Clute/Richwood Waste water Treatment Plant - Executive Summary
The City of Clute/Richwood Waste water treatment plant is required to disinfect the water effluent (discharge) with chlorine as required by permit from both the Federal Environmental Protection Agency (EPA) and the the Texas Natural Resources Conservation Commission (TNRCC) where there is no less than 1 ppm after a 20 minute contact time. The purpose of this process is to prevent pathogens to exit the plant into the surface waters of the State. Further, the permits require that the process must be de-chlorinated where the risudual chlorine does not exceed 0.09 ppm. The dechlorination process uses Sodium Thiosulfate as a safe and environmental friendly process to allow the effluent to be environmentally safe for aquatic life. In Fiscal year 1998-1999, the City of Clute has reconstructed these processes to obtain the permit requirements at an expenditure of approximately $42,000. The results of 100% survival of the Acute and Chronic Bio-Assays, May, 1999, of aquatic life forms in f |
resh and salt water is a positive statement of managements pro-active sensitivety towards the environment and safety. In the last five years there has not been one accident where chlorine gas has left the containment shelter or left the Plant area. Presently, the reconstruction has changed in how the chlorine is processed from what was a pressured manifold to a vacumn system with automatic regulators on the chlorine cylinders.
While the worst case and alternate models indicate a chlorine gas exiting the plant property, does not take into account a unique topographic feature or the fact that chlorine gas has twice the specific gravity of the natural atmosphere. Therefore, it will seek a lower elevation to flow into as water does. Uniquely the waste water treatment plant has flood control channels surrounding it from all four points of the compass. It is bounded on the east with Velasco Flood Control Channnel Number 13 being some 12 feet deep with a 30 foot bottom and side slopes of 1&1/2 to 1with an upper prismodial opening of 66 feet from high bank to the opposite high bank. While the north side of the Plant is presently unoccupied, Velasco Flood Control Channel Number 13 makes a 90 degree bend some 600 feet north of the plant in a westery direction. The plant drains directly into an intermintent channel some 8 foot de
ep and contiguous with both the west plant boundary and the raised ballast of the Northern Pacific mainline railroad some additional 6 feet in elevation. To the south is a heavly wooded section with another Velasco Flood Control Channel of the same dimensions as stated above. Both of the Velasco Flood Control Channels have a common confluence and are about elevation 1.0 and draining east to a pump station 1 and 1/2 miles to the east in the opposite direction from the City through grazing land for livestock ending, at a bottom elevation of minus six. . The worst-case scenario is where the one ton chlorine cylinder effluent valve was damaged allowing the cylinder to vent in 10 minutes at 200 pounds per minute with a wind speed of 1.5 meters per second. The chlorine cyl
inders are enclosed in a vented room to the outside which will passively mitigate 55 percent detention time using EPA's RMP*Comp(TM) model, a toxic endpoint would be 0.9 miles. The prevailing wind direction is from the south by southeast placing the end point to the north at aproximately the intersection of Highway 288 Buisness (Brazoport Blvd.) and Main Street. The model does not take into account that the waste water treatment plant is bounded on the north by heavy to light industrial facilities for metal salvage yard with 12 foot solid perimeter walls and metal fabricateing buildings 40 feet high for the first quarter of a mile. With both the adjoining flood control channels and industrial complex they would passively mitigate the dispersion and affect a population of 60 employees during the work week. Useing the model, the population of residences, a school and a church would require the evacuation of 852 people at the end point as of the last census.
Our Emergency Response Program requires the plant operators to dial 911 or use the hand held or base radio to declare a chlorine leak and evacuate if possible into the prevailing wind. If possible they are to secure with them both SCBA's and the hand held radio to give Emergency Responders and the EOC information as to the direction of the chlorine gas dispersion and vital information for evacuation.
Planned changes as a result of our last safety review, includes connecting the chlorine leak detector to the dialer which will notify the on call waste water plant operater and the City of Clute Police dispatcher of an incident dureing the off hours. Also, a water curtain will be constructed which will be automatically activated by the chlorine leak detector and reduce the exit of chlorine gas by approximately 50% or more from the containment building.