Rainbow CPG hears presentation on nutrient reduction and street improvement project

San Diego County’s Department of Public Works is planning a project whose primary purpose will be to reduce nutrient discharge into Rainbow Creek and which will also provide improvements to some Rainbow roads. The Rainbow Community Planning Group learned about the project, Nov. 18.

The presentation was a nonvoting item although, after the design is complete, DPW will return to the planning group for a formal recommendation. The presentation was provided by Amanda Parra, who is a project manager in DPW’s Capital Improvement Program Division.

“It’s very important for our community,” Paul Georgantas, planning group chair, said.

The goal is to reduce total maximum daily load contaminant levels in Rainbow Creek.

“Both nitrogen and phosphorus go in,” Parra said.

In 2006, the Regional Water Quality Control Board established maximum levels for Rainbow Creek.

“That’s going to be the key factor that drives the extension improvement and the county's involvement,” Parra said.

The county has been determining the best way to reduce nutrients. The county is also trying to determine how to fund the project.

“The county has pursued various grant applications,” Parra said.

The RWQCB issued a municipal separate storm sewer system permit to the county in 2013 which has an enforceable TMDL reduction for Rainbow Creek. The deadline for final compliance with those maximum load levels is Dec. 31, 2021.

“The county is looking toward improving a handful of elements to reduce that nutrient level,” Parra said.

The county’s capital improvement project will use subsurface wetlands channels. Adjacent road runoff will be conveyed through those channels which will deliver the water – minus whatever was used for the vegetation or soil – to collection pipes and then to the discharge system at Rainbow Creek.

The capital improvements would take place along Huffstatler Street by Second Street, Huffstatler Street south of Fifth Street, Fifth Street between Huffstatler Street and Rainbow Valley Boulevard, Rainbow Valley Boulevard from Chica Road to Rainbow Creek Road, and the northern part of Rainbow Valley Boulevard.

Some modifications to driveways will be necessary near Fifth Street and Huffstatler Street.

“We’re looking at making 18 driveway improvements,” Parra said.

The driveway work will also address culverts underneath a driveway.

“We’ll be looking at replacing those culverts,” Parra said.

The work will also include replacing other drainage channels to convey adjacent road runoff. Driveway and culvert improvements will also be made for the Rainbow Valley Boulevard segment between Chica Road and Rainbow Creek Road, and seven driveways will be modified for the 800-foot northern Rainbow Valley Boulevard segment.

Pedestrian improvements will be made at the intersection of Huffstatler Street and Fifth Street. Ramps meeting Americans with Disabilities Act standards will be added on both the east side and the west side of Huffstatler Street.

“We also found some opportunities to do some traffic improvements to the intersection of Chica Road and Rainbow Valley Boulevard,” Parra said.

Those traffic improvements will involve widening some segments and turn radius modification.

The planned improvements to the north side of Fifth Street include an 8-foot-wide shoulder. On the south side, the installation of a decomposed granite pathway will avoid impacts to an existing facility while enhancing pedestrian safety near Rainbow Park and Vallecitos Elementary School.

“We figured we’d take the opportunity,” Parra said.

A sidewalk – 4 feet wide by the park and school – will be the only paved pathway if plans do not change.

“Sidewalks are not proposed,” Parra said.

The sidewalk by the school will meet ADA standards and will also have curb ramps meeting ADA standards. The sidewalk will be on the south side only while drainage will be implemented on the north side of Fifth Street.

About 535 feet of sidewalk will be installed along with curbs and gutters.

“That was the only area we identified because of the close proximity to the school and the park,” Parra said.

In addition to filtering runoff the channels will increase the water volume capacity.

“You may see a reduction in the flooding,” Parra said.

The volume will be increased through increasing the depth of the channels.

“We should not be including any type of structures that would negatively impact the flooding conditions in this area,” Parra said.

The current cost estimate for the project is $11.4 million, including $7.5 million for construction expenses.

“We’ll be doing quite a bit of over excavation, bringing in suitable material,” Parra said.

The work will also include lining, geotechnical studies and groundwater testing.

The design phase is expected to be complete in spring 2021, and Parra or another DPW representative will return to the planning group with the refined project. The planning group will be asked to make a recommendation on that version of the improvements.

DPW will also develop an environmental document, which is expected to be a Mitigated Negative Declaration.

“We are looking to mitigate any impacts that are significant,” Parra said.

A draft MND will be released for public review, and comments by various state and federal permitting agencies as well as by local agencies or citizens may create modifications. The environmental phase will also determine what permits are necessary, although those do not need to be obtained before the certification of the MND.

“It may require some additional permitting from the U.S. Army Corps (of Engineers),” Parra said.

The RWQCB may also require permits.

DPW has targeted the June 9, 2021, county Board of Supervisors meeting for the authorization to solicit bids and subsequently award a construction contract.

The bids will be reviewed after the submission deadline and the contract will be awarded to the lowest responsible bidder. Work is expected to begin in late summer 2021 and take approximately one year to complete.

DPW will maintain the road and channel facilities, which will be inspected one to two times a month.

“This is arguably the biggest project we've had in Rainbow in a long time,” Georgantas said. “I think it’s really great for our community.”

Joe Naiman can be reached by email at [email protected].