2017 CASQA Award Winner - Outstanding Ultra-Urban Sustainable Stormwater Project: Broadway Neighborhood Stormwater Greenway Project
Like much of the City of Los Angeles, the Broadway neighborhood of South Los Angeles is densely developed, with little-to-no space available for the implementation of multi-benefit stormwater control measures (SCMs). This area includes dense clusters of commercial, industrial, and residential developments. Runoff from the neighborhood discharges to the Los Angeles River, listed as an impaired waterbody for pH, metals, coliform bacteria, trash, pesticides, nutrients, and oil and grease. Local water supply initiatives encourage development of supplies derived from stormwater, among other sources; and, as with many highly-urbanized areas, flooding of stormwater facilities poses risks during significant storm events.
Within this neighborhood, the City of Los Angeles Bureau of Sanitation (LASAN) recently completed the Broadway Neighborhood Stormwater Greenway Project (Project), a regional stormwater and dry-weather runoff capture project developed to help improve downstream water quality, reduce neighborhood flood risk, and increase groundwater supplies through the deployment of Low Impact Development (LID) and SCMs. The Project was identified as an ideal local project for implementation of neighborhood-wide LID designs through the Water Replenishment District (WRD) of Southern California’s Central and West Coast Basins Distributed and Regional Stormwater Capture Feasibility Study.
The Project includes four levels of stormwater capture and infiltration SCMs: (1) residential rain gardens for treatment of up to eight acres; (2) neighborhood-scale LID in the form of street-end infiltration catch basins for treatment of up to 12 acres; (3) commercial LID measures for treatment of runoff from three acres; and (4) a sub-regional-scale, 417,000-gallon infiltration gallery for treatment of runoff from 30 acres of mixed land uses during wet weather design storm events and up to 220 acres during dry-weather and smaller storm events. Collectively, the SCMs/LID measures have been constructed to systematically capture, treat and infiltrate stormwater runoff; augment groundwater recharge; reduce risk of flooding; and help address Los Angeles River Total Maximum Daily Load (TMDL) water quality requirements.
Following completion of the Project’s construction in April 2016, monitoring was initiated to assess the effectiveness of the Project. During the monitoring period, 96 percent of the equivalent runoff from the Project design area was captured and infiltrated. Additional volume from the upstream tributary area was also captured and infiltrated over the course of the monitoring period, increasing the equivalent capture efficiency to well-beyond 100 percent of the design capture efficiency. Other notable Project benefits include:
- An estimated long-term average annual infiltration volume of 41 acre-ft;
- The implementation of a successful public outreach and education program, which included direct mailers to residents in the Project neighborhood; stakeholder engagement, including a partnership with a local church; a community meeting in coordination with the local City Council member; a Project website; and an outreach phone number;
- Conservation of local water supplies via the replacement of turf and installation of drought-tolerant rain gardens, native landscaping, and mulch; and
- Open space benefits and pedestrian friendly green connections within the community throughout the residential neighborhoods and the commercial district
Overall, the Project, which was funded in part from the State of California Water Resources Control Board (SWRCB) Proposition 84, was implemented via a successful partnership between LASAN, the City of Los Angeles Bureau of Engineering, the Los Angeles Department of Water and Power, the SWRCB, WRD, Council for Watershed Health, Santa Monica Bay Restoration Commission, and Geosyntec Consultants.
Dr. Mark Hanna is a California registered professional engineer and a senior principal managing Geosyntec Consultants’ Downtown Los Angeles office. Mark specializes in large system hydraulics, hydrology, surface water and groundwater management, and ecosystem restoration. He provides civil engineering and managerial oversight for multi-sector clients including governmental agencies, private developers, and non-profit organizations alike. His 20 plus years of experience in water resources and integrated planning allows him to offer multi-sector clients comprehensive water resource solutions in the natural and urban environment.