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Addendum to Revised Work Plan for Additional Site Investigation <br /> Former Helena Chemical Facility <br /> January 29,2019 <br /> Page 2 <br /> This Addendum describes three additional step-out borings to delineate the extent of 1,2,3-TCP and nitrate <br /> impacts on the northern boundary of the Site. One boring (1348) will be drilled on Site, northeast of <br /> monitoring well MW-5, along the northern boundary of the property line, and two borings (1349 and B50) <br /> are proposed on the adjacent property to the north(Highland Wholesale Foods).The proposed locations are <br /> presented on Figure 4, attached. Condor anticipates that a monitoring well will also be installed near <br /> proposed boring B48 to delineate the eastern extent of the dissolved 1,2,3-TCP and nitrate-N in <br /> groundwater. <br /> Drilling, sampling, and well installation will follow the procedures documented in the Work Plan. Soil <br /> samples will be collected from approximate depths of 5, 10, 15, and 30 feet below ground surface (bgs) <br /> from each proposed boring and groundwater samples will be collected at depths of approximately 15 and <br /> 30 feet bgs. Soil and groundwater samples will be analyzed for the presence of 1,2,3-TCP and nitrate-N by <br /> the analytical methods cited in the Work Plan. The additional groundwater monitoring well, if warranted, <br /> would be installed approximately 15 to 30 days after the initial borings are drilled and sampled, once <br /> analytical results are available,to evaluate the appropriate placement to delineate the groundwater plumes. <br /> Any additional monitoring well will be constructed as described in the Work Plan. A report summarizing <br /> the drilling activities, results,and recommendations, as appropriate, will be prepared and submitted to the <br /> Central Valley Water Board. <br /> Please contact me at jlaneAcondorearth.com or (209) 938-1061 if you have any questions regarding this <br /> submittal. <br /> Respectfully submitted, <br /> 14AL <br /> CONDOR EARTH ��`°5�,N PC,gcO�p <br /> a. <br /> N0.8795 <br /> OF Gam\Fn <br /> John P. Lane, PG 6795 January 29,2019 <br /> Environmental Services Manager <br /> Attachments: <br /> Figure 1 —Vicinity Map <br /> Figure 2—Site Map Showing Site Features and Sample Locations of Initial Investigations <br /> Figure 3—Site Map Showing Sample Locations 2013 Through 2018 <br /> Figure 4—Proposed Step-Out Boring Locations Based on Recent Groundwater Sampling <br /> cc: Beverly Garcia, Raymond Investments Corporation <br /> Scott Malm,Malm Fagundes LLP <br /> XAPraject\6000_prj\6847 Raymond Investments-Helena Chemical\Reports\Letter Addendum Jan 2019\171,20190129_6847A Addendum.docx <br /> �i� CONDOR <br />