Bringing It All Together

St. Louis MSD takes on a large-scale revamp of a sprawling collection system that dates to the Civil War era.
Bringing It All Together
The Metropolitan St. Louis Sewer District team includes, front row, from left, construction laborer Frank Coleman, operations supervisor Chris Patrick, and assistant operations supervisor Mike McDowell. Back row, collection system team leader Gregg Hall, collection system operator Jonny Welch and collection system operator Dan Kateman.

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So how does a sewer district that once consisted of 79 different systems in 91 separate communities and has pipes up to 150 years old eliminate hundreds of combined and sanitary sewer overflows and basement backups while staying on schedule and complying with a consent decree in the process?

The Metropolitan St. Louis, Mo., Sewer District (MSD) is staying centered on their management plan, engaging the community, using a range of technologies — both gray and green — and doing maintenance around the clock.

MSD is working on the first phase of a multi-decade, $4.7 billion capital improvement and replacement program to update and rehabilitate its aging collections and treatment system — one of the nation's largest and most complex. Over the last 20 years, MSD has invested over $2.5 billion to remove more than 350 overflows from its system; the current phase of the project will address the remaining 350+ overflows over the next two decades. In addition, MSD is rehabilitating interceptors, pump stations and force mains, and making improvements to its wastewater treatment plants.

"The original sewer system was built separately over the years," says Brian Hoelscher, MSD's director of engineering, describing a series of smaller independent networks that developed as the metro area grew before the creation of the MSD in 1954. "We probably have a lot of smaller pipe sizes and more footage than you'd find elsewhere, and that defines cost. Our trunk system is not well laid-out. It's our biggest technical challenge."

Background

MSD is the fourth largest sewer district in the United States, serving over 1.3 million people residing in the City of St. Louis and about 80 percent of surrounding St. Louis County — a total of 525 square miles. The district maintains approximately 425,000 residential and commercial accounts, and operates 9,700 miles of combined, sanitary and storm sewers, 275 pump stations, and seven wastewater treatment plants that treat a combined average of 370 million gallons a day. A few of the sewers in the central city area date to the 1850s and are constructed of brick, clay and even wood in some places. "About 70 percent of our lines are 12-inch or smaller pipe, and some of what we call 'horseshoe' sewers are up to 20 feet in diameter," says Hoelscher.

Starting in the early 1990s — and after decades of work to consolidate dozens of small treatment plants into larger regional facilities, construct large trunk sewers to help integrate 79 sewer systems, and other efforts to ensure treatment of all flows during dry weather — MSD began to keenly focus on overflows.

In 2007, the State of Missouri and the U.S. Environmental Protection Agency filed a lawsuit against MSD resulting in a consent decree requiring MSD to spend $4.7 billion to address the remaining overflows and make other system improvements over the next 23 years.

"The current work is actually a continuation of the work we started back in the 1990s," explains Lance LeComb, MSD's manager of public information. "In the 2000s, we recognized the use of consent decrees by the EPA to address these types of issues nationally. Thus, we had already put processes in place and were ready to go when the lawsuit was filed. If anything, the consent decree shortens the schedule we had anticipated, but doesn't change much else for us."

Hoelscher says, in some ways, the consent decree actually serves as MSD's strategic plan for the next 23 years. "We stay very focused on it from an operational and capital expenditure standpoint," he says. "From there, we translate it back to our ratepayers so they understand where their dollars are going."

Construction and repairs

While MSD makes plans and finalizes designs to meet the regulatory requirements of the consent decree, St. Louis citizens are already benefiting from the results of the previous capital projects.

"Up to this point, we've been working on the overflows that are easy to get to — the low-hanging fruit if you will," says Hoelscher. "We started with well over 400 SSOs and we're down to fewer than 170. It's a continuous process for MSD, and we've been able to take care of basement backups, get rid of local surface discharges in yards and other areas where people can see standing overflow water. We've addressed debris and other unsightly conditions."

The work has involved remediating infiltration and inflow conditions — much of it in the old piping system MSD inherited — and enlarging pipe sizes to accommodate more capacity.

Wherever possible, St. Louis is relying on CIPP technology to line existing sewers, using a variety of local contractors. In other areas, "conventional dig" methods have been necessary. "In some situations, especially the brick pipe areas, we encounter collapsed sewers or sewers that have deteriorated to the point where they have to be completely replaced," explains Hoelscher. "We literally can't get our CCTV (closed circuit television) units through the pipe." Jonathon Sprague, MSD's director of operations, adds, "We do approximately two lining repairs for every one where we have to dig and replace."

Sprague estimates the district has been increasing the amount of trenchless lining work each year over the last 20 years. "In the early years, we were doing about $5 million in lining a year, but now that's up to about $20 million a year," he notes.

"CIPP has been very effective in taking care of structural concerns in the system," he adds. "Some of our I&I issues are actually caused by leaking storm sewers (alongside the sanitary lines). When we line the storm sewer, we eliminate the infiltration issues."

Another benefit of CIPP, he says, is the prevention of root intrusion and the backups that roots can cause. MSD identifies the sewer lines needing CIPP through the use of eight CUES CCTV units. MSD utilizes four of its CCTV trucks to perform proactive inspections, and the other four to investigate problems areas.

The district also operates two four-man internal CIP point repair crews, utilizing the Infrastructure Point Repair System from Infrastructure Repair Systems. Typical defect repairs include cave-ins, leaking joints, root intrusion and defective pipe, and each crew tries to complete two point repairs per day.

