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California --egional Water Quality Con A Hoard <br /> -Ya <br /> Central Vallev Region <br /> Karl E. Longlev,ScD. N.F..('hair <br /> Linda S.Adams 11020 Sun Centcr Drive#200,Rancho Cordova,California 95670-6114 Arnold <br /> Secre7aryfor M arzenegger <br /> Phone(916)464-3291 •FAX(916)464-4645 (] _ 21117vironn7ental ,-1El bPro7ecnan http://www.waterboards.ca.gov/centrahalle% J��Lffl <br /> JUL 0 2 2009 <br /> ENVIRONMENT HEALTH <br /> 30 June 2009 <br /> PERMIT/SERVICES <br /> Mr. Jack Badey <br /> ENS Manager, UniFirst Corporation <br /> 68 Jonspin Road <br /> Wilmington, MA 01887 <br /> REVIEW OF INDOOR AIR SAMPLES AND SUB-SLAB DEPRESSURIZATION WORK <br /> PLAN , UNIFIRST, 819 HUNTER STREET, STOCKTON, SAN JOAQUIN COUNTY <br /> Unifirst operates a wet-wash laundry facility adjacent to the location of a former dry-cleaning <br /> facility. In October 2007, Unifirst detected perchloroethene (PCE) in soil gas samples <br /> obtained from beneath the parking area near the former Parisian Laundry facility. In <br /> December 2007, Unifirst obtained soil gas samples beneath the Unifirst building. and in <br /> December 2008, Unifirst obtained air samples from within the Unifirst building. The results of <br /> the interior air samples, and a proposal to prevent continued movement of PCE from the <br /> subsurface to indoor air are contained in the following documents prepared by Unifirst's <br /> consultant, AMEC Geomatrix. <br /> • 6 February 2009 Limited Indoor Air Quality Assessment Report <br /> • 20 May 2009 Results of Sub-Slab Depressurization Testing <br /> As reported in the Limited Indoor Air Quality Assessment Report, the indoor air samples were <br /> obtained from the dry portion of the building, where the potential for volatile contributions <br /> from dirty laundry would be expected to be minimal. The indoor air contained about 12 ug/m3 <br /> of PCE, which is below the permissible exposure limit of 170,000 ug/m3 established by the <br /> Occupational Safety and Health Administration (OSHA), but above the California Human <br /> Health Screening Levels (CHHSLs) established by the California Office of Environmental <br /> Health Hazard Assessment. <br /> In order to remove vapors from the indoor air space, Unifirst proposes to apply vacuum <br /> pressure beneath the building to remove vapors and route them to a treatment system, if <br /> needed. In the Results of Sub-Slab Depressurization Testing report, Unifirst reports on <br /> preliminary tests it conducted to obtain design parameters for the vapor removal system, and <br /> presents the resulting work plan for vapor removal. <br /> Sub-Slab Depressurization <br /> Unifirst conducted a series of vacuum tests beneath the building where the highest <br /> concentrations of PCE were found in subslab and interior air samples. The building is <br /> California Environmental Protection Agenc3, <br /> Rerrcled Pn/Irr <br />