Laserfiche WebLink
0 0 <br /> C A M B R I A AMeVId UAlP4-Y, February 2,2007 <br /> Mr. Timothy R. O'Brien, PG,CEG,CHG auzco t*44-a � <br /> Regional Water Quality Control Board ►(�(v'• d. <br /> Central Valley Region • Y-Wsect c7t C plC',n. <br /> 11020 Sun Center Drive, Suite 200 o W�lh l <br /> Rancho Cordova, California 95670 <br /> Re: Soil Investigation and Background Groundwater Monitoring Well Installation <br /> Workplan Addendum <br /> Camanche Dam Powerhouse <br /> 23900 E. Buena Vista Road <br /> Clements, San Joaquin County, California <br /> ® Dear Mr. O'Brien: <br /> On behalf of East Bay Municipal Utility District(the District),Cambria Environmental Technology, <br /> Inc. (Cambria)has prepared this addendum to the Soil Investigation and Background Groundwater <br /> Monitoring Well Installation Workplan (the workplan) dated January 17, 2007 in response to the- <br /> Regional Water Quality Control Board's (RWQCB) conditional approval letter dated January 30, <br /> 2007 (Attachment A).Presented below is the additional information requested by the RWQCB. <br /> 1. As stated on page 4, paragraph 2 of the workplan, Cambria inferred the groundwater flow <br /> direction and depth based on local topography,and the elevation of the Mokelumne River.At this <br /> time,this is our interpretation of the limited data we have available.After the monitoring wells are <br /> installed and developed we will have data to determine the groundwater flow direction and if the <br /> Mokelumne River is a gaining or losing stream. The wells have been proposed in a triangular <br /> configuration to anticipate either flow direction. <br /> 2. Currently,we only have site specific data for the top 6.5-feet of sediments.However,the site is <br /> located in the flood plan of a major stream and we suspect at depth that we will encounter coarser <br /> stream channel deposits that will require a drilling method that can advance through cobbles and <br /> boulders. Therefore, we propose using the ODEX Casing system, which advances the casing <br /> simultaneously with the air-rotary hammer. Soil samples will be collected with an 18-inch <br /> California Modified Split Spoon Sampler lined with stainless steel liners in advance of the casing <br /> and air rotary hammer. <br /> 3. As shown in Figure 1,we propose to construct the bottom of the monitoring wells with a threaded <br /> Cambria <br /> Environmental 4-inch diameter polyvinyl chloride(PVC)well cap. <br /> Technology,Inc. <br /> 5900 Hollis Street <br /> Suite A <br /> Emeryville,CA 94608 <br /> Tel(510)420-0700 <br /> Fax(510)420-9170 <br />