Alabama County Promotes All-Inclusive Approach to I&I Mitigation

Huge investments into sewer capacity left Southern community looking for answers when SSOs continued.

Alabama County Promotes All-Inclusive Approach to I&I Mitigation

Daniel White, left, deputy director of engineering and construction for the Environmental Services Department of Jefferson County, discusses a work project with Tad Powell, a consulting engineer with Hazen and Sawyer. 

Interested in Manholes?

Get Manholes articles, news and videos right in your inbox! Sign up now.

Manholes + Get Alerts

You often hear from municipal sewer officials how important it is to have a comprehensive plan to address I&I, but few utilities better exemplify the concept better than Jefferson County, Alabama.

When the county received a consent decree in 1996 to reduce its release of untreated water, it invested roughly $2.4 billion in collections system and treatment improvements. But it learned that this investment would not be enough to combat ongoing sanitary sewer overflows and capacity issues during peak flows.

Embarking on a comprehensive approach to mitigate inflow and infiltration by using modeling and viewing its system as a whole versus the traditional practice of single components has enabled the county to significantly reduce its I&I without the need to upsize assets — all while removing issues during peak flow events. 

The confrontation begins

From 1996 to 2006, Jefferson County embarked on an aggressive program to meet the mandates of a consent decree from the U.S. Environmental Protection Agency. During this period, roughly 20% of its collections system was renewed either through capacity improvements, replacements or trenchless rehabilitation. In total, approximately 3 million feet of pipe were addressed and a high degree of success was achieved, as the volume of its releases saw more than a 98% reduction. Unfortunately, even with its large investment, the county still struggled with SSOs in some of its smaller-diameter sewer mains and experienced capacity issues during peak flows.

Later, in 2011 as the consent decree work was winding down, Jefferson County decided to begin a program with the help of consulting engineers Hazen and Sawyer to meet the remaining requirements of the consent decree in all of the basins previously identified.

Because of all of the funds that had been spent to improve the system and the disruptions to the financial markets following 2008, the county found itself in bankruptcy in 2011 and with some of the highest sewer rates in the country. Local government and politicians were pushing back against rate increases to fund the additional work that would be needed — above and beyond what had already been spent — to bring the system into compliance. There was a small amount of cash on hand for capital improvements, but it needed to be spent wisely.

“We needed to make sure every dollar we spent was going to produce a good result. But how do we do that?” asks Daniel White, deputy director of engineering and construction for Jefferson County Environmental Services. “The system was too large for us to just approximate where we had the largest need and where the priorities should be placed. So we took our time and focused on planning efforts to develop a good asset management plan before we kicked off the next phase of projects and investments.”

Enlisting help

In 2011, Jefferson County had enlisted Hazen and Sawyer to assist with a project at its Village Creek treatment plant. The project was successful and fostered a great working relationship, so the county didn’t hesitate to reach out to Hazen and Sawyer for assistance with developing a strong collections system asset management and maintenance program to continue I&I mitigation efforts. Hazen and Sawyer also had extensive experience creating a similar program for another client that was experiencing many of the same issues, making it an excellent match.

The county and Hazen and Sawyer worked together, developing a plan that was driven by modeling and asset condition assessment to determine where the county should focus its priorities and limited funds. Luckily, through the consent decree work, the county had already established a robust and extensive flow monitoring network with approximately 150 flow monitors spread throughout the system’s nine sewer basins and 176 pump stations. This allowed them to see what was happening and where the largest peak flows were occurring.

Although CCTV inspection data had been collected under the consent decree program, it was captured in a format that did not allow the ability to store or record asset condition. The county needed to begin from scratch and inspect the lines to collect new data for incorporation into its CityWorks asset management software.

Taking it in small chunks

How do you eat an elephant? One small bite at a time. This is the approach Jefferson County decided upon. One basin area known as the Chapel project was determined to be an excellent starting point for this new approach.

The Chapel project included a pump station with a flow capacity of 84 gpm. Peak flows from a two-year average of 24-hour storms were measured at 390 gpm — impossible for the pump station to handle. The county was initially considering upsizing the pump station, which would also require upsizing all of the downstream sewer, but county officials and Hazen and Sawyer associates felt that didn’t make sense.

“And this is where a change of approach all started,” says Stephen King, associate vice president of Hazen and Sawyer and program manager for the Jefferson County Asset Management Program. “Our approach for rehabilitation and drying up the I&I shifted to attack service connections — something that had never been done before in Jefferson County because the county doesn’t own the service connections. However, we made the decision to address the laterals anyway because it appeared to be in the best interest for the county to try and see if this solution would work.”

This would be the first project where the use of rehabilitation technology would allow the county to forgo other capacity improvements. It had performed much CIPP in mainlines in the past, and that had proven itself a solution for reducing I&I, but lining the mains alone wasn’t the silver bullet the county needed to resolve the ongoing issues.

