City of Boise- West Boise WWTP - Executive Summary

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West Boise Wastewater Treatment Plant 
RMP Executive Summary 
The West Boise Wastewater Treatment Plant (WWPT) is owned and operated by the City of Boise.  It has been in operation since 1976.  Currently, work is in progress to expand the facility's capacity from 16 mgd to 24 mgd by mid-2000.  As part of the project an ultraviolet (UV) disinfection system is being installed at the West Boise WWTP to replace the chlorine/sulfur dioxide system that is currently being used.  The UV system is expected to be in place and operating by the end of 1999.  At that time the chlorine and sulfur dioxide, the two toxics above the threshold levels in the Risk Management Program on the site, will be removed and the facility will no longer be subject to the Risk Management Program, as found in 40CFR68.112(r). The City of Boise will inform the EPA of the effective date once the changes have been completed and request to be "de-registered". 
The guidance found in EPA's Risk Management Program Guidance for 
Wastewater Treatment Plants, EPA 550-B-98-010, October 1998, was utilized in completing the West Boise WWTP's RMP.  Chapter 4, Offsite Consequence Analysis, provides tables that indicate particular gas release rates and the distance to endpoints related to vessel hole size.  No information regarding the amount released or release duration is required for the release rate calculation in the guidance.  The City of Boise chose to submit the conservative alternative scenerio release rate and endpoint distance information obtained from these tables.  However, Section 3 of the Plan, Alternative Releases, requires input for release amounts and durations of alternative releases.  The release durations were selected to be 10 minutes;  the release duration of the facility's one accident.  The amount released was back-calculated from the release rate and assumed duration.
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