Bypass Pumps

Despite years of preventive maintenance and repairs, the Sacramento Area Sewer District (SASD) is currently addressing the deterioration of its Central Trunk, which serves the southeastern Sacramento Sewer System, using cured-in-place pipe (CIPP).

Constructed in the 1960s, the Central Trunk is a 15-mile stretch of pipeline delivering both residential and industrial sewage from mid-Sacramento County to the Sacramento Regional Wastewater Treatment Plant (SRWTP). An eight-mile stretch of the corroded reinforced concrete sewer pipeline will  be lined over a period of roughly 480 days.

In an effort to maintain access to area businesses and residences, the District is seeking to rehabilitate the pipeline using the dig-free method of cured-in-place pipe (CIPP). CIPP will be used to line sections that include 9,769 ft of 60-in. diameter reinforced concrete pipe, 9,273 ft of 54-in. diameter reinforced concrete pipe, 11,870 ft of 48-in. diameter reinforced concrete pipe, 10,753 ft of 42-in. diameter reinforced concrete pipe and 3,009 ft of 33-in. diameter reinforced concrete pipe. The relining contract was awarded to Insituform Technologies in May 2009.

During rehabilitation of the Central Trunk sewer pipeline, SASD is utilizing bypass pumping and sewer diversions to ensure uninterrupted use of the sewer system. Flow in the Central Trunk ranges up to 24 mgd. All Central Trunk rehabilitation work is occurring within designated manholes in the project area.

To line using CIPP, all flows must be diverted or bypassed. Temporary diversion of sewer flow is required around and through both public and private property, including under Highway 99. Insituform Technologies called on bypass pumping specialists Godwin Pumps to assist in the diversion of flow through multiple sideline bypasses, ranging from 6 to 15 in. in diameter.

Whether working around a manhole or implementing bypass pumping, rehabilitation will result in noise implications for some adjacent properties. However, SASD is working to reduce these impacts through implementation of several mitigation measures outlined in the project’s Noise Reduction Plan. This includes placement of temporary noise walls/barriers, moving equipment away from homes and schools, use of quieter equipment and restrictions on use of equipment.

Godwin Pumps provided its Critically Silenced units to meet these requirements. The Godwin sound-attenuated units minimize and reduce sound generated by diesel-driven pumps, often to as low as 63 dBA at 30 ft. Designed for applications where noise levels are a priority, the units feature special enclosures engineered to keep operating noise to a minimum. Godwin’s Critically Silenced and Quiet Vandal-Pac units also include critical grade silenced mufflers and silenced priming exhausts to further reduce noise levels.

“SASD required the use of noise-reducing equipment as part of its plan,” said Godwin Pumps western regional manager Ron Askin. “We worked with Insituform to provide them with our Critically Silenced units. These units are enclosed in galvanized steel with noise-deadening insulation. In addition, they feature hospital grade, silenced mufflers. To give you some perspective, the diesel engine on this unit sounds like little more than your typical car running outside your door. The decision to use this equipment should help minimize disruption to residents.”

Beginning with the 8.1-mgd (5,625-gpm) Gerber Road Bypass, Godwin placed four of its Critically Silenced 8-in. CD225M diesel Dri-Prime pumps, two of its 6-in. CD150M diesel Dri-Prime pumps and two runs of 18-in. HDPE temporary pipelines measuring 5,750 ft long each along several high-traffic, four-lane roads.

In another bypass segment, Godwin established a Heidra hydraulic submersible pump pit bypass. In this bypass, Godwin assembled five Critically Silenced 12-in., Heidra HS300 diesel powerpacks and five Heidra HS300 pump-ends.

This bypass segment relied on three 18-in. HDPE discharge lines, each measuring 7,800 ft in length. In addition, two Critically Silenced 6-in. CD150M diesel Dri-Prime pumps served as an 18-in. sideline and two additional 4-in. Critically Silenced CD103M diesel Dri-Prime pumps served as a 10-in. sideline.

Godwin connected the three 18-in. lines into a single discharge at a 108-in. interceptor. This bypass will allow the flow along Mack Road to be surcharged from Franklin Boulevard to Stockton, Elsie and Mack Road.

Five 12-in., Critically Silenced DPC300 diesel Dri-Prime pumps discharge into three 18-in. HDPE lines running 3,550 ft. These pumps will distribute the 13.4 mgd (9,380 gpm) through the three discharge lines.

SASD has communicated early and often with area residents and businesses to inform them of why the work needs to be done and potential impacts to the community. SASD uses newsletters, Web site updates, e-mails, FAQ sheets, Twitter and Facebook updates and public open houses to convey its message.

During construction, a seasoned construction inspector from the County Construction Management Division has been assigned as project liaison. The project liaison makes personal contact with impacted residents and businesses approximately one week in advance of construction activity in their neighborhood.

By keeping the public up-to-date on construction activities through various media and personal contact, there have been minimal complaints and no project delays.

“This project is truly a model that needs to be replicated,” said Godwin Pumps Mira Loma branch manager Russ Pavur. “SASD has done its homework on the Central Trunk and has plotted out a well-thought plan for rehabilitation.”

Stephanie E. Hassler is corporate communications manager for Godwin Pumps.