New Paradigms

Innovations including a new cleaning and inspection system are vital to the City of Tacoma’s award-winning stormwater management program
New Paradigms
The Public Works team includes, from left, crew member Ryan Welander, chemist Rick Fuller, and crew member Troy Ihlen.

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Last May the City of Tacoma (Wash.) Public Works began an ambitious project to inspect the condition and sediment load in every foot of the city’s 10-inch or larger storm sewer pipes. That’s more than 2 million linear feet in all.

Using a combination of hydraulically powered equipment and wireless technology, the staff plans to finish the inspection in just four years. That’s at least 25 years faster than crews would need to do the job using conventional practices, according to Rick Fuller, a senior environmental specialist with the department’s surface water section. The inspection is also expected to cost one-fifth as much.

“In these times of increasing competition for utility funds, efficiencies like that are especially significant,” says Fuller, who is in charge of the inspection process, called the Stormwater Rapid Assessment Program (STRAP).

This project, the first of its kind in city history, is part of an asset management program to improve the efficiency of rehabilitating and replacing the stormwater conveyance system. Dating back more than a century, the system serves more than 66,000 surface water accounts in this Puget Sound community of nearly 200,000, located at the foot of Mount Rainer.

The system includes more than 11,000 manholes, 18,000 storm drains and more than 600 outfalls, some discharging into Commencement Bay, which forms the city’s deepwater port and much of its waterfront.

 

A new standard

As part of STRAP, Public Works has adopted technology developed in Germany to inspect municipal storm systems in Europe. Tacoma is the first city in the United States to use the Kleen-Vue system. It includes two digital cameras, operated by a water-powered generator and mounted on a water-propelled sled.

Images from the camera are transmitted wirelessly to a monitor, where the operator can view the pipe for cracks, breaks, root penetration and other defects or illicit connections. A two-person Tacoma crew has been able to inspect up to 3,000 linear feet of storm lines a day.

“This new approach to viewing pipes is a paradigm shift for us,” Fuller says. “We’ve been able to modify some of the same equipment we’ve been using in the past to handle the new technology. Now, we can inspect the pipe without having to clean it first and with minimal disturbance of any sediment in the pipe.

“It gives us a highly efficient and cost-effective way to get our eyes on the pipes. As a result, we’re no longer just reacting to an emergency and inspecting a pipe only when there’s a problem. Now, because of the economics, we can take a proactive approach and identify and fix areas that need attention before there’s a problem.”

 

Tracking contaminant levels

This isn’t the first time Public Works has taken steps to prevent rather than react to a stormwater management problem. For example, a multiyear project to clean up a contaminated channel that empties into Commencement Bay, the Foss Workplan (see sidebar), set the stage for continuing action to sustain the environmental improvements achieved by the project.

“The Foss Workplan started us down the path of extensive monitoring and responding to the results we found in addressing the quality of stormwater discharged into the waterway,” says Lorna Mauren, assistant division manager for the Stormwater Management Utility.

Her staff has expanded a program, begun a decade ago, to gather and analyze data about the sources and levels of contaminants in runoff and condition of the infrastructure. For example, water collected in storm drains and outfalls before and during rains is tested for contaminants and sediments. The information is used to improve control of point and nonpoint pollution sources and in retrofitting the pipes, catch basins, and stormwater ponds to better manage flows.

Meanwhile, the surface water section continues to monitor the waterway by testing chemical levels, conducting underwater surveys of channel conditions, and ensuring that habitat mitigation sites are working as they should.

“Not many jurisdictions have the kind of water-quality monitoring data and the ability to use this information in guiding efforts on the ground to improve water quality as we do,” Mauren says. “Over the past 10 years, we’ve seen some amazing results, including a 50 percent reduction in solids and an 80 percent reduction in polyaromatic hydrocarbons (PAH) in stormwater flowing into Commencement Bay.

“Our staff is very serious about preventing recontamination of the Foss waterway,” says Mauren. “They’re energetic, creative and excited about what they’re doing and the improvements we’re seeing in water quality. We have a lot of ideas.”

 

Spending money wisely

One idea the surface water section has acted on is its asset management program. Designed to help staff prioritize capital improvement projects, it divides the city’s storm system into 65 asset areas. Each is being evaluated on three critical aspects of stormwater management:

• Capacity to handle runoff effectively and prevent flooding

• Quality of stormwater runoff

• Condition of assets

The third factor is where Fuller’s team, STRAP and the Kleen-Vue pipe inspection technology come together. The surface water section is using the information collected by the pipe-scanning cameras to set maintenance and construction priorities. “We’re looking for where we should be spending our money to get the most bang for the buck,” adds Mauren. Engineers are using the Kleen-Vue system images to rate condition of the storm lines in terms of:

• Red (pipe has failed or needs immediate repair)

• Yellow (pipe has a root intrusion or other problem)

• Green (pipe is good)

“No one has viewed these pipes, some of which were installed 100 to 120 years ago, since they were first put in,” Fuller says. “We can’t afford to replace all 3.3 million linear feet of pipe. Sometimes that old pipe is working just fine, while lines no more than 30 years old may be failing. With this technology, we can find those parts of the system that are in the worst shape relatively quickly and fix them.”

To date, about 70 percent of the pipe inspected has been rated Green. “Some of the 100-year-old pipe is in great shape,” Fuller says.

 

System operation

Distributed in the U.S. by KEG Technologies, the Kleen-Vue system allows an operator to inspect a line and watch and record the process as it happens. Images from the two digital cameras are transmitted wirelessly as far as 980 feet to a receiver placed above a manhole.

From there, the images are sent to a monitor where the operator can view the pipe and use a keyboard to enter any additional information about the pipe’s condition. The images and any operator input are stored on an MP4 file. The city’s proprietary geospatial software is used to identify the locations of the images. The information can then be accessed online at various remote sites for analysis.

The Kleen-Vue system’s stainless steel sled is connected to a 1-inch high-pressure hose. Water flowing through eight jets propels the sled forward as it slides across any sediment in the pipe. “In some places, we’ve had to clean the pipe before we can send the Kleen-Vue unit through, but more than 90 percent of the time we don’t need to,” Fuller says.

“Also, because we’re using such low pressure and a small amount of water to operate the unit, any historical sediment in the pipe that we disturb travels only a short distance. That’s very important with our environmentally sensitive receiving waters.”

Public Works has worked with Sahlberg Equipment Company, a supplier of infrastructure maintenance and construction equipment, to acquire the Kleen-Vue system and adapt it to local needs. They have mounted the monitor/keyboard, the hose reel, the pump and a 700-gallon water tank on a trailer. The water tank can be filled using a hydrant or a water truck. At the 80 gpm flow used with the Tacoma unit, one tank of water provides eight to nine minutes of actual jetting time for operating the camera and sled.

 

Attractive economics

Fuller reports that his crew can inspect as much as 600 feet of pipe in eight minutes before reaching the end of the water hose. In the first six months of using this equipment, his crew inspected more than 200,000 linear feet of pipe.

Now that they’ve worked out all the kinks in operating and adjusting to the Kleen-Vue system, Fuller expects his crew to be able to inspect about 600,000 linear feet of pipe a year. The Kleen-Vue system and trailer setup cost about $200,000. Amortizing that expense over the life of the unit and including overhead, the cost of viewing the pipe is about 50 cents per foot.

“That low cost is the big ticket,” Fuller says. “In terms of asset management, this new system paid for itself in six months. That’s why we can be very proactive in our storm line maintenance program.”



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