <br /> Program Coordinator <br /> cc: Mr. Tom Dahl, U.S. Environmental Protection Agency, Denver <br /> Mr. Marvin Woods, Department of Toxic Substances Control, Sacramento <br /> Mr. Erik Friedrich, Treatek-CRA, Inc., Stockton <br />