LID TREATMENT CASE STUDY BRANSTEN ROAD, SAN CARLOS Analette Ochoa, P. E. , QSD/P, To. R, WRECO May 22, 2013
LID Treatment Case Study. Bransten Road Project Description Conceptual Design with Three Alternatives Design Parameters- MEP vs. C. 3 Challenges 2
Project Description Clean Watersheds for a Clean Bay (CW 4 CB) Industrial Site Location chosen to evaluate potential PCB load reductions 977 Bransten Road – “Hot Spot” t ns ra ty un Co B d ld O en oa d a Ro l. R ria st du In San Carlos ad Ro 3
Treatment BMP Concept Considered Three Treatment Alternatives Both sides Underground treatment/ maximize parking At hot spots 4
Treatment BMP Concept – Alternative 1 and 3 5
Treatment BMP Concept – Alternative 2 6
Treatment BMP Concept Alternative 3 chosen for cost-effectiveness 7
Treatment BMP Concept Watershed Map 15. 6 ac 8
Treatment BMP Concept $$ Utilities/Potholing Cost effectiveness comparison: $/sq ft of treatment Public meetings: Input from property owners 9
Design Parameters 9 Bioretention Swales in Bulb-outs 10
Design Parameters - MEP Need for parking vs. need for WQ improvements Roadway watershed vs. off-site Reduced width from 8’ to 6’ to avoid gas line conflict Underdrain vs. no underdrains 18” vs. 12” deep bioretention soil Temporary vs. permanent irrigation 11
Special Design Parameters 16” deep curb - stability analysis against overturning or sliding Impermeable liner -protection of roadway and utilities Bulb-out Radii Consideration for trash/sediment accumulation Industrial site - Truck turning radius Irrigation Ordinance - low flow sustainable design Planting - smaller trees due to utility conflicts 12
Challenges Utility conflicts Urban Area Water Main Sewer PG&E Gas Design considerations Impermeable liner Deeper curb on roadway side Concerns with differential settlement 13
Challenges Soils 8 borings HSG D Hazardous soils Groundwater 5. 5 - 7. 5 ft 14
Challenges Flat area - Minimum hydraulic head, no drainage system Underdrain vs. no underdrain Planting of trees 15
Summary of Bioretention Areas Conceptual: 43 parking spaces and 6, 920 sq ft of bioretention area, and 3. 57 ac (155, 700 sq ft) of treatment Final: 40 parking spaces and 4, 540 sq ft of bioretention area, and max 2. 61 ac (113, 491 sq ft) of treatment 16
Bransten Road - Lessons Learned Coordinate with utility companies early Inform utilities of project goals (compaction) Obtain schedule for review/comment period Pothole Understanding planting goals with utility clearances (overhead/underground) Hold public meetings to get approval from adjacent property owners or companies for parking needs 17
QUESTIONS 18
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