Wednesday, August 14, 2013
Sarah Ferdico, Communications
Sanitary sewer systems can be incredibly frustrating. We need them for our daily lives to function smoothly, but they are buried deep in the ground beneath our residential roads, highways, gorgeous mature trees, and lovingly landscaped yards. Many communities have older sanitary sewer systems made of vitrified clay and concrete pipes that corrode, crack, and become filled with tree roots and other debris. These older systems are also prone to increasing amounts of infiltration that enter the sanitary sewer system.
Fixing these systems with traditional open-cut methods would result in bringing in heavy equipment and excavating the area. This method can be inconvenient, invasive, expensive, and unsightly. A much less intrusive option for sewer rehabilitation is incorporating trenchless technologies.
Olsson Associates’ engineers have been gaining and using detailed knowledge of current trenchless sewer rehabilitation techniques that circumvent the need to tear up large areas of ground. Using trenchless technology, sanitary sewer pipes can be rehabilitated with minimal or no digging at all. This technology includes the following techniques:
Olsson has also found value in semi-trenchless technologies such as “pipe bursting,” which allows full pipeline replacement and upsizing of existing sewer lines. It also reduces excavation and surface disruption.
Olsson has developed detailed specifications and bidding documents for these trenchless sewer rehab techniques. Olsson also provides assistance conveying specifications for cleaning pipes and providing video inspection of sewer lines and manholes. Olsson also monitors flow and rainfall conveyed through sewer systems, conducts smoke and dye testing, and provides protocols and systems for managing the large amount of data generated.
Because they are diligent in being up-to-date on the current trenchless rehab technologies, Olsson staff members can recommend several options for solutions after performing a collection system analysis. These options include a sanitary sewer evaluation study, a bypass elimination plan, or an inflow and infiltration reduction/elimination study.
Below are examples of how Olsson is helping communities in Nebraska, Colorado, and Missouri rehabilitate their sanitary sewer systems with minimal disruptions.
Olsson’s Missouri offices are currently working in several Missouri communities to bid and construct significant sanitary sewer rehabilitation projects, including projects in the cities of Buffalo, Humansville, and Sedalia.
Buffalo, Missouri, is a quaint community of 3,100 residents with a town square surrounded by businesses and residences. Beneath the town square is an antiquated clay-pipe sewer system that would be costly and disruptive to repair with traditional open-cut methods. Buffalo has an EPA Consent Order to significantly reduce the system’s inflow and infiltration. Olsson reviewed video of 30,000 feet of sanitary sewer pipe and determined that about 10 percent of the pipe needed to be rehabilitated. Olsson recommended a series of repairs that included manhole-to-manhole CIPP liners, CIP point repairs for smaller sections of deficient sewer line, and CIP lateral connection repairs to fix problems with service lines connecting into the mainline.
Humansville, Missouri, is a town of 1,100 people. City officials contracted with Olsson to develop a significant collection system rehabilitation project to reduce excess inflow and infiltration to allow its current wastewater treatment facility to meet effluent discharge limits. Olsson reviewed video of the entire Humansville collection system, which included about 40,000 feet of clay pipe. It was determined that much of the clay pipe was in poor condition and mostly located beneath paved areas or in narrow alleyways along residential backyards. Using trenchless technology turned out to be an ideal way to address Humansville’s extensive sanitary sewer needs while minimizing disruption to the community.
For both Buffalo and Humansville, construction is expected throughout 2014.
Sedalia, Missouri, home of the Missouri State Fair, needed to come into compliance with the Missouri Clean Water Law and correct inadequate facilities to address wet weather flows throughout the city’s system. These flows typically resulted in overflows and backups in the collection system and bypassed the city’s three wastewater treatment plants. Project challenges in the community included two major highways and several railroad tracks to work around. Deep sewers in narrow downtown alleys also presented significant challenges and costs for conventional construction techniques that trenchless technologies avoided.
Olsson helped develop and implement a $30 million, seven-year program of improvements to Sedalia’s wastewater facilities. A significant element of the program is comprehensive rehabilitation to the sanitary sewer collection system. This rehab consists of repairing over 900,000 lineal feet of pipe, a large portion consisting of vitrified clay pipe and brick manholes.
