Name: |
City of Torrance Stormwater Basin and Treatment Wetlands Enhancement |
Company: |
City of Torrance |
Project Location: |
The project is located at three stormwater basins in the City of Torrance (City). The Amie Basin is located north of the intersection of Amie Avenue and Spencer Street. The Henrietta Basin is located west of the intersection of Spencer Avenue and Henrietta Street. The Entradero Basin is located at Entradero Park, which is northwest of the intersection of Del Amo Boulevard and Anza Avenue. |
Project Photo: |
|
Project Description: |
On July 15, 2003, the Los Angeles Regional Water Quality Control Board (LARWQCB) established the Santa Monica Bay Beaches Bacteria Total Maximum Daily Load (SMBBB TMDL). This TMDL requires cities to improve water quality along the shoreline of the Santa Monica Bay to meet dry- and wet-weather targets for bacteria. The City makes up 57 percent of the 2,745-acre drainage area tributary to Herondo Drain. The Stormwater Basin and Treatment Wetlands Enhancement project was developed to reduce bacteria levels in the Herondo Drain by improving water quality in the City’s three stormwater basins: the Amie, Henrietta, and Entradero Basins. Two treatment wetlands and two infiltration basins were designed to infiltrate, retain, and treat runoff, addressing the various TMDLs in the Santa Monica Bay. Infiltration contributes to recharging the local groundwater aquifers. The infiltration basins and wetlands also provide flood control benefits through increased stormwater storage. The project enhances wildlife habitat and recreational areas through the use of treatment wetlands, public education, walking trails, and signage. Over 180 automatic retractable screens were also installed at curb inlets, which allow water to enter catch basins while trapping debris at the curb. |
Project Justification: |
California is experiencing one of the most severe droughts on record. The demand for innovative, multiuse projects that incorporate water conservation while improving water quality is imperative. Meanwhile, cities are under increased pressure from stakeholders with competing interests to provide open space, recreational facilities, and responsible environmental stewardship. The City of Torrance embraced this challenge by embarking on this transformative capital improvement project which, because of its original and effective approach, was able to procure $3.3 million of Proposition 84 grant funding from the Santa Monica Bay Restoration Commission. The US Bureau of Reclamation also granted funds because the project included use of recycled water, which reduced potable water use.
The Stormwater Basin and Treatment Wetlands Enhancement project exemplifies a bold, multi-faceted approach to challenges facing many cities in California. Planning capital improvement projects with a process that addresses the dire need for groundwater recharge and stormwater use, while improving water quality by enhancing and increasing the use of existing infrastructure, is a unique, cost-effective, multi-pronged solution that benefits the community. One of the unique construction elements involved removing impervious materials and replacing those areas with treatment wetlands. The wetlands utilized ponding and water depth zones to promote native habitat growth.
The project also included the creation of additional walking trails to provide increased recreational opportunities to the community. These improvements incorporate educational components with the addition of an outdoor classroom space and Best Management Practice (BMP) explanation signage. These features are helping to increase public awareness of BMP importance and functions in the surrounding community. The added environmental consideration of protecting and expanding the native habitat by creating dual-purpose wetlands that also treat runoff is an exemplary, responsible approach that demonstrates how compliance challenges can present opportunities to affect change.
Wetlands are among the most effective stormwater practices in terms of pollutant removal and provide aesthetic appeal while enhancing the habitat. The constructed wetlands treat stormwater using several consecutive shallow and emergent zones, which increase the flow path. The grade changes, along with carefully selected vegetation, treat the urban runoff that enters the facility. When the storage capacity is exceeded, the discharged flows are still partially treated through several mechanisms. The wetland vegetation reduces the velocities of storm flows allowing particles to settle, which addresses sediments and sediment-bound contaminants, such as phosphorus and trace metals. The plants provide filtration and physically remove pollutants as water flows through the system. The plants also contribute to pollutant removal, as the organic matter acts as long-term storage for several pollutants. The infiltration basins and wetlands provide flood control benefits through increased stormwater storage.
