Rainbow MWD approves wastewater outfall replacement contract

The Rainbow Municipal Water District approved a professional services contract with Tetra Tech to design the replacement of the district’s wastewater outfall facility.

The 4-0 board vote Oct. 23, with Jack Griffiths abstaining, approves a contract with Tetra Tech for an amount not to exceed $198,300. Seven firms responded to the district’s request for proposals, and district staff reviewed and ranked the proposals before recommending that Tetra Tech was the most qualified firm.

The total design and permitting cost for the project is estimated at $1 million while the district estimates a construction cost of $6 million should the design phase confirm the need for a replacement. The replacement would expand the size of approximately three miles of the district’s outfall sewer line on North River Road to the Stallion Flow Meter Station. The existing 15-inch gravity sewer between Lift Station 2 and the Stallion Flow Meter Station would be upgraded to a 21-inch diameter pipeline while the 12-inch cast iron force main between Lift Station 2 and the outfall would be replaced with 14-inch and 18-inch plastic pipeline.

“The current sewer line flowing from our treatment plant to Oceanside is undersized,” said Rainbow general manager Dave Seymour.

The district’s 2006 wastewater master plan states that the pipelines on North River Road are undersized both for existing peak wet weather flow and for ultimate peak dry weather flow.

“Just by visual observation we know that the line is flowing above capacity,” Seymour said. “We want to verify that.”

The pipeline itself was constructed in 1972, and closed circuit television reports indicate that the existing pipe is cracking at several locations and has developed sags.

Tetra Tech’s July 30 proposal committed Mark Bush, who is currently working with the Rainbow district on the Highway 76 East Segment Realignment Project, as the project engineer for the outfall replacement. Tetra Tech’s projects also include a parallel waterline to the outfall along North River Road for the City of Oceanside, and the firm has been a subcontractor consultant for Rainbow’s North, Northside, and Morro reservoir rehabilitation projects.

Tetra Tech’s proposal calls for meetings, site visits, and research prior to the design phase itself, and Tetra Tech will also provide opinions of probable construction cost. The information will also allow Rainbow staff to determine whether a new line is actually needed.

“This project will provide all of that in the analysis,” Seymour said. “Ultimately we should end up with a set of blueprints.”