Rainbow MWD awards North River Road Land Outfall rehabilitation contract

The Rainbow Municipal Water District will be rehabilitating its North River Road Land Outfall pipeline, and Hoch Consulting will be preparing the bidding documents and providing engineering support to the Rainbow district.

A 5-0 Rainbow board vote, June 23, approved a $151,180 contract with Hoch Consulting, which is headquartered in San Diego. The contract does not have a specific end period, although construction is anticipated to begin in early 2021 and take approximately eight weeks.

“It’s an important project to maintain a critical part of our wastewater infrastructure,” Tom Kennedy, Rainbow general manager, said.

The North River Road Land Outfall conveys wastewater to Oceanside’s San Luis Rey Water Reclamation Facility. The pipeline is nearly 3 miles in length, from just west of state Route 76 to the intersection of Stallion Drive, and 58 manholes provide access to various parts of the infrastructure.

The vitrified clay pipe is 15 inches in diameter, and the sewer relies on gravity for its flow.

The rainfall during weather year 2018-2019 caused wastewater flows at the Stallion Drive and North River Road flow metering stations to exceed capacities. The increased flow is believed to be due to significant infiltration and intrusion of rainwater into the wastewater collection system.

In June 2019, Rainbow staff began an evaluation of the vitrified clay pipe which involved clearing the line and then conducting a video and photographic inspection of nearly 1 mile of pipeline and 15 manholes. The video inspection revealed multiple repair needs. Another section was inspected in October 2019.

Rainbow staff began developing the logistics of repair efforts. The plans and specifications would be addressing broken or badly cracked sections of pipe, infiltration and intrusion, raising manholes to finish grade, lining existing manholes and providing cast in place pipe at the worst sections.

“The pipeline’s almost 50 years old,” Kennedy said. “It needs attention.”

The March 2020 rains caused another overflow of the pipeline. Rainbow staff conducted video and photographic inspections and observed two sections which are in imminent danger of collapsing.

Kennedy declared an emergency April 17, so that repair work could commence before the next Rainbow board meeting. The April 28 board vote ratified Kennedy’s action and appropriated additional funding for the repair work.

Kennedy issued a contract to SCW Contracting Corporation, which is based in the town of Rainbow, and SCW began the repair work, April 19.

Rainbow had planned to repair the North River Road Land Outfall over a multiyear period, but the immediate risk led to the decision to repair the entire three-mile pipeline as soon as possible.

During the emergency Hoch Consulting was retained to assist Rainbow staff in finalizing the plans and specifications. As the inspections and research were being conducted, Rainbow staff decided that Hoch was best suited to expand and expedite the plans and specifications needed for the repair work to be advertised for bid.

Rainbow staff and Hoch worked together to prepare a phased construction approach which will allow the sections with the worst conditions to be addressed first and remaining phases to follow.

“They’re going to be doing the design,” Kennedy said.

The first phase will excavate and make repairs to the pipeline, replacing the vitrified clay pipe with polyvinyl chloride pipe. The second phase will line high-priority sections with cast in place pipes. The third phase will rehabilitate manholes.

“It will be a couple of miles that we’ll be relining,” Kennedy said. “It will be short segments that will be replaced. The full line will be relined.”

Access issues, both for repair crews and for motorists along North River Road, led to the decision to reline rather than to replace the majority of the pipeline.

“It’s a very small road and there’s a lot of traffic on it,” Kennedy said. “The pipeline’s also very deep.”

The minimized traffic control and excavation measures will also allow for a shorter construction period.

“We want to get all the work done hopefully in under a year,” Kennedy said.