STORM: A Downhill Battle

The City of Duluth battles topography and cold winters in a campaign to manage stormwater and comply with national guidelines

One look at the topography of Duluth, Minn., and you understand­ the challenges facing the city’s stormwater management team.

Developed as a long, narrow strip against a ridge overlooking Lake Superior, Duluth features a steep drop of more than 880 feet from the top of Thompson Hill, its highest point, to the water’s edge. The velocity of stormwater as it rushes downhill, plus the area’s clay soil, can result in serious erosion, according to Chris Kleist, stormwater project coordinator.

And then there’s winter. Temp-eratures can plummet to 40 degrees F below zero, and frost depths of 6 to 8 feet or more are not uncommon. These conditions burst pipes, freeze streams solid, and ice up catch basins and other stormwater infrastructure.

“Plus, a lot of the city is built on bedrock, so the frost can really be a problem, and water main breaks contribute to the storm flows,” says Steve Lipinski, utility operations manager.

Despite these obstacles, the team is making a comprehensive effort to comply with Phase II national stormwater guidelines by improving the infrastructure and involving the public in stormwater management, especially through an award-winning Web site.

An appreciation for clean water in this part of the country helps. “We have a high quality of water here,” Kleist says. “That includes 12 designated trout streams and another 31 named streams in the city, many unnamed streams, plus Lake Superior, the largest freshwater body in the world and the most pristine of the Great Lakes. People just need to look out their window to see clean water.” A tenacious program of catch basin cleaning, culvert deicing and stream maintenance also helps.

The old days

It wasn’t always this way. Duluth put down footings in 1856 as a vital port city at the western tip of the Great Lakes. Its storm sewers date from about 1880, when officials piped some of the city’s many creeks to allow development up the hillside and along the lakeshore.

Most storm sewers are made of reinforced concrete pipe (RCP), clay tile and corrugated metal pipe. However, a few were wooden pipes, and brick arch tunnels served to channelize the streams and discharge stormwater runoff directly to Lake Superior. “Before 1998, we didn’t focus our attention on the stormwater system,” says Todd Carlson, a water-quality specialist. “In fact, our maintenance program consisted pretty much of emergency repairs.”

Today, things are much different. The last known wooden pipes came out of the ground in 2006, and all have been replaced with RCP or metal pipe. And since the implementation of the National Stormwater Management Program, Duluth has set an exemplary pace in developing and applying best management practices (BMPs) for stormwater management.

In a key development, the city organized a separate stormwater utility within its Public Works division. “We developed a stormwater utility in 1998 to address operations and maintenance issues, in addition to providing funding to deal with water-quality issues and comply with NPDES Phase II rules,” says Lipinski.

The stormwater utility staff includes a manager, supervisor, engineer, project coordinator, two water-quality specialists, clerical staff, and maintenance, construction and CCTV crews.

An area-wide Regional Storm-water Protection Team (RSPT) meets regularly to share technical expertise and develop common educational materials. The team includes 26 Minnesota and Wisconsin shoreline communities; local, state and tribal resource and regulatory agencies; and university educators and researchers. All share an interest in the welfare of Lake Superior and its tributaries. The team has developed more than 60 BMPs for stormwater control.

The utility is also collaborating with the University of Minnesota-Duluth to determine how much runoff can be eliminated by retrofitting homes with BMPs. The study is funded by an EPA 319 (Nonpoint Source) grant that will directly compare runoff from a “treatment” neighborhood to a nearby “control” neighborhood over several years.

See it now

The area’s stormwater management program is best illustrated on its Web site at www.lakesuperior It was created by a group of educators and researchers at the University of Minnesota-Duluth (UMD) Natural Resources Research Institute (NRRI) and Minnesota Sea Grant College, working in collaboration with Duluth’s stormwater utility, the Western Lake Superior Sanitary District, and the Minnesota Pollution Control Agency.

EPA funding initiated the project, and National Oceanographic and Atmospheric Administration (NOAA) Coastal Program grants have helped keep it alive and dynamic since 2005, as it has grown to encompass the north and south shores of Lake Superior.

“A bunch of us at UMD were involved — aquatic and watershed ecologists, and science educators who were using real-time data collected remotely from lakes and streams to help people under-stand how these water bodies work and how to keep them healthy,” says Rich Axler of NRRI, one of the site’s creators.

