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Corrective Action Plan Page 26 treated at an one time is very much smaller than one cubic yard and thus falls within the Y rY permit exemption limits for uncontrolled soil aeration set by the SJVUAPCD (Ref 4) If any very fine colloidal or other suspended matter passes through the primary filtration system it is trapped by a secondary, in-line, bag-type filter (System 14 on Figure 10) installed in the influent line to the air-stripper This unit is maintained manually, as required, by removing and cleaning or replacing the filter bag Surge-Tank To balance the flow to the air stripper and accommodate intermittent operation of the groundwater recovery pumps, after passing through the primary filtration system, the pumped groundwater passes into a 1000-gallon, surge tank (System 12 on ` Figure 10) The water level in this vessel is moderated by an array of high-level and low- level sensors and controls that regulate the pump that discharges water from it and also regulate the groundwater pumps so that the discharge pump will not run dry and the tank will not be overtopped Noise Control With the exception of the air stripper, all of the groundwater treatment equipment operates silently, or generates insignificant noise such as that produced by low-power electric pumps The un-silenced, high-capacity blower that forces air through the stnper generates noise at around 87 decibels (dB) To control this sound, the unit is fitted with a silencer and is housed in a noise-control enclosure (System 5 on Figure 10) n supported The noise-control enclosure is constructed from modular acoustical panels pp orted b y a galvanized steel frame The 4-in thick, non-combustible, fire retarding, acoustical panels are designed to produce a sound transmission loss of at least 30 decibels between the interior and exterior of the enclosure They are be fabricated with a 16 gauge, galvenized- bondenzed cold-rolled steel inner and outer skins that sandwich a filling of inert, mildew and vermin resistant acoustical insulating All penetrations through the walls for pipes conduits and ducts are sealed with acoustical insulating material supplied by the panel manufacturer Full-width, full-height doors at one end of the noise-control enclosure provides access for inspection and maintenance of the air stripper The interior of the enclosure is ventilated by a forced-air fan When the air stripper is operating, the doors of the noise-control enclosure are closed Under these conditions, noise levels at the surrounding fence line will be about 52 dB decibels, which complies with the 55 dB property-line, hmrt set for residential areas by r City of Tracy Ordinance No 898 C S and is very much less than the 65 dB permissible in commercial districts such as that where this subject site is located (Ref 2) J r