Daily Progress

Daly City, Calif., pursues a rigorous schedule of sewer televising and repair, backed by a technological edge that is one part software, one part hardware

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When Bob Donati started working forthe Department of Water and Wastewater Resources in Daly City, Calif., 23 years ago, sewer cameras were in their infancy and most software could fit onto a double-density 3.5-inch floppy disk.


Now, in 2010, the city is keeping two steps ahead of clean-water regulations with an ambitious 10-year plan to scan, maintain and expand its sewer system. Crews use side-scanning camera technology, inspection reporting software, and GIS data systems.


With that setup, the department is embarking on its plan to scan, repair and rehabilitate the sewer lines under its jurisdiction. Capacity in some lines will also have to increase to reflect current usage.


The schedule includes 60,000 feet of inspection and repair per year for Daly City, plus 15,000 feet per year in other community systems for which Daly City is responsible. That schedule depends on the availability of staff and the TV truck, which is still used for inspecting new construction and previously scheduled pipe rehabilitation.


Birth by earthquake

Officially named the City of Daly City, this community of about 104,000 was founded in 1911 by citizens displaced by the San Francisco earthquake of 1906. The refugees settled on a ranch just south of Frisco on the Pacific Ocean. It was owned by John Daly, who subdivided his estate into housing tracts. Some of the city’s sewer lines date back to that time, and a second round of lines was built a half-century ago.


The city lies in San Mateo County, but the Water and Wastewater Department’s service area is geographically complex. It includes the North San Mateo County Sanitation District, a subsidiary of Daly City, covering the largest part of the community.


It also covers the city of South San Francisco, primarily the Westborough district, and unincorporated communities in San Mateo County, including the towns of Broadmoor and Colma. Wastewater from the area is treated and then released to the Pacific Ocean through a three-quarter-mile outfall pipe.


Donati started with the department as a mechanic’s helper and worked up to collection system field supervisor. “I had worked as a maintenance worker in a television truck back when they were still towing the camera through the lines,” he says. “When the Loma Prieta earthquake occurred in 1989, I was sent to Oakland with the tractor and a pan-and-tilt camera to search for survivors in the debris of the collapsed freeway.”


Master plan completed

A lot has changed since then. The city completed a sanitary sewer master plan in 2009, contracting with RMC Water and Environment to map the location and capacity of the lines. At the same time, the department was seeking a replacement sewer camera.


“The old one was a pan-and-tilt tractor model that was pushing eight or nine years old,” says Donati. “It was costing a lot of money to keep it going, and we were having trouble getting accurate marking locates with the locator.”


While some municipalities have adopted laser profiling, Donati says that technology would have limited use in Daly City’s system. “The lines are more than 90 percent vitreous clay pipe,” he says. “With clay, we don’t really need a reading on whether the pipe is true to size or experiencing deflection. And when laser profilers find cracks, it’s impossible to distinguish between a hairline and a severe crack.


“After 185 miles of laser profiling of clay pipe, you would query the system and get a list of cracks, but no indication as to the severity, or which lines require the most immediate attention.”


Side-scanning technology

The department instead chose to remodel the inside of the van and purchase a new camera unit: the DigiSewer camera with ROVVER crawler from Envirosight. The unit promises to capture side-scanning footage at up to 70 feet per minute. For Donati’s crew, that translates into about 7,500 actual feet per day.


The camera provides a conventional CCTV feed through one lens and 360-degree snapshots three seconds apart through a special fish-eye lens to provide sidewall scanning. Once the images are processed, operators can perform virtual pan-and-tilt maneuvers long after the scan has been completed.


“The camera can handle anything from 6-inch lines to 64 inches,” Donati says. “Offering us sidewall scanning and virtual pan-and-tilt along with CCTV combined the best of both technologies. Sometimes if we have protruding laterals or the flow is too high up in the line and we can’t do effective sidewall scanning, we switch to virtual pan-and-tilt. That even allows us to zero in on the lateral, look inside and zoom up.


The unit also offers inclination graphing and integrates fully with WinCan 8 pipe inspection survey reporting software, which logs digital video, still images and text data in an extensive, searchable database.


Using Pipeline Assessment and Certification Program (PACP) defect coding, WinCan allows operators to customize the scanning report, placing color markers on the scan image to highlight the locations of joints, service connections, cracks or any specific feature or defect recognized by the camera.


“Our department was one of the first in the state to adopt the use of computers in the early 1980s,” says Donati. “WinCan 8 is a nice addition to our software resources. The fact that software support was included with the purchase of the camera helped to seal the deal.”


Recording GIS data

As the televising van gathers information, the DigiSewer unit provides the software with GIS information, marking areas requiring immediate attention. Work crews drop underground service alert markers over the critical areas and send a message to home base, calling for immediate repair.


“The more you televise, the more issues you find,” says Donati. “It’s a balancing act. As a full-service unit, we have to balance scanning with the work that needs to be done.” The department uses in-house crews for all repairs, including pipe bursting on 8- to 12-inch lines. Many repairs are open-cut because the sewers lie close to the surface.


An atypical tough job handled fully by the in-house crews was the replacement of a 700-foot section of sewer along the city’s Parkview Avenue in 2009. “We were doubling the diameter of the line, but we had to deal with 34 utility crossings over the length of the pipe,” says Donati. “Much of the job was open-cut-and-replace — only one section was suitable for pipe bursting, because it had a small number of lateral connections. We handled it from start to finish, and I was really proud of the crew.”


Root problems are consistent with those of other municipalities. For San Mateo County, the culprits are redwood, eucalyptus, cypress and pine. “We have a rodder truck to deal with the roots, but if there’s damage, we perform repairs with Perma-Liner cured-in-place liner,” says Donati. The department has also contracted Duke’s Root Control to perform routine treatment with foaming herbicide.


Grease is an issue, as well. When workers spot a grease blockage, they clear the clog, and department personnel contact the business suspected of causing the problem. “It’s a source-control interceptor program,” says Donati. “We educate the source business on best management practices, then return in two to three months to see if there has been an improvement to the amount of grease coming through the service connection.”


The department is also in the middle of an extensive manhole rehabilitation program. “We pressure-wash the manholes, which are often corroded due to the effects of hydrogen sulfide,” says Donati. “We then use a rehab product from Epoxytec to give structural strength back to the manhole.”


Donati retired from the department in October, but the 10-year scan-and-repair plan continues. “We’ll miss Bob, but work continues,” says his former boss, collection and distribution manager Tom Piccolotti. “We’ll be looking back at a significant improvement to the sewer system from 2020.”


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