Sewer pipes to go under bridges along highwayBy Steve Estes
The new wastewater collection system for the Cudjoe Regional area will span several bridges along US 1 before its completion in what is expected to be just over two years.
But where the pipes run across those water channels may change as the project progresses.
Last week, the Florida Keys Aqueduct Authority Board approved changing the sewer pipe that will traverse Bow Channel and Kemp Channel in the inner islands collection system portion of the project from an above ground configuration to one below ground.
The original design for the inner island system called for the transmission pipes to run alongside the bridge decks, hanging over open water.
But the contractor suggested that, with the enhancement of directional bore technology, the pipes could go under the bridge, across the channel for little increase in overall price.
The above-ground piping was to be weather sealed against corrosion by wrapping wax tape around the exterior of the iron pipe. That cost was bid at just over $130,000.
By using directional boring, drilling through the sea bed inside the rights-of-way for the bridges and pulling the pipe through to re-emerge on the other end, the cost rises to just over $178,000.
FKAA staff recommended that the directional bore be used for various reasons.
“The future plans of the Florida Department of Transportation call for replacement of the bridges in the project area within the design life of the proposed force mains,” states the staff report to the FKAA board. “FKAA wishes to take advantage of the present worth value of installing these mains by alternative means now (horizontal directional drilling under the waterways) rather than have to replace them in the future.”
FDOT does not have any major bridge replacements built into its current five-year work plan for US 1 in Monroe County, but many of the bridges are approaching their anticipated structural life span and the state agency is expected to begin a phased replacement of the US 1 bridges over the next 10 to 20 years. The anticipated life span of the Cudjoe Regional system is 30 to 40 years.
Because the change to directional boring instead of bridge-mounted pipes will increase the contract price of the inner islands system, FKAA may require final approval of the Monroe Board of County Commissioners.
“There is some contingency money built into the financing package for the Cudjoe Regional and as long as changes can be made inside that original financing plan, minor change orders are acceptable,” said County Administrator Roman Gastesi.
But he expects that FKAA will bring changes of this nature to the BOCC.
“The life cycle cost analysis for directional boring versus above ground pipes has to be weighted heavily in favor of boring I would have to believe,” said Gastesi.
“A move like this makes sense from an engineering standpoint,” said County Engineer Kevin Wilson. “No matter what happens with the bridge later, the sewer pipes will be able to remain in place and we won’t have the expense of replacing the pipes with the bridge.”
FKAA and county officials have already determined that Niles Channel between Summerland and Ramrod Keys will be traversed using directional boring and there is $3.4 million built into the system financing plan to cover that cost already, says Gastesi.
Design plans are not yet complete for all of the outer island portions of the Cudjoe Regional,which includes Lower Sugarloaf Key and Ramrod through Big Pine. Work has already begun on Lower Sugarloaf and Ramrod.
The outer island system will also have to cross several US 1 bridges with transmission lines and both Gastesi and Wilson believe that directional boring may well be the ultimate answer for those bridges as well.
“The technology for directional boring has advanced tremendously in the last few years, making it a better long-term investment than it was a decade ago. It would make sense to do as many bridges as possible with directional boring if the cost differential is manageable,” said Gastesi.
The outer island system will have to cross Torch/Ramrod Channel and both Pine Channel bridges before completion.
The BOCC has not yet signed off on changing the proposed design from above ground to directional boring, maybe because it hasn’t been brought to the BOCC yet, says County Mayor George Neugent.
“We seem to be having a communications issue with FKAA right now and we don’t learn everything we need to know far enough in advance to make meaningful decisions,” said Neugent. “That’s a problem that we have to fix.”
Several subdivisions in the inner island system have balked at the higher use of low pressure grinder pump systems than had been originally anticipated, but the BOCC hasn’t taken any affirmative action on those concerns, voting to maintain the status quo and allow the project to proceed as designed.
“We need to be aware of what is happening with these systems. We’re paying for them and if there’s some issue we don’t like or would like to talk about, we need FKAA to be forthcoming,” said County Commissioner Heather Carruthers.
“If they need more money for some part of the project, they’ll have to come to us anyway,” said Commissioner Danny Kolhage. “Better for them sooner than later.”
During the most recent update of the Cudjoe Regional progress, FKAA engineers announced that eight miles of pipe had been put in the ground on Cudjoe Key, and that site prep and installation of pipes had begun on Lower Sugarloaf and Ramrod. The design for Little Torch and Big Pine Key is more than 90 percent complete, but work on those two islands probably won’t start until after mid-year next year.
The foundation for the treatment plant on Blimp Road was poured last week and that facility should start to rise very soon.
According to Wilson,the construction schedule has the completion of the treatment plant land the availability of connection pipes on Cudjoe Key happening just about the same time.
“It will be a very short time span from completion of the treatment plant to actual flow from the inner islands collection system,” Wilson said.