"The district typically utilizes the point repair system to repair defects in our sanitary s ewer system," says Sprague. "We keep a variety of point repair kits, from 2 feet to 8 feet for both cold weather and warm weather applications.

"We have embraced this technology not only because it is more cost effective than conventional open trench repair, but is also safer for personnel than working in a 15-foot trench, and less disruptive to neighborhoods and streets. Comparing costs, the district can make five or six CIP point repairs for the same price as one conventional open trench point repair."

In addition to sewers, MSD has been hard at it on the 162,000 manholes throughout the system. Sprague explains that the district takes a proactive approach. In the warmer weather, half a dozen four-man crews are out repairing defective manholes using the spin-casting spray lining technique. In colder weather, which is unsuitable for spraying, Sprague's team is divided into a dozen two-man crews devoted to manhole inspection.

Keeping it clean

As any collections system manager knows, keeping the system clean can be just as important as repairing and rebuilding the lines. St. Louis has adopted an aggressive maintenance and cleaning program, launched five years ago with the adoption of a comprehensive CMOM (Capacity, Management, Operation and Maintenance) program.

"Our mantra is clean, inspect, repair," says Sprague. "Fully 95 percent of our backups were on our 12-inch-or-under clay line. We have about 4,000 miles of that and so far we've cleaned all 4,000 miles, and we've started on our plastic pipe.

"We've cut basement backups by nearly 70 percent," he says, adding that dry weather overflows have been cut in half as well.

Sprague says the district uses cleaning to drive its inspection program. "When we clean, we use that occasion to do a rudimentary inspection. We record the amount and type of (materials) roots, grease or debris by inserting buckets and measuring how much material we get out."

Using Vactor rodder trucks, MSD cleans about 1,000 miles of sewer line each year, Sprague estimates.

Going forward

As St. Louis moves ahead with the next phase of its sewer improvement program — a public vote on a $945 million bond issue passed with 85 percent in favor last June — the district will employ both gray and green solutions to meet the new regulatory requirements and improve service to its ratepayers.

For CSO control, Hoelscher explains that the western and southern portions of the combined sewer area discharge to small streams that empty into the River des Peres, which ultimately flows to the Mississippi.

In this region, CSOs will be controlled through the construction of one main and two smaller deep tunnels. The main tunnel will be 28 feet in diameter and 8.97 miles long; the smaller ones will be 20 and 24 feet in diameter and 2.27 and 1.7 miles long, respectively. "The plan is to take stormwater overflow and direct it to the deep tunnel storage system, and then to treatment," explains Hoelscher. "Currently, the tunnel system is in geotechnical design. The plan is to start construction in about 10 years."

The rest of the MSD combined service area to the north and east discharges directly to the Mississippi, and here the district plans to employ a range of green solutions to control stormwater at its source.

"There are no open channels to the river," Hoelscher explains. "They've all been closed in with combined sewers. While the discharges already come close to meeting the secondary contact standards for the Mississippi, we want to mitigate the impact as best we can.

"We're planning to spend about $100 million on green solutions that capture the overflow water at its source, delaying it and preventing it from entering the river," he says. "Our goal is to reduce the overflow by at least 10 percent."

Among the techniques to be employed are rain gardens, green roofs, planter boxes, regional detention basins and permeable surfaces.

Key to success is a unique $3 million EPA-approved pilot project MSD is conducting to test the effectiveness of various natural solutions.

"In the northern part of our district, we have a great deal of lower income properties. Much of the property is owned by the city and is ripe for development," Hoelscher explains. "We're able to use these properties to demonstrate various forms of green infrastructure. In one case, we're looking at a whole block detention area. The response from residents and local entities has been encouraging."

Hoelscher says one organization that has been especially supportive is Habitat for Humanity. "They're excited about building green infrastructure into the properties they're rehabbing," he says.

In another phase, the district is buying up flood-prone homes and moving residents to comparable housing. The program improves the lots of homeowners while allowing the district to return the land to its natural state and improve flood abatement.

"We are working with partners, stakeholders. The pilot program enables us to see what projects work, which ones provide the biggest bang for the buck," Hoelscher says.

MSD plans to complete the pilot program and obtain the go-ahead to spend the $100 million from state and federal regulators by 2015. "Then we can really start cranking out some green infrastructure," Hoelscher says.

The people side

There's a very clear "people" side to the massive St. Louis project, one of the largest construction undertakings in the region's history. For one thing, the program means jobs and its completion will assure continued economic growth in the region.

For another, the project's managers need to have the community on their side as they spend public funds and drive construction through neighborhoods and backyards.

While the water quality regulations are paramount, Hoelscher and Sprague say that it's just as important that the public understand the district's watershed concept, especially the impact of stormwater. They say it's what people do at home that makes the difference, and it takes a lot of individual actions — everything from landscaping, to fertilizer, to household hazardous materials and pet waste.

While the consent decree provides marching orders, they say they have to change individual behavior, change the culture if they're going to be successful at developing these projects.

The plethora of small communities in the district can add to the challenge. "In some cases, we're in the backyard of a homeowner in one community, working on a sewer across the property line which is actually in another community," Sprague points out. "We need to communicate one-on-one ... that we're a team, we're one community."

Public information manager LeComb puts it this way: "Our main function is to provide a service to our ratepayers, whose sewer rates are going to increase every year for several years. They may not understand (the full scope of the consent decree work) but they may experience a basement backup first hand."

He says as the project eliminates these backups, customers can see that the program is working.

"We need to take advantage of the opportunity to show folks how we're spending money to build a true 21st century system," he says. "Not one that's rooted in the construction practices of the previous century."



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