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Proven geosolutions for Florida landfill expansion

August 1st, 2010 / By: / Feature, Geosynthetic Clay Liners

Introduction

The combined efforts of industry experts make it possible to complete large, complex projects on time, on budget, and with the highest regard to quality.

In 2009, the 62-acre expansion of the Sarasota Municipal Landfill was the state of Florida’s largest single landfill installation. In addition to adhering to state and federal regulations, Sarasota County requested that the design accommodate future vertical expansion, which could double the height of the landfill. Provisions for potential leachate recirculation, bioreactor operations, and methane reuse were also built into this design.

The design specified a double synthetic liner system. From the prepared subgrade up, this landfill system consists of:

  • a geosynthetic clay liner (GCL) alternative clay foundation.
  • a secondary layer of textured 60-mil HDPE liner.
  • a geocomposite leak-detection layer.
  • a primary layer of 60-mil textured HDPE.
  • a primary layer of 60-mil textured HDPE.
  • 2ft (0.6m) of sand that functions as a protective cover layer.

The site itself is just 20ft above sea level and is surrounded by protected wetlands (see aerial photo in the box above). In addition to the delicate nature of the environment, the installation had to be completed between Florida’s rainy season and its hurricane season, a time frame of less than six months.

Experts hired

Understanding the value in hiring experts to accomplish specialty work is a key for success in this type of venture.

Coordinating all of the subgrade preparation with the manufacturer, along with aligning transportation and the liner installation materials, required the expertise of three companies that had an extensive history of working together. “Before the county awarded the project, they had us call around and do a detailed check of all the contractor and subcontractor references,” explained Tom Yanoschak, an engineer with HDR.

“They wanted to be certain that the companies that won the bid had a good performance record and a good reputation for working together. A project like this is too big for one company to handle and too important to be compromised if communication breaks down.”

Go time

In any landfill installation, timing is crucial. Well before the official notice to proceed, GSE, G-SI, and Glover coordinated the equipment, personnel, and materials necessary to execute such a large project within the designated time frame.

“Glover and G-SI work very well together because they have a clear division of responsibility,” said Steve Eckhart, vice president of sales and marketing at GSE. “They have very good communication so everyone knows who is responsible for what along the way, which is why they have never had a job run over.”

Three weeks prior to beginning construction, Jerry Walski, site superintendent for Glover, relocated to Sarasota to prepare for the project. This included mobilizing the 150-person workforce and selecting the fleet of heavy equipment from the company’s inventory.

Twenty-two years of experience made Walski well-qualified to do the initial construction assessments and staging. In the case of the Sarasota expansion, the existing landfill was fully operational, so preparation also meant gaining familiarity with the people who worked there. Walski also held several meetings with county officials and members of the HDR engineering firm to ensure a smooth start to the project.

In advance of G-SI’s mobilization, Glover prepared landfill cells #1 and #2 for liner installation. The first task was to ensure that the site was secure.

“You make sure that erosion controls are in place or you don’t start work,” said Walski. As the job progressed, the compaction, slopes, and grades of the site were perfected. To complete the groundwork, Glover installed the leachate collection system, placed the pump station and manholes, laid approximately 2 miles of leachate force main, and stockpiled liner material for G-SI.

While Glover executed the preliminary site preparations, G-SI organized everything related to liner installation. Ongoing contact with manufacturer GSE ensured that liner materials were produced and delivered to the site on time for construction.

“We use GSE as our supplier for liner materials because they have the capacity to make every kind of geosynthetic and geotextile used on virtually any project,” said G-SI project manager James Larsen. “Having one source for everything is a big advantage. It significantly streamlines the logistics of moving materials.”

Larsen also made arrangements to have specially outfitted skidsteers, used to dispatch the rolls of geosynthetics, onsite. A hand-selected crew of experienced laborers and well-trained technicians from G-SI’s workforce also relocated to Sarasota where they remained for the duration of the installation.

If it was easy, everyone would do it

GSE’s tight control in manufacturing the geosynthetics, from raw materials to delivery, was only half of what determines whether a liner system will perform. The rest is determined by how the materials are cared for on the job and how they are installed.

“We don’t sell our materials to everybody who asks us for a bid,” said Eckhart. “There is a lot of liability attached to these things and a lot at stake. We only partner with people if we have confidence in their work. They must fully understand the materials and have the same commitment to quality as we do,” he said. “Basically, after we sell a job we don’t want to get any phone calls.”

Due to the sheer size of the Sarasota Landfill expansion, the project was completed in four 13-acre cells. This required careful coordination between Glover and G-SI.

Glover started construction with the preparation of the subgrade. Federal regulations require a 2-ft layer of clay for the first layer above the subgrade in all liner systems. Since there was no appropriate clay in the vicinity, the first layer G-SI installed was a geosynthetic clay liner (GCL), a geotextile infused with bentonite clay. This GCL has the same performance value of 24in. of clay, but it is extremely sensitive to moisture, requiring immediate cover.

G-SI installed all the layers of the liner system in one section before moving on to the next. Once a section was completed, Glover topped it with 2ft of protective sand. “We work hard to get out of their way, and then they work hard to get out of ours,” said Walski, Glover’s site superintendent.

Testing

Larry Boles, G-SI’s site superintendent for the Sarasota project, had 23 years of experience installing liners. In Sarasota, Boles started every working day with a safety meeting that outlined the day’s objectives.

In addition to the third-party quality control, every member of the G-SI team attended these meetings. “Production-wise, things go a lot more smoothly when everyone on the team is in the loop,” explained Boles, who worked closely with Glover’s Walski.

As the installer, G-SI was responsible for quality control regarding the liner. Its team conducted and recorded the standard quality assurance tests during the installation. Samples of the liner seam were taken every 500ft and pulled apart by a tensometer, which measures seam stretch under strain.

Destructive tests were also performed on each panel, which required extracting a circle of liner and performance testing it. The location and results were recorded, and then the hole was patched using an extrusion welder. The information collected from these tests was compiled into a report for the state to review prior to issuing the permit for use.

Quality

Standard tests measured the performance of the liner material, but quality liner installation includes how the contractor, installer, and supplier work together.

The huge Sarasota Landfill expansion, with its limited time frame and special environmental considerations, demanded expertise that can only come from a team of seasoned experts. “We have done similar projects with Glover and G-SI many times before,” said Eckhart. “We all share a commitment to quality. Installations have a lot of moving parts, and to make everything go smoothly each company has to have confidence in the abilities of the others.”

Source: Geo-Synthetics Inc.
Ron Bygness, editor of Geosynthetics magazine, also contributed to this article.

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