SITE INFORMATION AND CORRESPONDENCE_FILE 2

Home Browse Search

Mr. Jack Badey - 2 - 30 June 2009 constructed on parallel subslab grade beams, with 30-foot wide. 130-foot long gravel-filled channels between the beams. The test results show that a low pressure vacuum system withdrawing vapors from an extraction port can be expected to have an effect up to about 70 to 80 feet away. This distance appears to be enough to prevent vapors from collecting beneath the floor, thereby preventing their migration into the indoor air space. Three extraction ports are proposed, one in each of three adjacent channels. Two channels contained exceedances of PCE in subslab samples and correlate with the location of the indoor air samples exceeding the CHSSL threshold. The third channel was not sampled, but due to its proximity, is assumed to contain excess PCE vapors. Unifirst will work with the San Joaquin Valley Air Pollution Control District to permit the system, determine if treatment is required, and establish an appropriate monitoring schedule. Central Valley Water Board staff conditionally concur with the sub slab depressurization work plan, conditioned on Unifirst meeting San Joaquin Valley Air Pollution Control District requirements. By 30 October 2009, please provide California Regional Water Quality Control Board, Central Valley Region, (Central Valley Water Board) with either a copy of the Air Pollution Control District Permit, or a status report on the progress, and by 30 December 2009, provide a sub slab depressurization installation report, including an updated schedule of air monitoring analyses and a proposed schedule to transmit the air monitoring data to Central Valley Water Board staff. If you have any questions, you may contact me by telephone at (916) 464-4680, or by email at aterrell waterboards.ca.gov. AMY TERRELL Private Sites Cleanup Unit cc' Mr. Michael Infurna, San Joaquin County Environmental Health Department, Stockton Mr. William Pipes, AMEC Geomatrix Inc., Fresno