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FEB 26 •97 14:06 FROM • TO 12094433 PAGE. 004z011 :ta v L-Atennedy/Jenkg Consuftamb C y „" Engineers and ScierrItists tlnw?ONME::TAL HEAUH M 30J Sec-x=SUM 28 August 1991 Sin kw1Com Cakbrr� 94107 415-24.&}2150 FAX s15M&6o9" Mr. Michael Wiggins Regional Water Quality Control Board 3443 Routier Road, Suite A Sacramento, Cahfomia 95827-3098 Suhiect: Lincoln Village Center Well Destruction Proposal K/J 900109.40 Dear Mr. Wiggins: Thank you for the opportunity to review the destruction proposal for San Joaquin Couunty (Lincoln Village Maintenance District) wells Number 1, 2, 4, and 6. As you are aware:. wells 1, 2, and 6 penetrate through the contaminated water bearing Zone 'A' at Linc=oln Village Center (LVC). Therefore, it is important that these wells are properly desttoyeed to �. minimize the possibOiity that they will act as conduits for the vertical migration of volattae Organic compounds (VOCs). Based on our preliminary review, we have a number of concerns regarding the adequacy of the proposed well destructions to provide protectmon against the vertical migration of VOCs to the lower water booting zoites. M general it should be rioted that the recommendations of the current proposal does root appear to address the $pacific hthology in the area. We behove that at a minimum, it ,will be necessary to puncture the blank casing and pressure grout the wap throughout the. depths corresponding to suspected aquitards, therefore creating an adequate seal withhin the formation. Basad upon our pthologic evaluation of the area, we have defined a Zcane "C' aquifer from a depth of appro>omately 180 to 260 feet. A well-defined aquitard apparenity exists from a depth of 140 to 180 feet. AN well casings should be puncttured or ripped and the formation pressure grouted throughout this zone. The remaining lithology consists of thinner clay and sand zones. Because of this, we would recommeend that casing from 40 to 180 feet be punctured and pressure grouted to provide protecWon for intermediate water bearing zones. Based upon this evaluation, we would like to recommend the following changes to the proposed destruction of each well. Wells 1 and 9 It appears that walls number 1 and 2 have been mislabeled. Based upon our recent videotapes, wap number 1 is open to a depth of approximately 187 feet, below which' the well is filled with sediments. The casing is perforated from a depth of 164 feet to then bottom of the well. Well number 2 showed no evidence of cave-in, and was open to as depth of approximately 275 feet. Perforations were located from a depth of 212 to 2;52 • feet. Both of these wells should be destroyed as previously discussed. G;00014