Published July 2007

Staying Ahead

By Mary Shafer (page 26)

The City of Auburn, Ala., tackles two major runoff mitigation projects in pursuit of EPA Phase II stormwater compliance.

As one of the fastest growing cities in its area of Alabama, the City of Auburn faces increasing pressure on its storm and sanitary sewer systems.

“As a whole,” says water resources management director Scott Cummings, “our two top challenges are water supply and wastewater collection and treatment. We’re not on a major waterway, so our supply is somewhat limited. The resources are there, but the problem is evaluating the best methods for collecting and distributing them.”

Auburn’s stormwater challenge is to maintain water quality in area streams so that development is not a detriment to them. Development is abundant in the city’s locale between Montgomery, Ala., and Atlanta, Ga.

As a state-designated Municipal Separate Storm Sewer System (MS4), the city is required under the EPA’s 2003 Storm Water Phase II rule to obtain an NPDES permit and to develop a stormwater management program.

The city water management team works hard to stay in compliance. Watershed division manager Matt Dunn works with Cummings, assistant city engineer Brett Peterson, and civil engineer Bryan Wood to meet federal requirements, while addressing storm-caused flooding, managing the city’s two wastewater treatment plants, and trying to anticipate the needs of non-stop development.

Two new stormwater projects — in the Country Circle and Heartstrings developments — address specific issues related to the stormwater plan. Country Circle addressed residential flooding, while Heartstrings brought an industrial park up to Phase II standards for handling runoff in preparation for development.

Flooding mitigation

“Country Circle was identified as a problem area because we had some flooding of residences there in 2002-03,” explains Peterson. “It’s an older area of town that didn’t have a lot of conveyance infrastructure, and we had to mitigate incorrect ground slope there. We applied for FEMA flood mitigation funding, and were awarded the money to install 750 feet of 24-inch reinforced concrete pipe (RCP) or high-density polyethylene (HDPE).” The low bidder, Auburn’s own M&M Materials, came in with RCP.

“In addition, we replaced four inlets along this run of pipe and upgraded two existing inlets to double-wing models to meet our current standards. The project actually had several unique points to it. One was that we’re running parallel to an old terra cotta sanitary sewer line, and had to cross it in two locations. We had to pay special attention to that. We went through and televised the line to determine location.”

Workers removed two, 4-foot lengths of the sanitary sewer and replaced it with ductile iron. “When we’re done laying pipe,” Peterson says, “we’ll go back and re-inspect the sanitary sewer to make sure the new construction wasn’t detrimental to it. If we feel any pipe crossings were compromised, we may need to come back with some CIPP work to make repairs. We’ll remove three joints of the clay pipe and replace it with a section of ductile iron at the cross.” The contractor has already completed inspections and digging.

Four affected property owners have large animals that had to be accommodated in the back yards during the work, so the contractor installed temporary fences. With this preliminary work out of the way, about 25 percent of the pipe-laying was completed as of spring 2007.

Pre-inspection and planning

Actual site walking drove careful planning that paid off handsomely in the Country Circle project. Even the homeowner-pleasing aspects of the job “didn’t put us too far behind schedule,” says Peterson.

“We had done a good job of staying in touch with homeowners and accounted for that work up front to keep it on schedule and within budget. We were originally scheduled for 90 days, beginning in March. The bid came in at $120,785, and our preliminary cost estimates were within a thousand dollars of that bid.”

What did threaten to undo the schedule was an unexpected technical issue. The planners had worked closely with the local electric company to help locate its utility lines in the right-of-way, but the ones that caused problems were outside the right-of-way. “We found the electric company had gotten a little creative in how they had located their underground service,” Peterson recalls.

“When their lines crossed some of the yards, they ran parallel with the road outside the right-of-way, instead of taking a more direct path from the transformer to the house. We were forced to run high to accommodate a reasonable amount of cover over the existing pipe, but still not protrude.”

Wood, who acted as project manager, says, “We were also trying to avoid sanitary sewer utilities and the indigenous slope of the ground there. Grades became critical: We had to go to 12-inch by 28-inch elliptical concrete arch pipe to accommodate grade.”

The city also had to acquire an easement along the backs of six properties to avoid the sanitary lines. The staff acquired those within three months of establishing first contact with homeowners.

The last challenge in this older area of Auburn was mature trees. Several larger ones on private property had to be removed. The team anticipated resistance from homeowners, but Peterson says, “They were actually excited enough that we were addressing their flooding problems, that most people were OK with it. A few property owners wanted us to replace the trees elsewhere, so we did.”

Industrial area preparation

The Heartstrings project involved mitigation of 270 feet of stream in the city’s industrial park to current Phase II standards, so that the site’s collection infrastructure could support future development. It involved installation of 205 feet of 36-inch RCP, along with two grate inlets and one headwall, by the Hudmon Construction Co. of Opelika. The project’s budget was $40,868.

“It was a pretty straightforward job,” says Peterson, “but we had to purchase a stream credit from the U.S. Army Corps of Engineers.” Federal law requires that any disturbance of a perennial or intermittent stream be met with onsite mitigation — rehabilitating a stream bank or channel and stabilizing it with wetland riparian plantings — or with the purchase of stream credits that allow the rehabilitation to be skipped.

“Our policy is to make every effort to use bottomless culverts and other tools to make as little environmental impact as possible,” Peterson explains. “The actual parcel of land wasn’t large enough to support onsite mitigation, so our only option was to purchase stream credits.”

Dunn adds, “Credits are extremely expensive, so it’s to our advantage to opt for onsite mitigation when possible.” The project was completed on time, within the 30-day schedule, on April 11.

Treatment challenges

On the wastewater side, inflow and infiltration is increasingly important for Auburn, mainly because much of its infrastructure is aging. “Some of our lines are 40 to 50 years old,” says Dunn. “We’ve noticed a lot of I&I on some of our main interceptor lines. Right now, we have a consultant putting together a scope of services report on one of the main interceptor lines that goes into our Northside treatment plant.

“We’re looking at options for building new facilities and purchasing treatment capacity from the neighboring City of Opelika. Right now, we’re in the process of determining what’s most cost-effective.”

Meanwhile, the city must make sure to stay ahead of growth. Part of that effort includes removing extraneous flows from the system, and sharing flows between the city’s two wastewater treatment plants. In 2005, the city approved a Wastewater Treatment and Disposal Master Plan, developed by consultants CH2M Hill. The plan includes an evaluation of the treatment plants and recommends capacity upgrades.

Proactive approach

In dealing with I&I issues, the Auburn team has gravitated toward less disruptive repairs. In fact, the overall approach has become “much more creative,” according to Peterson, especially in dealing with rehabilitation projects looming on the horizon.

“While we were waiting for the storm drain projects to mobilize, we were able to complete a 60-inch sanitary line rehab,” says Peterson. “The metal pipe had deteriorated under one of our major thoroughfares, and we were losing road material. We brought in Reynolds Inliner LLC of Bessemer to do CIPP trenchless on it.

“While they were in town, we also had them do 50 feet of 18-inch metal storm drain pipe and about 300 feet of 8-inch sanitary sewer on College Street. We had them come back a second time to address 505 feet of 24-inch unreinforced concrete sanitary pipe that had been in the ground 50-plus years.”

When team members specify liners on such jobs, they call for H20 standard, which not only seals the pipe but adds to the structural strength to meet current standards, “all without having to dig up the road and annoy our citizens,” says Peterson.

It’s a delicate balancing act performed on a daily basis by the Auburn water management team, and the outlook is good. Practice, as they say, makes perfect.