SITE INFORMATION AND CORRESPONDENCE

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Mike Vivas, P.E. City of Lodi's City Hall Annex May 17, 2002 Page 2 of 4 GENERAL COMMENT The highest level recorded so far was 960 micrograms/cubic meter of PCE (November 2001). Allowable risk (cancer and non-cancer), potency slope and hazard indices should be identified for all chemicals of concern in order to identify the maximum concentrations of contaminants allowed in the indoor air. Examples of allowable risk are expressed in terms of 1 in a million (1 X 10-6), 1 in one hundred thousand (1 x 10-5), etc. WHAT IS THE MAXIMUM CONCENTRATION OF PCE ALLOWED IN INDOOR AIR? Due to the lack of a defined allowable risk, potency slope factors, and hazard indices, ESU is unable to evaluate and determine how much additional fresh air should be added, or whether additional treatment units should be used on site at this time. EVALUATION OF HVAC MODIFICATIONS AND COMPLIANCE WITH TITLE 24 There are some additional issues that require to be specified to further evaluate what the ambient air maximum concentration should be. A mass balance of each contaminant in the air would be useful in determining the minimum fresh air rate. On February 19, 2002, 1 had the opportunity to see the facility and be present when the Heating, Ventilation, and Air Conditioning (HVAC) modifications were proposed (increase outside air through the HVAC economizer for the South unit and modifying the East and West units to increase fresh air intake). Based upon our conversations with Magellan Environmental Inc. at that time it was understood that the HVAC system (circulation fans) would operate 24 hours/day. It is our understanding that these modifications have been instituted except that the HVAC system is shut down at night. ESU requests information and calculations (flow analysis of the HVAC systems to determine the total volumes of air flow and fresh air input, total air exchange rates, etc.) be provided. It will assist us in determining: a). mass balance of air and contaminant levels; b). that Title 24 requirements are being met; and c). the need for modification(s) to the pre-modification maintenance schedule(s). ESU recommends that the following air parameters be collected and reported: 1 . the indoor and outside ambient air temperature (on an hourly basis), 2. relative humidity (both indoor and outside ambient on an hourly basis), 3. prevalent wind direction and velocity (continuously), 4. flow velocity of each supplied air, return air, and exhaust air ducts (on an hourly basis),