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Geologicaf7echnies Inc. 2601 O txrXpad ren(nplcafand2nyjronmsnle(Spae 'lrp Modute,CR 95351 (209)539.6424 C 2 A j..% March 23,1990 -D LIAR 2 7 ENVIRONMENTAL HEALTH PERMIT/SERVICES Mr.Robert J.Burick Granite Construction Company Heavy Construction Division Box 699 r Watsonville,CA 95077 RE: GROUND WATER MONITORING BC&D PROPERTIES �r I 1129 WI 5T IITbE STfZEET55 ti TRACY,CALIFORNIA -� Dear Mr. Burick: t I have enclosed copies of the two ground water monitoring results performed during the past nine months. Data includes both groundwater gradient and chemical analysis for June 1989 and January 1990. In addition,Geological Technics monitored ground water gradient during other a t periods of 1989 and 1990;that data is also enclosed. Ground water gradient has predominantly been toward the southwest. In July of 1989,the gradient was almost due west. It is difficult to say why the ground water gradient at this site has persisted in a southerly direction, while the regional gradient is to the north. Possible alternatives could be: t 1. A systematic error in measurements and surveying, however, this is unlikely because Geological Technics has had two different personnel perform the task using different methods. 2. The local variation could be caused by leakage from the irrigation pipeline that runs across the northeast portion of the property. It was expected that during the winter months when the pipeline is empty,that gradient would resume a northerly flow. However, this has not been observed. Possibly enough leakage occurs during the summer months to cause a pooling effect which lasts into the winter months. It is noted that a significant amount of leakage was observed in 1987 during the drilling process. Evidence for this is that during the drilling of soil boring 5(just south of the pipeline near the center of the property),water came up into the hollow stem auger. The duration of this 1