HDPE used to update Florida Keys sewage system
After you cross the 18-mile “Stretch” into the Florida Keys from the mainland, the world seems to turn at a happily slower pace.
By car, there is only one way to get there—a 127.5-mile, mostly two-lane road known as the Overseas Highway (U.S. 1). It travels along a patchwork of land and sea featuring 42 bridges, including the Seven Mile Bridge atop portions of the former Overseas Railroad.
Only an estimated 76,300 people are permanent residents of this swirl of seemingly endless islets that divide the Atlantic from the Gulf of Mexico, but each year some 3 million visitors flock to this multi-blue seascape to soak in all it has to offer.
They fish in clear, shallow waters for bonefish and tarpon, head for the deep sea to catch blue marlin and barracuda or angle from one of the many historic bridges.
They dive and snorkel in the Florida Reef—the only coral reef in the continental United States and the third-largest coral reef in the world. They explore shipwrecks, sail on beautiful boats and watch magnificent sunsets.
Others revel in the flora and fauna associated distinctly with the Florida Keys. They are home to the second largest marine sanctuary in the United States, which protects more than 6,000 species of plants, fishes, invertebrates and corals.
It’s a place where shoreline development is restricted in favor of sea grass beds and mangrove trees, which thrive in the salty sea and support a host of aquatic and bird life with a prolific root system that extends above the water.
There is a very real challenge in preserving and maintaining this dreamy paradise. The Keys’ sewage systems are outdated and do not adequately protect these pristine waters. The state is mandating that new central sewer systems be constructed and completed throughout the Keys by December 31, 2015.
The Florida Keys Aqueduct Authority (FKAA), which provides water services to more than 44,000 customers in the Florida Keys, is currently mitigating the problem along with Monroe County, other municipalities and the State of Florida. This joint program effort has a composite cost of about $800 million. One of the remaining projects is the Cudjoe Regional system in the lower keys, which the FKAA is currently building at a cost of $180 million dollars.
“Reducing nutrient loading to near-shore waters expeditiously is important to not only the environment and protection of the reef, but also the Florida Keys’ tourist-based economy,” said Tom Walker, manager of engineering for the FKAA.
According to the FKAA, the Florida Keys’ sewer systems have primarily consisted of cesspits, septic systems, aerobic treatment units and small, privately owned wastewater treatment plants that have provided little or no removal of nutrients. Disposal methods are also inadequate, with nutrients escaping from drain fields and injection wells because of the porous nature of the limestone substrate.
The decline in water quality and deterioration of the reef has been directly linked to the nutrients in human waste, studies show. Over time, this has created a biomass of macroalgae that is overgrowing sea grass and adult corals and obstructing the development of juvenile coral. It is also depleting oxygen levels, which chokes off aquatic life and degrades water quality.
The impact on the environment also comes at a financial cost.
The Florida Keys National Marine Sanctuary conducted a study in 2008 that concluded that a decline to the reef would be detrimental to the water activities that drive the Keys’ tourist economy. The Florida Reef supports more than 33,000 jobs and creates an estimated $2.3 billion in annual revenue.
To remedy this problem, most of the outdated systems are being replaced with a central wastewater system featuring an Advanced Water Reclamation Facility (AWRF) on Cudjoe Key that will treat nearly 1 mgd in accordance with state standards. Wastewater will be pumped to the AWRF from an expansive collection and transmission pipeline system.
Because of the Keys’ unique landscape, there are a number of challenges to overcome. The Keys are actually the exposed portions of an ancient and fossilized coral reef, only three feet above sea level, and since the pipeline system will connect seven islands—Lower Sugarloaf, Upper Sugarloaf, Cudjoe, Summerland, Ramrod, Little Torch and Big Pine—workers will be laying pipe under land and sea.
“Cutting through rock and [the] dewatering of porous lime rock coupled with maintaining traffic on U.S. 1, the only road in and out of the Keys, are some of the impediments being conquered,” Walker said.
The collection portion of the pipeline system is comprised of nearly 130 miles of PVC and smaller-diameter high-density polyethylene pipe (HDPE) that will use both low-pressure and gravity technologies. It will connect to a larger-diameter, 17-mile wastewater transmission system. The transmission pipe is being buried along U.S. 1 and ten bridge crossings using horizontal directional drilling (HDD) and bridge attachment methodologies. This includes the Niles Channel HDD crossing with 5,000 ft of 18-in. DR7 HDPE to a depth of 60 ft below the seabed.
After the nutrients are removed from the wastewater as treated at the AWRF, it will be injected into wells that meet Florida Department of Environmental Protection requirements.
The Cudjoe (Key) Regional Wastewater Service area is a 56-sq-mile area that will serve approximately 8,200 developed parcels and approximately 9,000 dwelling units.
The FKAA awarded three construction contracts to perform this mammoth undertaking. Layne Heavy Civil was awarded the design-build contract for the largest segment of the Cudjoe Regional Wastewater Service Area, which includes the Outer Islands Collections and Transmission System for about 5,000 customers on Lower Sugarloaf Key, Ramrod Key, Little Torch Key and Big Pine Key.
“Layne is pleased to partner with the Florida Keys Aqueduct Authority and Monroe County to implement this crucial design-build project, which will protect water quality in this beautiful marine environment,” said Wesley Self, P.E., DBIA, program manager.
The project is currently within budget and has received $30 million in grant funding from the State of Florida to help finance the project.
HD Supply Fusible Piping supplied nearly 1 million ft of HDPE and fusible PVC pipe for Layne’s portion of the project, as well as the sale and rental of McElroy pipe fusion machines. HD Supply Fusible Piping has been involved in the material design and pipe selection, so the products were perfectly suited for the application.
The smaller-diameter 1-¼- to 8-in. HDPE pipe is being connected to residential properties via grinder pumps extending from the main lines. Layne has been using McElroy’s hand-operated Pit Bull fusion machines to butt-fuse tees and fittings.
“HD Supply Fusible Piping is always working hard to bring dedicated service and value to all our customers and the owners of these projects,” said Paul Dreher, fusible product manager, HD Supply Fusible Piping. “With technical expertise as the job is being engineered and onsite contractor support once the job is being built, we are proud to have played a major role in the success of this world-class project.”
The transmission system will include a pumped transmission main with six island-specific booster pump stations. The pipe selected was 18-in. HDPE pipe, which was being butt-fused and staged on a narrow land strip south of the Niles Channel along U.S. 1 in February.
Since then, Layne’s design-build team—including Utility Services Authority LLC as a subcontractor—provided design and permitting services for a 5,217-linear-ft, 18-in. HDPE directional bore beneath Niles Channel connecting Ramrod Key to Summerland Key. They performed this record bore in one 18-hour shift ahead of schedule.
To avoid clearing mangroves and disrupting wetlands habitats, Julie Cheon, water quality and environmental manager for the FKAA, said the company will use slip-lining and cured-in-place pipe (CIPP) techniques where possible.
Red, black and white mangroves are a main feature of the Florida Keys Overseas Heritage Trail, which is popular with runners and cyclists, runs parallel to U.S. 1 and will eventually connect the entire 106 miles of the Keys, from Key Largo to Key West.
These forests are credited with reducing erosion, protecting the shoreline against tropical storms and providing shelter and food sources for fish and other aquatic life.
Monroe County is requiring all developed properties to connect to the new centralized wastewater system where it is available. Those in more remote areas, where connection to the central system isn’t feasible, can opt to participate in an on-site wastewater nutrient removal system program operated by the FKAA.
These significant upgrades to wastewater treatment and disposal will play a huge role in protecting the Florida Keys unique ecosystem for generations to come.