Lateral CIPP lining was determined as the best option for the county since the materials have a long life span and the ability to truly eliminate I&I and seal the system. “We researched and considered products that could be tested and would be installed by prequalified contractors who had extensive experience with the installation. We wanted to build a long relationship with an installer and the products they would provide and recommend,” says Tad Powell, senior associate of Hazen and Sawyer and construction manager for the Jefferson County Asset Management Program.

They selected BLD Services of Kenner, Louisiana, as the primary contractor for the Chapel project. The choice was based primarily on BLD’s products for lateral rehab and its extensive experience with installations. Any remaining mainline CIPP, manhole rehabilitation or excavations were set to be handled by BLD’s chosen subcontractors.

To reline the laterals in the Chapel basin, BLD used its proprietary product, Service Connection Seal + Lateral (SCS+L). It’s a full-wrap liner with hydrophilic material in the main that expands in the presence of water to eliminate infiltration at the connection point. The BLD SCS+L is an ambient cure product, and installations were performed from the main without the need for crews to have access to a clean-out or create a secondary access point.

This combination-style trenchless CIPP lining product provided a watertight seal at the lateral interface with the mainline to mitigate infiltration at the connection and become a jointless CIPP liner to structurally replace the lateral host pipe if needed.

An eye-opening experience

The Chapel project demonstrates the advantages of an all-inclusive approach instead of the methods used in the county’s early program from 1996 to 2006. During that time, the county performed large amounts of lining but continued to experience unexpected I&I from its laterals.

There was a lack of focus on removing abandoned service connections during that period as well, and technology like lateral-launch cameras weren’t yet available. The county didn’t have the manpower to track down abandoned service connections or perform smoke and/or dye tests to determine which laterals were active.

“As we were performing CIPP lining on the mains, we were addressing structural issues; but when they were reinstated, we were simply connecting infiltration points back into the system in the rehabilitated mainline,” Powell says.

During the Chapel project, it was discovered that a high percentage of the service connections were actually inactive, so these were plugged off and patched. Active service lines were rehabilitated by BLD with the SCS+L lining, and manholes were also rehabilitated.

“Our goal with the Chapel project was to make the whole area and all of the elements in the system watertight, eliminating all I&I possible,” Powell says.

But performing the work and remaining hopeful is not enough for the county or Hazen and Sawyer. They need to know for certain that the efforts they make are in fact successful. Using the information from their modeling, once an area is completely rehabilitated, flowmeters are set up as control meters to measure the actual flow. Following this is a small regression analysis to determine what the volume reduction is and what the peak flow reduction level has reached.

“Because we are using similar rainfall before the rehab was performed and comparing it to after the rehab is complete, we are able to compare apples to apples, pre- and post-flow monitoring accurately,” King says.

If a remediation is not performing as well as expected, the county may opt to not wait for rain events to determine model flows and instead will perform quick field evaluations. For example, the county would choose 10 manholes in an isolated area for manual examination and, if necessary, make needed repairs to an area where I&I has migrated.

The county quickly acknowledged that approaching I&I mitigation projects as it did with the Chapel project demonstrated just how effective a comprehensive rehab is versus looking at capacity improvement projects as the only alternative.

Peak flow challenges

Jefferson County’s largest challenge is peak flows induced by weather. These wet-weather events continue to create stress at the county’s treatment plant, pump stations and even as far along as customers’ homes.

During heavy wet-weather events, customers were affected so severely that they would not be able to operate washing machines unless they removed the clean-out cap on their property. This is where sewer modeling assisted the county in addressing its entire system. Jefferson County modeled its entire system (pipes greater than 8 inches in diameter and critical 8-inch pipes), basing its design on a two-year, 24-hour storm. This allowed the county to accurately pinpoint where its most severe problem areas were located.

“We found that we could have great success, and the modeling and optimizing changed the way we began to look at future work,” White says. “Traditional engineering says build a bigger pipe, move the water downstream or build storage, but we found we can get enough water out of the system through these new I&I-reduction methods to reclaim capacity, move the water and experience success at a lower cost.”

Between the modeling, post-project quality control, optimizing analysis and comprehensive approach, the county has a solid road map for maintaining its system cost-effectively and long into the future. “I believe, for the first time, we as system owners know where our problems are,” White says. “We have the planning tools to forecast what it’s going to take in terms of work and cost to eliminate the problems and truly achieve success.

“With Hazen and Sawyer’s tested design approaches and solid, reliable technology products from contractors like BLD, we can achieve our I&I reduction goals and get the extra capacity we need, all at a lower cost, making us good stewards of public money. It’s rewarding to know we’re making good investments and the community now will have a sewer system that’s reliable and effective.” 



Discussion

Comments on this site are submitted by users and are not endorsed by nor do they reflect the views or opinions of COLE Publishing, Inc. Comments are moderated before being posted.