Miami-Dade Water and Sewer Department (MDWSD) recently completed one of the largest lateral lining projects in the country, rehabbing approximately 1,200 laterals in residential and commercial areas at a price tag of just under $5 million.
The 15-month lateral project was part of a pilot program that MDWSD undertook to research and evaluate a variety of lining techniques in addressing the condition of its laterals and stopping infiltration-and-inflow (I/I). In the past, I/I was handled through traditional dig-and-replace methods.
The pilot project, called the Miami-Dade Pilot Lateral Lining Project, was a two-part program that first inspected and identified the problematic laterals and then had them lined using trenchless technologies.
“The main purpose was to determine whether lateral relining was a solution to our peak-flow problems in the system,” explains Rod Lovett, chief of the MDWSD sewerage collection division. “Most of our laterals are conventional replacements where we go and dig them up and replace them. Being in Miami-Dade County, that typically is the cheapest way to go. However, we have some exceptions to that rule and we really wanted to test the lateral linings to see if they are a solution to the leaks in the system.”
The project engineer was Hazen and Sawyer. MDWSD put the project out to bid and awarded it to Metro Services Inc., which utilized Perma-Liner’s InnerSeal and standard Perma-Liner systems on approximately 1,200 laterals in the system between June 2006 and November 2007. As the general contractor, Metro Services handled the majority of the laterals but some work was subbed out.
“By the sheer number of laterals relined, this was probably one of the largest such projects in the country,” says Jorge Godoy, president of Metro Services Inc. “[MDWSD] identified the laterals that were leaking. Our primary job was to eliminate inflow.”
The area of the project involved about 80 percent residential and 20 percent business. Miami-Dade’s pipes are mostly made of clay but there is a fair amount of cast-iron, which were turburculated and required cleaning before lining. The Miami-Dade system also has more than 1,400 pump stations, with pipes 6 to 8 in. in diameter. The laterals range from 8 ft in length to as long as 100 ft. The laterals range in age from 20 to 50 years old and suffer from heavy infiltration, cracks and root intrusion.
“The condition of Miami-Dade’s laterals is typical of the rest of the country, except for the fact that Miami-Dade has a very high water table and all the pipes are under water,” explains Steve Cudd, CIPP project manager for Metro Services Inc. “Like a lot of cities, Miami-Dade addressed its pump stations and mainlines. After those, they realized that the next part of the process were the laterals. Because although they eliminated a lot of the inflow into the mainlines, they had not addressed the laterals and there was a great deal of water coming in there as well.”
To assess the condition of the pipes and laterals to identify the source of rain-induced I/I that comes into the system during and after heavy rains, MDWSD used a sanitary sewer evaluation survey (SSES), which uses various equipment and techniques to detect sewer pipe defects, blockages and capacity problems. These techniques include smoke tests, dye tests, closed-circuit TV, flow monitoring, rain monitoring, building service connection location/inspection and flow isolation.
Once MDWSD identified the problematic laterals, issuances were given to Metro Services to begin work. First, Metro crews used a CUES lateral investigative unit to look at the selected laterals to determine which ones needed to be cleaned and prepped before liner installation could take place. Crews utilized a Perma-Liner InnerSeal unit with a 28-ft trailer, which is used as a turnkey operation, to do the lining. A smaller trailer was used when the standard Perma-Liner process was used.
How InnerSeal Works
Perma-Liner’s InnerSeal, which Metro Services used on a majority of the laterals, is a non-intrusive lining method to correct lateral pipeline and mainline sewer pipeline connection problems. The materials are designed to be placed from within the main sewer pipe and launched into the lateral, creating a watertight seal at the main and lateral connection point. The lateral is also lined at the same time, correcting any damaged pipe sections and preventing roots from growing into the pipeline. The InnerSeal resin technology has excellent bonding properties in all pipe materials and does not contain styrene. Resin formulation is an ambient cure and can be modified for hot water or steam curing.
“The process itself takes about two hours and we could easily do four laterals at a time,” Cudd says. “We would do the first one and while it was curing, we would leave air on it and go start another and then repeat the process.”
Metro typically used six-person crews for this project. Cudd says Metro’s goal was to line five to seven laterals a day. “And we usually completed seven [laterals]a day,” he notes.
Though huge in size, the project itself didn’t present any special challenges for Metro, Cudd says, explaining the project simply: “We just had to go through the cleanout, check the length of the lateral, status of the pipe and then clean it and reline it.” Lateral ownership wasn’t an issue as the laterals were addressed from the property line back to the mainline. If a cleanout needed to be installed, it was done on the county side of the property line, Cudd says.
Both Metro and MDWSD were more than satisfied with the project’s outcome. MDWSD is still waiting for enough qualified rain event data to fully analyze the results of the pilot program.
“We were initially pleased with the results of the lateral work and so far they have held up and have given us good service,” Lovett says. “They’ve eliminated 100 percent of the leaks we had in those laterals.”
Beyond the project’s final results, Lovett was also pleased with the use of the Perma-Liner process, which he says gives a 50-year life expectancy. “The InnerSeals were very good,” he says. “There was some discussion before we started that the InnerSeals wouldn’t adhere against the normal pipe material or mainline lining material. We found that to be untrue and they seal well against both materials. They stopped the leaks.”
Sharon M. Bueno is managing editor of Trenchless Technology.