The site is rich in content, easy to use and designed with the stormwater utility’s diverse audiences in mind. For example, in fulfillment of the Phase II public education and public outreach requirements, homeowners, students, opinion leaders and others can find a multitude of useful information in the “Understanding” section:

• Tips and tutorials on rain barrels, lawn care and other “green” solutions.

• Case studies on how to slow water down and keep it clean.

• Things anyone can do to decrease runoff and erosion.

Builders and contractors, too, find information that ­helps them comply with the Phase II construction site and post-construction provisions, including contractor training information, how to create stormwater management plans, example stormwater ordinances, a tool kit of BMPs, and requirements for erosion control.

“We’ve had good acceptance among contractors,” Carlson notes. As an example, the utility staff designed a template for contractors to stamp into concrete catch basin forms that tells people not to dump waste into them. “It was a one-time thing, but now all contractors use the templates when they do street reconstruction,” says Lipinski.

To bring illicit discharges to the public’s attention, the site includes an interactive demonstration of illicit discharges and examples of good and bad practices. It also introduces the utility’s “team of illicit discharge detectives.”

Axler reports that site use is growing and averaged more than 400,000 requests per month in 2008. Site visitors come from more than 100 countries, and many schools and students use it. “We see large traffic increases in the spring and fall when school and university classes are in session,” Axler says.

Cleaning and steaming

Duluth’s rigorous program of cleaning and deicing stormwater infrastructure may have been its most effective BMP. The goal of the department is to clean the entire stormwater collection system every eight to 10 years, but the city’s unique terrain and temperatures result in much more frequent maintenance “as needed.”

A fleet of four Vactor 2100 series trucks and a Vactor hydro-excavator, all from Vactor Manufacturing, help clean storm drains and the more than 9,000 catch basins in the system. Upon receiving a work order, the stormwater crew pulls the grate and vacuums and flushes the line. They work back from the line to the manhole so they don’t have to block the intersection.

Duluth’s team inspects all 17 sedimentation basins every year and cleans them when required. “It’s a fairly intensive program, because we have several different types of basins,” says Kleist. For vortex chamber basins, maintenance workers pull the manhole lid and use a Vactor unit to clean out the center section of the basin.

“One of these is below the level of the lake,” explains Carlson. “We close it off with hurricane doors and dewater it with a 6-inch pump. Then we use a vacuum truck to take out floatables and sediment.”

For square cistern basins with baffles, crews use a construction excavator to remove debris and sediment. Duluth also maintains open-channel basins, several hundred yards long, paralleling the expressways. Front-end loaders drive into the basins to scoop out sand and sediment. “It can take several days to do this,” says Kleist, “but these basins work really well.” Material removed from the basins is dried and tested to determine the proper disposal site.

Ice is another issue. To prevent it from blocking the system and causing flooding, the city has an impressive deicing program. The crew uses three Hydro Tek SC32007KQ steamers and one truck-mounted Hydro Tek unit from Hydro Tek Systems Inc., each capable of heating water to more than 200 degrees F and producing 3,200 psi. The units can clear a 15-inch culvert, frozen solid top to bottom and end to end, in minutes.

For ice-ups in difficult terrain, the crew uses an HS 41 Spider “walking excavator,” manufactured in Germany by the Schaeff Co. “It walks on telescoping legs, and it works extremely well on very steep slopes and uneven terrain,” Kleist observes. “It has a gentle footprint and leaves very little disturbance on sensitive stream banks and hillsides.” The machine can be operated safely on a one-to-one slope and can walk through water up to 5 feet deep.

Public acceptance

Duluth and the rest of the RSPT partners believe it makes more sense to protect existing water quality than to pay to clean it up later, and that public education is critical, especially as funds become more and more scarce.

The city bills a stormwater utility fee of $6.08 per equivalent residential unit per month and bills commercial developments based on their amount of imper-vious surface, with credits for approved BMPs. “There are never enough dollars to do everything that needs to be done,” says Kleist, “but it ultimately depends on how much the public wants to spend, and what level of service they are willing to accept.

“We’re playing catch up, but we’re gaining on it.”


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.