In addition to the project achieving its intended goal of addressing the TMDL, stormwater is used at the basins for irrigation. Stormwater reduces the potable water demand by approximately 2,800,000 gallons annually. Sustainability improvements included slope stabilization, habitat creation and restoration to accommodate burrowing owls and legless lizards, and native planting for purification of toxic elements in water. The increased vegetation reduces the City’s carbon footprint and increases the sustainability of the system. The design provides sustainable stormwater quality mitigation education for students and neighborhood communities by building an Americans with Disabilities Act (ADA) accessible walkway to the outdoor classroom gathering space, an island, and two viewing areas with interpretive signage, seating, and shaded areas.
|
Special Circumstances: |
Special Relationships Generated: The Stormwater Basin and Treatment Wetlands Enhancement project has bolstered the relationships within the local community by encouraging community involvement and awareness and providing educational opportunities for children, students, and other community members. The walking trails invite visitors to stroll with family and friends as they share quality time together observing wildlife and increasing understanding. Longtime Torrance resident, Alexis Alipuria, praised the project, saying, “[The project] has taken an empty, dead space and made it purposeful and beautiful.”
Obstacles Overcome: Working in natural environments can present a number of challenges relating to native plants and wildlife. The Stormwater Basin and Treatment Wetlands Enhancement project involved conditions under which sensitivity to accommodate the natural environment was critical. The legless lizard, which is listed by the State of California as a species of special concern, dwells underground in environments similar to the stormwater basin construction sites. To protect the species from harm, several pre-construction surveys were performed, and continual monitoring was carried out as construction progressed. To avoid impacts to nesting birds, surveys were conducted to ensure nesting was complete prior to construction commencement and continued to be performed throughout the construction process to prevent any potential disruptions. In addition, the basins were re-designed to accommodate burrowing owls and create additional habitat. Clearing and grubbing methods were altered to preserve native plant habitat during construction. Through taking these precautions, the City of Torrance successfully minimized negative impacts to these sensitive areas, and the project will provide enhanced plant and animal habitat for years to come.
Accolades Received: This project has been honored with several prestigious awards, including the 2015 American Public Works Association (APWA) Project of the Year Award for Water Quality, 2015 California Stormwater Quality Association (CASQA) Outstanding Stormwater BMP Implementation Project Award, and 2014 Storm Water Solutions Top Stormwater and Erosion Control Project Award. The project has also been highlighted in several articles and presentations, as cited below.
Dettle, John. ”City of Torrance: Multibenefit Approach to Improving Water Quality,” 2014 CASQA Conference, Garden Grove, CA. 17 September 2014.
“2014 Top Storm Water and Erosion Control Projects.” Stormwater Solutions. MediaPress Studios, Web. 02 June 2015.
Meyers, Lee. ”What a Small Park in Torrance can Teach Rest of L.A.,” Heal the Bay Blog. Heal the Bay,
05 December 2014. Web. 29 May 2015.
”City of Torrance: Stormwater Program Highlights.” South Bay Stormwater Program. WordPress,
28 September 2011. Web. 29 May 2015.
http://www.torranceca.gov/16160.htm
|
Project Attachments: |
See attachment entitled “Torrance Layout Renderings.” |
Award Citation: |
The Torrance Stormwater Basin and Treatment Wetlands Enhancement involved the design of two treatment wetlands and two infiltration basins to retain, treat, and infiltrate stormwater runoff. The project is a bold approach to stormwater management challenges facing many California cities. Walking trails and public space provides increased recreational opportunities for the community, while an outdoor classroom setting and signage facilitate sustainable stormwater quality mitigation education. |
Suggested Award Summary: |
The Torrance Stormwater Basin and Treatment Wetlands Enhancement project involved the design of two treatment wetlands and two infiltration basins to retain, treat, and infiltrate stormwater runoff. The project exemplifies a bold, multi-faceted approach to challenges currently facing many cities in California and contributes to important advancements in stormwater management and construction. Addressing the dire need for groundwater recharge and stormwater use, while improving water quality by enhancing and increasing the use of existing infrastructure, is a cost-effective, multi-pronged solution that benefits the community. The estimated annual pollutant load reduction for this project is 91 percent, and using stormwater for irrigation reduces the potable water demand by approximately 2,800,000 gallons annually.
The project included the creation of additional walking trails, which provide increased recreational opportunities for the local community. In addition, the trails incorporate educational components, such as an outdoor classroom space with BMP informational signage. These features are helping to create a behavioral shift in Torrance and neighboring communities by increasing public awareness of BMP importance and functions.
This project also involved sustainability improvements, including slope stabilization, habitat creation and restoration to accommodate burrowing owls and legless lizards, and native planting for purification of toxic elements in the water. The added environmental consideration of protecting and expanding the native habitat by creating dual-purpose wetlands that also treat runoff is an exemplary, responsible approach that is a bellwether of how compliance challenges can present opportunities to affect change.
|