Water quality project begins in Ashley Falls neighborhood

Construction has begun on a new water quality project on Pearlman Way and Carmel Knolls.
(Karen Billing)

A city of San Diego water quality project has begun work in the Ashley Falls neighborhood of Carmel Valley.

The construction of the large-scale storm water storage and treatment system prompted some “chaos in the neighborhood” as residents weren’t exactly sure what was happening with sudden street closures, vegetation removal and numerous construction trucks filling the corner of Carmel Knolls and Pearlman Way.

Resident Matt Modugno said while a sign announced what the project was, many still had questions about the purpose of the project and why there were never any renderings released to the public about what was going into the middle of their neighborhood.

“This simple gesture would have appeased many residents and answered many questions,” Modugno said.

The project, which has been in the design stage for four years, includes the construction of three reinforced concrete storm drain pipes for low-flow collection and a shallow biofiltration basin.

“The purpose of the project is to improve water quality in storm water runoff for the area, which discharges to Carmel Valley Creek, Los Penasquitos Creek, Los Penasquitos Lagoon and the ocean,” said Alec Phillipp, senior public information officer for City of San Diego’s public works department.

The project will help reduce pollutants such as bacteria, metals and nutrients in order to protect the Los Peñasquitos Creek subwatershed.

The project is listed as a priority in the Los Penasquitos Water Quality Improvement Plan that was developed by the City of San Diego in collaboration with interested stakeholders and submitted to the Regional Water Quality Control Board. The plan demonstrates how the city will meet federal Clean Water Act regulations and the Municipal Storm Water Permit requirements.

Some residents questioned whether there could have been an alternative placement for the pipes, such as in an undeveloped area, rather than in the middle of a residential neighborhood.

“This location was selected as it provides a great opportunity to intercept storm water runoff from existing storm drain systems within a developed area and discharge low flows into an above ground storm water basin,” Phillipp said.

The storm water basin allows natural treatment mechanisms using vegetation and soil amendments to help filter runoff before conveying the treated flows back into the storm drain system.

“Other locations within the watershed were evaluated and found infeasible,” Phillipp said. “There are very limited opportunities within the downstream portion of the sub-watershed for a large scale project on public land. There are only six other locations identified within the Carmel Creek sub-watershed for water quality projects that collectively would help reduce pollutants to meet storm water regulatory requirements.”

A rendering of the proposed project.

The project was initially approved by the Carmel Valley Community Planning Board back in 2015, before the city underwent the four-year design process. The site was originally planned to be fenced-in but the planning board encouraged the city to include more passive park elements such as landscaping and maintaining public access with decomposed granite walking trails. The city agreed to include elements that improve the aesthetics and provide benefits for the community—in addition to the walking trail with a footbridge, there will also be interpretive signage.

While neighbors have complained that the city seems to be “stripping” the land of vegetation, according to Phillipp, there will be minimal impacts to existing trees. Phillipp said the 18 existing trees on the property will be protected in place or relocated. The city also plans to plant 22 new Lemonade Berry shrubs/small trees in addition to vegetation that will be planted throughout the project area.

Construction on the $650,000 project is expected to be completed by May 2020.