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Mrs. Beverly Garcia - 2 - 27 November 2018
<br /> In groundwater, 1,2,3-TCP was detected above its maximum contaminant level (MCL) of 0.005
<br /> micrograms per liter (ug/L) in borings B42, B43, B44, and B45, advanced near the northern
<br /> property boundary where 1,2,3-TCP was previously detected at 12 ug/L during the May 2016
<br /> investigation. 1,2,3-TCP was detected in B42 at 16 ug/L(15 feet bgs) and 0.036 ug/L (30 feet
<br /> bgs); B43 at 0.034 ug/L (15 feet bgs) and 0.01 ug/L (30 feet bgs); B44 at 11 ug/L (15 feet bgs);
<br /> and B45 at 0.078 ug/L (15 feet bgs). 1,2,3-TCP was not detected in groundwater samples
<br /> collected from the monitoring wells (MW-1 through MW-5). 1,2,3-TCP was also not detected in
<br /> any of the soil samples collected.
<br /> Nitrate (as nitrogen) was detected above its MCL of 10 milligrams per liter (mg/L) in grab
<br /> groundwater samples from boring B42 (210 mg/L at 15 feet bgs); B43 (230 mg/L at 15 feet bgs
<br /> and 26 mg/L at 30 feet bgs); B44 (230 mg/L at 15 feet bgs); B45 (200 mg/L at 15 feet bgs); and
<br /> B47 (68 mg/L at 23 feet bgs). Nitrate was also detected above its MCL in monitoring wells
<br /> MW-1 (240 mg/L), MW-2 (290 mg/L), and MW-3 (70 mg/L). Up to 93 milligrams per kilogram
<br /> (mg/kg) of nitrate as nitrogen was detected in soil.
<br /> Based on the June 2018 investigation results, 1,2,3-TCP in groundwater is not defined to the
<br /> north, east, northeast, and northwest of the area where borings B42, B43, B44, and B45 were
<br /> advanced. Similarly, nitrate in groundwater is not defined to the north, east, northeast, and
<br /> northwest of the area where borings B42, B43, B44, and B45 were advanced. Step-out borings
<br /> are necessary to fully define the lateral and vertical extent of 1,2,3-TCP and nitrate to the north,
<br /> east, northeast, and northwest of borings B42, B43, B44, and B45.
<br /> By 28 December 2018, please submit proposed locations and depths of step-out borings to fully
<br /> define the lateral and vertical extent of 1,2,3-TCP and nitrate at the Site as an addendum to the
<br /> approved 27 February 2018 Revised Work Plan for Additional Site Investigation.
<br /> If you have any questions regarding this letter, you can contact me at (916) 464-4746, or by
<br /> email at Aimee.Phiri@waterboards.ca.gov.
<br /> AIMEE C. PHIRI, P.E.
<br /> Water Resource Control Engineer
<br /> Federal/Private Site Cleanup Unit
<br /> cc (by email): Mr. Scott Malm, Malm Fagundes LLP, Stockton
<br /> Mr. John Lane, P.G., Condor Earth Technologies, Inc., Stockton
<br /> Alex Dewitt, P.G., Condor Earth Technologies, Inc., Stockton
<br /> Michael Kith, San Joaquin County, Environmental Health Department
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