View Downloadable PDF Version

Introduction

Northern California is home to some of California’s most admired landscapes, such as Yosemite and the Redwood Forest, but the Silicon Valley also serves as a global center for technology and innovation. San Jose is the largest city in Silicon Valley and third-largest in California, with a population of over 1 million and covers around 180 square miles.

Nestled along San Francisco Bay’s southern shoreline, San Jose stormwater runoff impacts six local watersheds. To protect these watersheds, the City of San Jose is pursuing a multi-phased project to implement large-scale stormwater solutions across the city in three of the largest watersheds: Coyote, Guadalupe, and San Tomas.

Goals

The City of San Jose’s overarching objective is protecting local watersheds, but a city of this size produces many contaminants and byproducts from heavy vehicle and foot traffic. Pollutants of concern consist of: trash, debris, plastics, hydrocarbons, and sediments.
The goal for this large-scale full capture project is handling the challenging high-flow rate demands of a 10-year storm and meeting the California State Water Resource Control Board (CASWRCB) Full Trash Capture High Flow requirements. In previous phases, the City of San Jose used manhole-based hydrodynamic separators with external bypass structures. Because of their inherent depth, these solutions proved costly in both maintenance and installation challenges around dewatering* costs.
*Dewatering: the removal of groundwater or surface water during construction.

Solution

The City of San Jose chose five of Bio Clean’s 11×17, DSBB Separators (Debris Separating Baffle Box) and one 11×25, for locations throughout the city. Bio Clean’s in-house engineering team designed the DSBB Separator units with height in mind; the DSBB requires less depth than manhole hydrodynamic separators, resulting in lower dewatering costs during installation and easing future maintenance. All six DSBB Separators are individual precast concrete vaults with internal bypass for high flows, eliminating additional junction boxes and diversion structures while still designed for a 10-year storm of over 200 cfs!

The DSBB Separator is a proven, approved hydrodynamic separator that can manage high volumes of site runoff and stormwater’s toughest pollutant loads, including trash, debris, hydrocarbons, and sediments. This high-flow device certified by the CASWRCB for Full Trash Capture is designed to isolate and store trash, debris, and organics in a dry state suspended above any water below. This feature makes it easier for maintenance crews to clean, and prevents nutrient leaching, bacterial growth, and bad odors. In addition, the DSBB Separator doesn’t require man entry, keeping service intervals safe and saving the city on long-term maintenance costs and liability.

Conclusion

This Full Capture stormwater project in San Jose goes beyond meeting local regulations and separating trash, debris, hydrocarbons, and sediment from stormwater throughout a large city. The DSBB Separators’ ease of maintenance and CASWRCB Certification allows each system to operate efficiently at a reduced cost, and ultimately helps the City of San Jose sustainably reach their goal of protecting vital watersheds for years to come.

REFERENCES
1. Google Maps Website