Author: Professor, Dr. Dietrich Stein - TrenchlessOnline

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COVER STORY Trenchless Thrives In the early 1990s, the Miami-Dade Water and Sewer Department (MDWSD) had in all likelihood the largest chemical grouting program for its sewer collection system in the United States. With its fleet of 16 television and grouting systems and trained crews, Miami-Dade was at the forefront of addressing its infiltration-and-inflow (I/I) problems with the latest technology. Fast-forward to 2007 and MDWSD is still on the cutting edge of departments involved in rehabilitating their infrastructure.Today, the use of curedin-place pipe (CIPP) and lateral inspection and relining replace chemical grouting at the top of the agenda of work being done in the county. “The collection system is in better shape today than it has been in 10 to 15 years,”says Rod Lovett, chief of the MDWSD sewage collection division. “We started with a consent agreement [with U.S. EPA] in 1992 and we’ve done in total since then about $400 million to $500 million worth of work on the system. We analyze the repair method that is the least expensive way to make the repair and a good portion of that has been through trenchless technologies.” MDWSD’s budget for trenchless has grown over the years as opportunities Trenchless Methods Remain Key to the County’s Water and Sewer Rehab Success By Sharon M. Bueno for use has expanded; approximately 40 percent of its rehab budget is spent on trenchless projects. Through the use of fold-and-form (early on), CIPP, sliplining, pipe bursting, horizontal directional drilling,TV inspection, sectional and point repairs and chemical grouting of joints, the water and sewer divisions in Miami-Dade continue to invest wisely in its infrastructure — something all utilities need to be doing these days, Lovett says. “The state of the infrastructure in Miami-Dade is the same as the rest of the country — it is in desperate need of replacement,”says Luis Aguiar,chief 20 TRENCHLESS TECHNOLOGY September 2007 www.trenchlessonline.com
in Miami-Dade, Fla. of the water transmission and distribution division.“We need to continue to invest money to replace the infrastructure because it is getting to be 50 to 60 years old or older. We have water mains [in Miami-Dade] that have been in service since the early 1930s. It is a challenge being faced by not only Miami-Dade but every utility across the United States where the infrastructure is getting to the point that unless we start investing money in it, it’s going to become catastrophic in the future. And it’s not just the water and sewer systems. Look at the steam pipe that blew in New York City and the bridge that collapsed in Minnesota [this summer].” Miami-Dade County is home to the fifth largest utility in United States, in terms of miles of service and customers. MDWSD, with 440 sq miles of service area, maintains 7,100 miles of water lines and 3,600 miles of sewer lines, which serve approximately 2.4 million customers and includes 11 wholesale municipalities. The average age of the sewer and water lines are 40 and 60-plus years old, respectively, with some sewer lines dating back as far as 1919.A majority of the sewer lines are made of clay with new pipes being fusible PVC; the forcemains are made of ductile iron and prestressed concrete. MDWSD operates three water and wastewater treatment plants each, along with 14 pump stations for water service and 954 pump stations for wastewater. Trenchless Baptism Trenchless methods made their first appearance in the county in the early 1990s when fold-and-form (F/F) was used to rehab aging sewer lines, as it was considered more cost-effective at the time than CIPP, says Lovett and Aguiar. “We did some successful fold-andform programs,” Lovett says.“But now we are pretty much exclusive to CIPP. www.trenchlessonline.com As we progressed, the patents on the CIPP process wore off and as competition came in, the price went down. We have a contract now that we pay $21.50 per foot for 8-in.CIPP,which is actually less money than what we were paying for fold-and-form.” So far this year, Miami-Dade has The Miami-Dade Water and Sewer Department completed more than 40,000 ft of CIPP work so far in 2007. done 40,600 ft of CIPP work.“That’s probably down from previous years,” Lovett notes. “We are going back through the system [with inspection] a second time; therefore we are not finding as much of a problem as we did the first time.” Back in the early days when everything trenchless was new, people were coming out of the proverbial woodwork, offering Miami-Dade can’t-miss solutions and products to its infrastructure problems. “About that time, everyone was coming down here with a magic wand, saying ‘I got the process that’s going to solve all your problems,’” remembers Aguiar, who at the time was working on the sewer side. “It was then we decided to hire a consultant and form a committee so we could evaluate the different processes and materials that [were being pitched] to us… That is how we started to expand our trenchless program.” The district’s trenchless program has included over the years a variety of methods and trenchless companies, including some large diameter and interceptor sliplining work in the mid-1980s using HOBAS pipe, a program that lasted until the late 1990s. Pipe bursting has been used on the sewer side involving TT Technologies but is being utilized to a far larger extent on the water side today.Televising and grouting the sewer lines, once the main cog in its trenchless arsenal, used such companies as CUES. Regrouting annular space for liners added Logiball to the mix. Today, CIPP continues to be the most used trenchless method, contracting the work out to such companies as Insituform Technologies. Laterals are taking center stage these days with companies such as LMK and Perma- Liner among others getting the call. “Miami-Dade County Water and Sewer has always been very conservative,”Aguiar says.“It took a lot of effort to accept technologies that were really new to the U.S. market. So we had to take certain chances.” The televising and grouting program was one such chance, using technology that wasn’t largely accepted by many utilities at the time. Through the program, high levels of I/I were vastly reduced over a fiveyear period between 1993-98. The program proved invaluable to MDWSD and not just in terms of the I/I results but in the knowledge gained by its staff. “We had to learn September 2007 TRENCHLESS TECHNOLOGY 21
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Author: Professor, Dr. Dietrich Stein - TrenchlessOnline

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