Dump the Pumps, Inc.
P.O. Box 1956
Big Pine Key, FL 33043
January 29, 2015
Jonathon E. Shaw, P.G.
South Florida Water Management District (SFWMD)
PO Box 24680
West Palm Beach, FL 33406
Subject: Application No.: 150121-6 (Lower Sugarloaf Key Master Lift Station)
Dear Mr. Shaw:
Dump the Pumps, Inc. (DTPI) was made aware of the “Minor Modification- Cudjoe Regional Wastewater Collection System D B Project (Application #150121-6), County: Monroe S3/T67/R27” via our corporate attorney Lee Rohe, Esq. , who received notice from SFWMD per standing request for notification of permit activity. While DTPI does not intend to file a formal Petition against this permit modification because it is out of the scope of our donated funding purpose, our technical advisory team feels that SFWMD should be aware of several serious environmental concerns that were identified in a brief review of the application.
As you may be aware, DTPI has challenged numerous permits in the Cudjoe Regional Wastewater System (CRWS) due to environmental concerns arising from the seriously flawed engineering design. Most of these design inadequacies appear to have arisen from the decision to design a sewer collection system based entirely on collection system pumping by the E-One brand one horsepower positive displacement grinder pump. These residential grinder pumps are even being utilized inappropriately and in violation of national life safety codes in neighborhood lift stations.
In order to make these little E-One pumps appear adequate, assumed parameters of the design were modified, perhaps recklessly. For example, in the collection area served by the subject permit modification (Lower Sugarloaf), the assumed average daily wastewater production per EDU (equivalent dwelling unit) was reduced from 235 gpd/EDU, as determined by Brown & Caldwell based on water use data supplied by FKAA, to only 135 gpd/EDU. Engineering firm CH2M Hill adopted the Brown & Caldwell gpd/EDU conclusions as realistic during its subsequent analysis and technical report. If Brown & Caldwell’s assumption is closer to the truth than Chen-Moore’s (which assumes a ridiculous percentage of water being used for irrigation), then the entire system is undersized and may not be capable of pumping all of the wastewater entering the system. The excess can only overflow into the (protected) environment. Furthermore, Brown & Caldwell determined from a study of existing nearby treatment plants that a peaking factor of 4.5 was more appropriate to the highly variable population of this area with its very high seasonal occupancy and periodic tourist influx. The calculations used to determine required capacity of the pumps in the subject pump station were based on a peaking factor of only 3.7, per a standard formula based only on population as found in the “10 States Standards”. The factor determined by actual engineering study was ignored. Consequently, even if the Chen-Moore assumption of average gpm/EDU were adequate, the inappropriate peaking factor might still result in overflows.
DTPI’s technical review team alerted to several concerns on Exhibit 3 of the Application. Said Exhibit 3 is an engineering drawing of the master pump station for which a dewatering modification was requested. It was noted that the surrounding ground elevation is +1.30 feet geodetic above sea level, although a note states that ground water was encountered at elevation +0.5. The blue line on Exhibit 3 is actually shown at elevation zero, so the diagram is somewhat misleading. Doing the math, we find that the water table is only 9.6 inches below the surface. From Exhibit 1B it is apparent that this master pump station is on an open waterfront lot and the pump station is in very close proximity to the bay shoreline. This pump station has a 10 foot diameter wetwell, capable of storing 587 gallons per foot of depth. There is 4.8 feet of freeboard above the high level alarm, which translates to a reserve capacity of 2,818 gallons. At the lower officially assumed peak flow into the pump station of 192.5 gpm, a failure of the pumps to operate would give the wastewater department of FKAA less than 15 minutes from receipt of the high level alarm to respond to the scene and resolve the issue before the pump station overflows into the adjacent bay. Such a response and repair time is obviously unlikely. Pumps might fail to run due to a generator “fail to start”, due to a control system failure, lightning strike, and other. The pumping may cease due to blockage in the forcemain. A blockage is not unlikely considering that peak flow velocity is shown at 2.05 ft/sec. A velocity of 2.0 ft/sec is considered the bare minimum to discourage deposits of grease and accumulation of solids. A velocity of 3.5 to 5.0 ft/sec long enough to exchange the contents of the pipe at least once a day is considered essential to re-suspend wastewater constituents if the flow in a forcemain is intermittent. Intermittent describes the operation of this pump station perfectly , and therefore the forcemain may be expected to clog. There is no quick solution to a clogged forcemain. Raw sewage will overflow. Closing a valve on the collection forcemain to stop the flow into the pump station is not an option because the E-One pumps upstream are positive displacement with no pressure relief. They are stated to reach 180psi and may go higher, not counting the surge from shutting a valve. These pumps generate pressures exceeding the ratings of fittings and the test pressure of the piping they feed. A closed valve will simply result in a break and raw sewage spill elsewhere.
