FDEP Reports on Toxic Water Discharge - Analyzed
An analysis of the Florida Department of Environmental Protection (FDEP) August 28, 2007 report to the city of Marco Island presents concerns in several areas. As this analysis was being prepared, the FDEP for all practical purposes ordered a halt to all dewatering. This report could explain the FDEP’s rationale for the halting, and details some of the adverse environmental impacts resulting from dumping effluence into the waterways.
To obtain the entire analysis, CLICK HERE.
To obtain the entire analysis, CLICK HERE.
posted by Mario R. Sanchez, Ph.D. at
10:40 AM
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Number of Comments: 3
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3 Comments:
The City of Marco Island continues to reach the goal of installing sanitary sewer lines to the remaining neighborhoods served by septic systems. Complex and conflicting environmental issues continue to challenge the method of construction. While reducing offense odors caused by the removal of ground water for sanitary sewer line construction, there may now be a concern for the microscopic marine life near the water discharge point.
The City, the Florida Department of Environmental Protection (FDEP), and the South Florida Water Management District (SFWMD) are working together to insure a continuation of sanitary sewer line construction that has the least impact to the local citizens and their environment. All agree that the long-term benefit to water quality and aquatic life will be improved when septic tanks are eliminated.
Yesterday afternoon, (8-30-07) City staff met with representatives from DN Higgins, Quality Enterprises, the SFWMD and the FDEP to discuss the dewatering activities on Marco Island and the results of limited water quality testing by the FDEP.
Following receipt of complaints from a citizen, known to oppose the City’s Septic Tank Replacement Program, the FDEP conducted limited testing to determine any negative impacts to the water quality in canals due to dewatering activities associated with the City’s sanitary sewer line project.
The water quality tests taken by DEP confirm a naturally occurring sulfate concentration in the surface water. The results of the sulfide readings show that invertebrate larvae may be impacted at microscopic levels through the City’s dewatering process.
In order to lay sanitary sewer pipe in a narrow trench, natural ground water is removed from the high water table through a “dewatering” process. Ground water is then discharged into swales or a storm water outfall, and then into canals.
Ground water on Marco Island contains high levels of sulfates and sulfides due to the decomposition of organic material (buried mangroves). When dewatering occurs, the sulfides/sulfates are released into the atmosphere and cause an offensive odor. To reduce or eliminate the odors caused by dewatering, the City asked its contractors to discharge ground water directly into the manhole above the storm water outfall pipes to the canals.
While direct discharge of ground water into the storm water structure reduced or eliminated offensive odors, there may be a negative impact upon microscopic marine life.
The potential hazard to microscopic marine life from sulfide is localized and transient. Sulfide is oxidized rapidly in surface water. Increasing oxygenation of the water would minimize any toxic effects on aquatic life of microorganisms.
It is unlikely that increased oxygenation will occur during the hot, summer months. Therefore, the City will again modify the dewatering process as it seeks new ways to eliminate offensive odors while maintaining water quality standards.
DEP results show a significant decrease in sulfide measured from the groundwater discharge location and contact with the surface water. This demonstrates the capacity to reduce concentrations in the water by returning to the original dewatering practices of discharging ground water into the swales. This allows the release of sulfides before the water flows into storm drainage outfalls to the canals.
The City of Marco Island continues to investigate how to allow its contractors to continue to remove ground water, since this is the safest and least costly way to install sanitary sewer lines. The City wants to balance the risk to microscopic marine life and its citizens so as to insure timely completion of the sanitary sewer project. While the concentration of sulfides varies significantly from one area of the City to another, construction activities will be altered to find the best balance throughout the City.
A few of the many options to resolve concerns are as follows:
1) Returning to the original dewatering method of discharge into the swales.
2) Reducing the pumping rate into the swales by 50% during the daytime hours.
3) Continuing to monitor and place the limits of construction barriers appropriately per the SFWMD guidance.
4) Vacuuming built up silt the outfall structures prior to use in dewatering.
5) Reallocating staff resources to monitor the dewatering activities more closely.
SFWMD is the lead agency regarding the dewatering activities, since they have issued the permits to the City’s contractors. DEP intends to provide their surface water sampling results to the SFWMD for their review.
The FDEP stated: "The centralized sewer project on Marco Island will provide water quality benefits to the estuarine and marine waters surrounding the Island by eliminating high density on-site sewage treatment systems (septic tanks and drain fields), which are known to contribute pollutants to adjacent surface waters." Additionally, the Water Management District echoed the importance of moving forward with the septic tank replacement program.
It is important to note that that while the focus of the meeting was specific to water quality, the health concerns that have been raised are still being addressed by the City.
An outside environmental consultant, ENVIRON(*), has been retained by the City and has prepared a sampling plan designed to assess the level of hydrogen sulfide emitted to the atmosphere during dewatering activities. Both ambient air monitoring and ground water sampling will be conducted. They will measure hydrogen sulfide levels in ambient air at various times and various locations throughout the island.
This work will be conducted by two public health scientists, Dr. Timothy C. Varney, Ph.D, P.G., C.I.H. and Dr. James L. Poole, Ph.D, C.I.H. in conjunction with Dr. Tom Gauthier, Ph.D., an analytical chemist/risk assessment specialist.
The City of Marco Island is committed to working with the SFWMD, DEP, Collier County Health Department and citizens to address the concerns about dewatering.
* ENVIRON is an international environmental, engineering and health sciences consulting firm with offices across the U.S. and Europe. ENVIRON has over 1100 employees and the services to the City of Marco Island will be provided by their Tampa, Florida Office.
Lisa M. Douglass
Public Information Coordinator
City of Marco Island
50 Bald Eagle Drive
Marco Island, Florida 34145
By
Mario R. Sanchez, Ph.D., at Friday, August 31, 2007 2:28:00 PM
Isn't interesting that with all that trenching and dewatering in our front yards only 20ft from our drain fields and there is no sign of any contamination from them. We have dug up miles of front yards and have not found one septic failure. The distance to the canals in the back is 4 times futher than the trenching. It looks like the only thing failing us around here is our city councel and city manager.
By
Anonymous, at Friday, August 31, 2007 4:58:00 PM
Lisa Douglas should move to Washington because she is a world class "spin doctor". Returning to pumping into the swales is an idiotic idea. I suggest that all water produced from the de-watering be trucked to the swales of our city councilors, manager and the spin doctor. The city of Marco has absolutely no regard for its citizens health, wellbeing or, lifestyle. I have to question WHY the city proceeds regardless of the consequences to the citizens health. The island is a disaster zone. If I were a tourist (season approaches) I would stay very far away from Mossville. They could care less if they gas you to death.
By
Anonymous, at Friday, August 31, 2007 6:17:00 PM
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