San Francisco Public Utilities Commission
San Francisco, California
Starting in the 1990s, we have provided a variety of sewer cleaning services across the city involving debris and sediment removal from virtually every kind of sewer – from egg-shaped to circular, horseshoe-shaped, and box sewers.
Work included cleaning and removing sludge, silt, and debris utilizing PPSI’s proprietary hydro-jetting methods for approximately 18,000 LF of sewer ranging from 84’’-210’’ in diameter. PPSI successfully removed 2,430 CY of material, and finished the project 10 months ahead of schedule.
The most difficult challenge in this project was cleaning the Channel Pump Station Box Sewer, which was 17.5’ wide and 40’ deep. This particular box sewer conveys 2/3 of all wastewater in the City of San Francisco to the South East Wastewater Treatment Plant. This box sewer cannot be taken offline, it cannot be diverted, and must operate at the maximum carrying capacity possible. The waste water conveyance system in the City of San Francisco is a combined storm and sewer system. There are varying degrees of debris accumulation and very high levels of flow. Consistent cleaning is required to maintain this system so that the waste water collection system can accommodate sewer flow as well as all major storm events.
Offset manholes gave PPSI access to the Box Sewer. At each access structure, PPSI was required to implement a system of rigging, pulleys, electric hoists, and winches in order to effectively mobilize our sewer cleaning equipment into the center of the box sewer. This rigging system was installed and remained within the sewer until all cleaning was completed.
PPSI built a custom jetter nozzle designed to produce a 30’ wide spray pattern at just 10 feet away from the nozzle head. In addition to using a custom nozzle PPSI mobilized 2 ea of its proprietary grit extraction pumps into the sewer so as to maximize our production and efficiency of grit removal. Working 24 hours a day was not allowed in this location as the Channel Box Sewer is located adjacent to the AT&T Baseball Stadium and highend residential condos. The width of the box sewer allowed us to mobilize two pumps and as a result, PPSI was able to consistently remove 45 cy of material from the sewer within a single shift. Approximately 1,000 CY of material was removed from the box sewer in just 22 ea 12 hour shifts.
A large portion of the work required in this project was conducted in the heart of the financial district of San Franisco. PPSI’s traffic control and cleaning plans had to accomodate several conditions such as San Francisco Municipal Transportation Authority bus routes, cable car routes, electrical overhead contact transit wires, as well as very dense pedestrian traffic.
By modifying our jetting and pumping technology we were able to effectively clean the Channel Box Sewer while also adhering to strict work hour restrictions. PPSI was given a total of 24 months to complete the work required in the SFPUC project.