Dec 07, 2020

Underground System Diverts Storm Water

This is Storm Water Solutions 2020 Top Project. 


Location: Carson, California

Cost: $18.72 million

Size: 13.54 acre-foot system

Owner: City of Carson, California

Designer: Tetra Tech

Contractor: OHL USA

Manufacturers: StormTrap, Jensen, KSB, Pratt 

A large underground system was installed at the Carriage Crest Park as part of a storm water management project in Carson, California. The aim of this $18.72 million project was to divert millions of gallons of storm water each year to help the city and unincorporated areas of Los Angeles County. As a result, this would protect waterways, meet MS4 permit requirements and increase water supply to the local wastewater treatment plant

The project was a collaboration between the city of Carson, county of Los Angeles, and the Sanitation Districts of Los Angeles County.

Carriage Crest Park is situated next to two large storm drains with a total drainage area of 1,146 acres. The site is across the street from the Joint Water Pollution Control Plant (JWPCP), the Sanitation Districts’ largest wastewater treatment plant. 

A major challenge for the project was the quality of the soil. A soil study conducted at the site revealed the presence of DDT in the top 2 to 3 feet of the soil, as well as pockets of varying depths. Since the contaminated soil could not be reused on-site, the soil required transport to a specific disposal facility. There was also a concerted effort to lease a nearby property in order to stockpile clean soil.

“These issues were addressed and corrected immediately by StormTrap staff,” said Julio Gonzalez, sustainability administrator for the city of Carson about the gaps. 

To account for the system’s magnitude, the installation occurred in phases, permitting travel over the basin throughout construction. 

About the author

Winner profiles were compiled by SWS Managing Editor Katie Johns and Associate Editor Cristina Tuser. Johns can be reached at [email protected] and Tuser can be reached at [email protected]