Jacob Hands Wastewater Treatment Facility - Executive Summary

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The City of Las Cruces owns and operates the Jacob Hands Wastewater Treatment Facility (JHWWTF) through the Department of Water Resources.  This facility has a design capacity of 8.9 million gallons/day.  During the treatment process, chlorine gas is used to disinfect treated wastewater to protect human health, and is followed by sulfur dioxide gas to dechlorinate the treated wastewater before it is discharged to the Rio Grande.  Treatment with sulfur dioxide removes residual chlorine in the last step, so the treated wastewater will not harm aquatic organisms or wildlife in the river. 
 
The gases, liquified under pressure, are delivered to the JHWWTF in 1 ton containers to a single receiving and storage facility specifically designed for these operations.  The facility is equipped with area gas detectors and alarms.  The amount of gas used in both processes is enough to require multiple 1 ton containers.  Three containers are connected to separate, state-of-art vacuum regulator-manifol 
d assemblies for each process.  Because these are toxic gases, special features for safety and reliability have been built into the design of these systems.  The regulators are attached directly to the valve on each container.  When in service, the vacuum applied to the regulator pulls a spring mechanism that opens the valve on the container.   If something fails or leaks, the reduction or loss of vacuum enables the spring to close the valve automatically.  Thus, the system fails to a safe condition.   
 
The hazard prevention policy of the Department is to combine state-of-art engineering controls that are reliable, practical, and cost-effective with pro-active, diligent management to operate and maintain both systems at the highest level of safety and performance.  Operators are certified, and trained on site and through a statewide program of continuing education.  Both systems were upgraded in 1995 from their original design to remain current with technological advances.  The mainten 
ance system is fully integrated within the computerized operations system for JHWWTF.  Further, the JHWWTF has been in compliance with the requirements of OSHA's Process Safety Management. 
 
The Department's incident/emergency response policy is to set well-defined limits on operator exposure and responsibility with direct linkage to our Local Community Emergency Response Team.  When a situation exceeds Level 1 criteria, professional emergency/haz-mat responders are notified immediately to deal with the potentially dangerous situation.  The response of JHWWTF staff is limited to those situations that may occur during normal operations, and for which they are trained and sufficiently experienced, i.e. minor leaks that may occur during the connection or replacement of containers.  Operators wear a self-contained breathing apparatus and a Repair Kit B stands by during these operations.  Any incident that exceeds minor leaks during routine connecting or disconnecting of regulators to contai 
ners (Level 1) is immediately referred to the Las Cruces Fire and Emergency Services (911) and triggers the Local Community Emergency Response through the NM State Police.  Fire Department units from Station 3 can arrive within 5 minutes, and would be followed immediately by units of the Fire Department's Haz-Mat Response Team from Station 4.   In such an incident (Levels 2 and 3), JHWWTF staff would notify contact persons at neighboring facilities, and then evacuate the site until the situation has been stabilized and authority has been returned to the JHWWTF Manager. 
 
Prudent precautions are taken during operations, and are undertaken only when sufficient supporting staff are present.  Connection and replacement of containers is done only during the day shift.  JHWWTF staff conduct training and periodic meetings with the Haz-Mat Response Team to ensure that the entire emergency response is as seamless as possible.  Limited emergency response exercises have been done in the past.  We  
plan to conduct a chlorine gas scenario in the near future.  To date we have had no incidents involving chlorine or sulfur dioxide. 
 
We have followed EPA guidance, Risk Management Program Guidance for Wastewater Treatment Plants (40 CFR Part 68), EPA 550-B-98-010 (October 1998), while preparing this RMP, and for the analyses of off-site consequences of toxic gas releases.  All scenarios were analyzed using table values from the guidance.  The worst-case analysis was done for chlorine gas released at 200 lb/min from a container containing 2000 lbs over a period of 10 minutes under default conditions.  This analysis indicated the distance to the endpoint concentration at 1.3 miles.  Because we have had no incidents, and because the facility and gas delivery systems have engineered safety features, the only reasonable, although unlikely, scenario we could imagine for an alternative scenario was the shearing-off or loss of the valve/regulator assembly.  Such an event could create a > inch  
hole above the liquid level in the container.  The analysis of a vapor release scenario for both toxic gases under default conditions indicated the distance to the endpoint concentration at 0.2 miles when table values were applied.  
 
There are a wide variety of public receptors within a radius of 1.3 miles.  In the worst-case release scenario, the NM State Police would initiate the Local Community Emergency Response and organize notification, evacuation (or protection in place), and control of the appropriate area.  In both alternative scenarios, only adjacent facilities would be affected, as most of the area around the gas receiving and storage area is pecan orchards or open fields.  Interstate Highway 10 could be affected in a release but it is elevated about 30 ft above the JHWWTF and, depending on conditions, it might remain above the top of a denser-than-air gas plume.  As such, the embankment of the interstate highway would serve as a dike for the area to the south of the JHWWTF. 
 
 
Planned changes to improve safety include actions recommended by the consulting engineers that performed an independent audit of the facility as part of our preparation of the RMP.  The consultant found only a few minor improvements that needed to be done: a) additional and more prominent warning signs and placarding at the container receiving and storage area, b) better labeling of valves and piping to indicate direction of flow and turning of valves for the chlorine and sulfur dioxide systems, c) increased barricading at the receiving and storage area to minimize the potential for vehicular accidents with the containers or system equipment, and d) added procedures or documentation needed to meet specific RMP requirements.  These items have been addressed in completion of the RMP for submission by 21 June 1999.
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