Somebody besides DTPI should be concerned about the environmental risks posed by the CRWS design, but so far FDEP South District has ignored the many issues and the many violations of required minimum design standards. Perhaps SFWMD is also unconcerned about design inadequacies, but SFWMD must surely be concerned about what it is permitting with this modification.
It is stated that the nearby monitoring well indicates contamination of the soil by the presence of the octane boosting gasoline additive MTBE. MTBE is “highly soluble” in water. The site of dewatering is clearly shown near the Gulf shoreline and a deep boat basin. The approved plan is to excavate a 15 foot by 12 foot hole to a depth of 15 feet, located between the pump station and the monitoring well in the contaminated ground water. and to fill this hole with #57 stone. The #57 stone is the common coarse pea-rock often used as a non-muddy surfacing on unpaved parking lots and also often in lieu of sod in the Keys.
What FKAA’s contractor is proposing is to build a permanent “French drain” immediately adjacent to (or within) known MTBE contaminated soil. This French drain would extend to a depth approximately 13 feet below the tide level, very near shore and the boat basin. The French drain may also penetrate a confining cap-rock layer, and it may also transect a hydraulic conduit to the ocean that would allow very rapid transport of MTBE to the protected nearshore waters.
Since the water table is only about 9” below ground and the French drain is full of rock (and existing tidal groundwater), there is no way to get enough hydraulic head to effectively dewater the pump station without building a berm around the excavation so that the pumped excavation water is significantly above grade. That was not mentioned in the Application. The pump station excavation itself is shown as being 20’x20’ and the depth to allow placement of a gravel base for the wetwell would be approximately 15’. Depending on the backfill material, this wetell excavation may also serve as a French drain for MTBE contaminated ground water.
The stated methodology of the dewatering can only be considered sheer fantasy: “Dewatering will be limited to less than eight hours total, dispersed over several days, and the drawdown of the water table will be minimal (less than two feet)”.
If the dewatering is of less than two feet of water depth for a 15 foot installation, then dewatering is not required at all. A two foot drop of the existing water table would not even dewater to the depth of the valve vault adjacent to the wetwell. It would also not dewater to the invert of the influent pipe that is required by FKAA Specifications to be laid in a dry trench.
If this seriously flawed design is to be built in spite of all our warnings, DTPI suggests that the pump station wetwell that is the subject of this permit modification be excavated and set under water with no attempt to dewater. The adjacent valve vault can be modestly dewatered into the influent pipe trench. The backfill for the pump station wetwell should not be loose gravel, but rather fine limerock to discourage the French drain effect. Under no circumstances should a 15’ deep French drain be installed in contaminated soils. Please consider voiding this permit modification now that you have a better picture of the situation. Thank you.
Dump the Pumps, Inc.
Banks Prevatt, President
CC: (via email)
Jerry Buckley, Dept. of Environment and Economic Opportunity
Dept. of Environmental Protection- West Palm Beach
Brian Powell, USFW
Natural Resources Defense Council
Nancy Finley, National Key Deer Refuge