Battle of the Blockage

Armed with a targeted preventive maintenance plan, the Cedar Rapids Sewer Maintenance Division campaigns against sanitary sewer backups

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The City of Cedar Rapids has reduced sanitary sewer backups by more than 80 percent — proof that its aggressive war on blockages is working.


The Sewer Maintenance Division’s key weapons against blockages include a comprehensive preventive maintenance program (PMP) and a targeted capital improvement program (CIP) to upgrade the infrastructure.


Cedar Rapids has a population of 125,000, but it has a large industrial base. The wastewater flow is 30 mgd, more typical of a city of 1.2 million. For years, the city took a reactive approach to blockages, which occurred at the rate of 500 to 700 per year.


No longer willing to accept the service interruptions and high costs and risks of blockages, the city implemented a mandatory grease trap program in 1994. As county and building inspection teams enforced those rules, backups dropped to 120 by 2003.


“In that year, we implemented our PMP and CIP and reduced sewer blockages by 60 percent in three years,” says Public Works maintenance manager Craig Hanson, P.E. “These programs have also helped decrease the average flow of wastewater to our treatment plant by almost 15 percent and peak flow by 25 percent.


“We accomplished this by combining several tools and technologies. Our PMP uses geospatial technologies, work order management, and CCTV pipe inspection to provide us with accurate information on the location and condition of our sanitary sewer pipes. Our CIP involves rehabilitation of more than 25,000 feet of line with cured-in-place liner and replacement of over 5,000 feet each year.”


Building a database

The Cedar Rapids sanitary sewer system serves a population of about 155,000, including residents of Marion, Hiawatha and Robins, part of Fairfax, and a small portion of Linn County. The 31 members of the Sewer Maintenance Division operate and maintain the sanitary and storm sewer systems. The city maintains more than 650 miles of sanitary sewer pipes in sizes from 6 to ­96 inches with an average age of 53 years. The Water Pollution Control Department takes care of the system’s six lift stations.

“Although the system is simple, it takes careful review and coordination to ensure that more than 1,300 annual preventive maintenance actions are completed and documented,” Hanson says.


In fighting any battle, it is critical to know the geography and history of the battlefield. In Cedar Rapids, a geographic information system (GIS) supplies the geography, and a work order management system provides the history.


In 2004, the Sewer Maintenance Division performed a thorough review of the previous three-year period to locate sites of backups and document past cleaning efforts. The team then inspected each location to identify specific pipe defects. This helped them build a database of nearly 1,000 locations. Since then, crews regularly review work orders from inspections and blockage responses and enter more information into the database. That has added 300 more locations.


The GIS provides an inventory of pipes and structures. Global positioning systems (GPS) are used for accurate field-data collection and condition analysis. The GIS was developed 10 years ago using ESRI shape files, and the staff has refined it over the last five years into a robust enterprise Geodatabase.


The city began using a Sokkia survey-grade GPS for data collection in 2002, and also uses recreational-grade and GIS-grade GPS units for locating and other data-collection tasks. New sewers are located with GPS and entered into the GIS along with attribute data, such as elevations, diameter, material, and project number. Data for existing sewers is field verified using GPS and, if necessary, revised in the GIS.


Work order management

“The work order management system we use was developed by GBA Master Series Inc. and allows us to track, manage, and analyze the work performed on our sewer pipes,” Hanson says. “We can categorize and summarize this work based on cause (such as roots or grease), tasks (inspecting or cleaning), personnel, and equipment. All staff time is tracked in the work order system to provide cost-of-service data.


“One of the keys to our work order management system is that we record work data by each pipe segment, as opposed to an address or a general street location. The work data can then be linked to the GIS to provide a method to call up each pipe segment and look at its history.”


The city’s inspection program is a systematic and proactive effort to document pipe conditions. GIS information on pipe diameter and age helps the staff target areas with older and smaller pipes that are more likely to have blockages. The work order management system helps identify problem areas based on customer requests.


Most televising simply verifies that pipes are functioning properly. Where televising finds problems such as roots, grease, or debris, the lines are cleaned using four Camel sewer and catch basin cleaners from Super Products LLC, three with 11-cubic-yard debris bodies and one with a 16-cubic-yard tank. Once cleaned, the pipes are then added to the preventive maintenance database.


Depending on the problem and its severity, routine maintenance work orders are created to revisit those pipes every three to 24 months for cleaning. Where televising identifies significant problems, such as severe recurring roots or broken pipes, those pipes are added to the database of pipes to be lined or replaced.


In addition, the city inspects sewers in new developments before accepting the maintenance bond to verify that pipes are installed to city standards and are functioning properly. To inspect interceptor sewers (60 to 90 inches), city crew members use a QuickView XR pole camera (Envirosight LLC) with zoom capability to look down the lines and assess general conditions, such as debris and corrosion. More detailed interceptor inspections are contracted as needed.


The televising program is supported by four vehicles. Two vans have Pearpoint Inc. cameras and tractors, which provide detailed inspection. Two combination jetting and camera trucks, one from Super Products and one from PipeHunter, are used for quick verification of pipe conditions.


Capital improvement

The city also aggressively targets repairs to lines that need more than cleaning. Sewers with severe structural defects, such as collapsed or broken pipes, are given priority, and city construction crews often repair them immediately. Pipes with less serious structural defects or with severe recurring root intrusion are added to the CIP database for future work. Pipes with the most severe root problems are typically lined in the next fiscal year.


In addition to reducing blockages, the lining and pipe replacement program reduces infiltration and inflow.

“Since we track our work based on staff hours and by pipe segment, we can use this data to see outcomes and show historic trends as well as determine future financial needs,” Hanson says. “Historically, we can show that our productivity is increasing by querying the total linear feet of pipe cleaned and televised over given periods of time.

“We can also show service increases and cost savings through the reduction of sewer blockages. For the future, we can analyze the historic data to help us determine what pipes will need attention and estimate the cost to do the work. Additionally, we can use this data to analyze comparisons. Currently, the City of Cedar Rapids experiences only 25 percent of the sewer blockages seen by an average city of similar size.


“Although the individual tasks that make up our PMP had been performed for several years, 2003 was the first year that they were all put together into a dedicated and definable system. Since then, we have experienced tremendous improvement in service level and productivity.”


It just goes to show what happens when you go to war with the right people, the right equipment, and a well-designed plan of attack.


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