Laserfiche WebLink
to contain less than 10, 000 ppm Total Disolved Solids (TDS) , <br /> which qualified them as Underground Sources of Drinking <br /> Water (USDWs) . <br /> The well was subsequently drilled to the Lower Lathrop mem- <br /> ber of the Panoche Formation where the TDS content exceeds <br /> 20, 000 ppm. According to Federal regulations, 40 CFR <br /> §144 . 3 , this is not considered a USDW. <br /> Comment: <br /> "How do we know that there are not extensive cracks in these <br /> formations which are located at 4 , 350 feet. There is an <br /> earthquake fault in the general area. Could that not become <br /> active and cause cracks?" <br /> Response: <br /> The confining layer will be the Upper Lathrop member of the <br /> Panoche Formation occurring at about 7200-8088 ft. Data <br /> from nearby wells reveals no evidence of faults occurring in <br /> the confining layer within the area of review. Considering <br /> the depth of the confining zone and its thickness, it would <br /> be essentially impossible for a crack or cracks to extend <br /> completely through the confining zone and cause communica- <br /> tion between the injection zone and a USDW. Additionally, <br /> the weight of the overburden layers of sediments would not <br /> allow a crack or cracks to either open up or remain open to <br /> cause communication. Earthquake activity in the area sur- <br /> rounding the CoGen Facility was reviewed and it was deter- <br /> mined that the area has been relatively inactive. The <br /> nearest earthquake epicenter since 1900 A.D. is located ap- <br /> proximately 20 miles away from the CoGen site and was in the <br /> magnitude range of 4 . 0 to 4. 9. This area is historically <br /> considered to be safe from any earthquakes occurring of suf- <br /> ficient magnitude to either cause cracks to form or cause <br /> cracks large enough to cause communication across the con- <br /> fining zone. <br /> 4 <br />