A multiphase plan was developed based on prioritized rehabilitation to remove sources of direct stormwater inflow. The plan also prioritized structural rehabilitation to reduce infiltration. The next phase of improvements will include rehabilitating approximately 50,000 lineal feet of sewer main. Construction will use a combination of conventional and trenchless rehabilitation and replacement techniques.
Kevin Waldron, PE, lead engineer on the project, estimates that one-third of the sanitary sewer problems will be resolved with trenchless technology.
“Trenchless technology is important because we need a variety of tools to address a wide range of circumstances,” said Kevin. “Trenchless technology gives us the tools we need to address the challenges of working around railroads, highways, and space-restricted areas.”
Olsson is currently in the process of developing final construction documents for phase one rehabilitation work on Sedalia’s facilities.
In Colorado, trenchless technology was used to maintain the historic beauty of the tree-lined University of Colorado Boulder campus. A 450-foot sewer line next to the 120-year-old Hale Science Building and Varsity Lake had become cracked with age. Traditional fixes would have included digging up hundreds of feet of landscaping, bringing in an excavator, closing down premium parking, and potentially losing mature trees. Olsson reviewed video data of the existing pipe’s interior and offered an alternative recommendation to conventional open/cut methods: trenchless technology. Olsson determined that, since the sewer line had only minor cracking and small root intrusions, trenchless technology was a good option. Using trenchless technology to fix the pipe would leave landscape intact, preserve trees and other landscaping, keep parking open, and allow workers to complete the project in a day. In addition, the cost of the trenchless option would be less expensive than traditional excavation and pipe replacement.
University officials agreed with the trenchless approach, and Olsson moved forward with the design for implementation. To resolve the sewer repair needs, a CIPP liner was threaded through the existing pipe and cured. CIPP liners can then be cured using steam, water, or ultra-violet light. Once the CIPP liner is cured, it functions as a sturdy, new pipe inside the original pipe.
“This would have been a very messy, invasive, and more expensive project if it had been fixed using traditional methods,” said Megan Orloff, project engineer. “The condition of the existing pipe and the site constraints made it a natural candidate for a trenchless solution.”
In Nebraska, the City of Grand Island had two separate challenges. First, the south and west interceptor sewer lines needed to be evaluated. Olsson used video technology to grade each section of these interceptors. An “A” grade meant the line was in the best condition. An “F” grade meant it was in the worst condition. Areas with grades “D” and “F” were prioritized for rehabilitation with nearly 2,500 feet of sewer pipe identified for rehabilitation.
The characteristics of the south and west interceptors clearly illustrated the benefit of trenchless repair. The lower end of the south line is largely residential, while the upper end is mostly commercial. A major roadway called South Locust Street also crosses this sewer line. The west interceptor crosses through Burdick Power Station and the Burlington Northern Railroad, which is a double rail line. Given the presence of residential and business areas, a power station, and railroad tracks, trenchless technologies allowed the sewer lines to be repaired with only a fraction of the disruption and complications that would have arisen from traditional excavating.
A second project in Grand Island was located along the 5th Street sewer line. The existing system was made of vitrified clay pipe located in a 16-foot-wide alley along a heavy business and residential area with 160 services tied into the system. Olsson used video to determine the pipe’s condition and to locate all the service entry points. The pipe was cleaned out, and targeted spot-digging was done to address areas of the existing pipe that were too damaged to install a CIPP liner. Once those areas were addressed, a CIPP liner was used along the length of the system. A remote-controlled cutting head was then used to go back into the newly cured pipe and re-cut the pipe to reconnect the 160 service points back into the system. The result was a rehabilitated sewer system with minimal disruption to the businesses and residences served by the 5th Street sewer line.
Communities want their sanitary systems to function smoothly. Unless absolutely necessary, repairs should not be overly disruptive to residents and businesses. Olsson is working continuously to offer the latest technology to our clients so that a full range of options for rehabilitation are available. For more information, please contact Mike Yost at 303.237.2072 or email@example.com.