Location: 

Unincorporated Pasadena Community Area

City or County Responsible for Project: 

Los Angeles County Department of Public Works

Award Category: 

Narrative Description Of Your Entry: 

Brandon Street and Green Street Road Project: An Investment in Sustainability Brandon Street and Green Street Road Project is an urban residential roadway improvement project by the Los Angeles Department of Public Works which incorporated a variety of sustainable low impact development (LID) features for roadway design and storm-water management and treatment. The approximately $2 million project improved a three-quarter mile stretch of roadway on Brandon and Green Streets in the unincorporated area of East Pasadena. Brandon Street and Green Street Project was originally conceived as a traditional road improvement project with a new storm drain component in an urban residential neighborhood. The project scope included construction of missing roadway, sidewalk, and curb improvements to match the surrounding neighborhood street improvements. Residents that lived within the project limits had been requesting construction of the missing improvements in front of their properties for many years and funding had now been identified to proceed. A traditional underground storm drain lateral was also proposed for drainage for the new roadway. The Project was re-designed to feature sustainable design methodologies that enhance community aesthetics, improve pedestrian safety, and provide sustainable storm-water management through infiltration features. The LID features include construction of parkways with bio-retention planters, narrowed traffic roadways, larger curb returns with ADA compliant curb ramps, porous concrete gutters and porous sidewalks, permeable pavers at crosswalk locations, and an underground storm-water infiltration basin to capture the hydrological storm-water flows. The large combined infiltration capacity of these LID devices allowed the original proposed storm drain to be deleted from the project. The infiltration features significantly reduce the amount of property and storm run-off, sediments, and pollutants from getting into existing drains that outlet to the ocean and thereby contributes to improved water quality. The Project demonstrates the Department’s commitment to promote sustainable methods in storm-water management and treatment. The Project Team collaborated with the community and stakeholder groups to develop the final design of the project. Public workshops and survey mailings were conducted for increased involvement and constructive input from the local community. The Project construction commenced in mid-2014 and completed in early 2015. Engineering a Sustainable Storm-Water Management System Storm-water capture and infiltration design required hydrological and geotechnical data from the local area. A hydrological study was performed to determine the expected storm-flows in the drainage subarea. Soil testing was conducted within the project limits to obtain ground infiltration rates. The resulting data was used to calculate the size of the underground storm-water infiltration basin and parkway bio-retention planters. The infiltration basin is a configuration of high strength plastic, rectangular, stackable, module units woven with filter fabric. This design provided an opportunity to configure the basin to different shapes to avoid essential subsurface utilities. Permeable pavers, porous concrete sidewalks and gutters at various locations contribute to the infiltration design capacity for the project. The storm-water infiltration basin was sized to have a capacity of 0.134 acre-feet. An estimated annual recharge of 3.75 acre-feet of storm-water is projected for the subarea. Fore-bays were proposed at the upstream end of the bio-retention planters. The fore-bay is an open accessible compartment which allows for sediment and trash from the street gutter to collect prior to flowing into infiltration section of the bio-retention planters. Curb cuts allow flows to divert from residential properties and the roadway gutter into the fore-bay and bio-retention planters for conservation and improved water quality. Flows in the bio-retention planters can infiltrate into the ground surface for natural filtering of pollutants. At the catch basins that lead to the under-ground infiltration basin, filter screens for sediment and pollutant removal were installed The entire LID system was successfully tested during a major storm event in December 2014. At the upstream ends of the project, runoff at gutter depths that ranged from 3 to 6-inches entered the project area from the adjacent streets. The porous sidewalk worked effectively providing a slip resistant surface without puddles and sheet flows seen on impervious sidewalks. Gutter flows entered the bio-retention planter inlets and debris and trash were intercepted by the fore-bays. Flows from this particular storm were so successfully infiltrated by the porous gutters, sidewalks and bio-retention planters on Green Street that at the downstream end of the block the gutter flow was almost completely eliminated. Path to Sustainable Roadway Design The roadway design was also altered to assume a more sustainable project. The roadway widths were engineered to be compatible with adjacent streets and also allow room in the parkway to include sustainable bio-retention planters. New sidewalks were designed that meet Americans with Disabilities Act (ADA) guidelines. The sidewalks on Green Street were designed to use porous concrete to allow runoff from the adjacent properties to infiltrate into the ground. Sidewalk and parkways not only provide a safe zone for pedestrians but bridge the gap that existed with the adjacent improved streets. Residents and school children will be able to travel safely through connected neighborhoods. Another sustainable design method is to preserve the existing mature trees such as native California oak and incorporate them into the parkway design. Parkways and planters are adjusted to the provide space for the trees to thrive. The proposed roadway curb was routed around one mature parkway tree so that it would not have to be removed. New ADA-compliant curb ramps with larger curb return radii contribute to improve safety, access, and mobility for local residents. Existing concrete cross gutters were removed to provide a smoother ride through the intersections. Permeable pavers are proposed at the crosswalk locations of the intersections and at the end of the cul-de-sac to provide an aesthetic-enhancing feature to surround the neighborhood. The proposed roadway pavement will use sustainable material for the surface course consisting of a 1 ½-inch rubberized asphalt pavement treatment. This Asphalt Rubber Hot Mix (ARHM) surface consists of 2000 recycled tires for every lane-mile of pavement. ARHM provides a quieter surface ideal for residential areas, resist cracking, and a longer life cycle with virtually no maintenance. The plants and trees chosen for the bio-retention planters are drought-tolerant and native species to handle the semi-arid climate of Southern California. The planters will have curb cuts at the sidewalks and gutter to allow nuisance low flows from the residential properties to enter and enrich the plants. Community Outreach and Stakeholder Input An integral part of successful sustainable design is for active community involvement. Several community meetings were held locally to inform and educate the public about the proposed project. The meetings also provided the Department an opportunity to gather valuable input on the concerns that impact the community. At the meetings, the designers described the project improvements in detail, including the sustainable features. The residents voiced approval of the inclusion of LID components including infiltration features. Several issues were brought forth by the local residents such as local flooding, parking, and high vehicle speeds. Where possible, issues raised were addressed by the design team within the project. The healthy exchange of information provided insight that leads to a more sustainable design. In addition, surveys were mailed to all affected homeowners for their participation and comments. Included in the packet was a brief description of the partnership between the Department and the homeowners for the maintenance of the landscape plants and the cleaning of the bio-retention fore-bay units. Since no irrigation is proposed for the drought-tolerant native plants in the bio-retention planters, the homeowners are requested to maintain plant survival after the establishment period. The fore-bays can be easily swept to remove sediment and trash periodically. Community involvement and commitment generates an active collaboration and cooperation with the Department for a successful sustainable neighborhood.

Submitted by: 

Craig Cline

Title: 

Senior Civil Engineer

Organization: 

Los Angeles County Department of Public Works

Address: 

P.O. Box 1460, Alhambra, CA 91802-1460

Phone: 

(626)458-7983

Fax: 

(626)458-7827

Email: 

CCLINE@dpw.lacounty.gov