Storm Drainage and Hydrology
Pakpour Consulting Group provides comprehensive storm drainage solutions including hydrology and hydraulic analysis and Flood Control System Optimization. Pakpour Consulting Group has completed several high-profile storm drainage projects, which included the preparation of design plans and specifications for flood control channels and creek embankment upgrades. Recently the State Water Resources Control Board (SWRCB) adopted and issued significant changes to the new Construction General Permit (CGP) affecting all construction projects throughout California. With two registered Qualified Storm Water Pollution Prevention Plan (SWPPP) Practitioners (QSP) on staff, Pakpour Consulting Group provides support services to assist agency staff with identifying specific recent and future changes to the new CGP that may require incorporation into agency procedures when planning and constructing future capital improvement, operation & maintenance, and emergency-repair projects.
Cupertino Road Storm Drainage Improvements
City of Cupertino | Cupertino, CA
Situation: The City of Cupertino required assistance in identifying options to relocate an existing storm drain line which was located on private property and prone to flooding. The storm drain line drained an area of more than 70 acres. The goal of the project was for the new storm drain line to be able to carry a design storm event and be located in public right-of-way.
Special Challenges: Pakpour Consulting Group (PCG) was initially tasked with preparing a hydrologic model of the existing 71.3-acre drainage basin and public piped storm drainage system. After the preferred option was identified by the City, PCG conducted extensive research of existing and former utilities within the project area. Research efforts included coordinating with each respective utility agency, including the City, Cupertino Sanitary District, PG&E, Telephone, Cable, Fiber Optic, Santa Clara County Traffic Signal, and San Jose Water Company, to obtain record documents. PCG organized numerous field meetings with maintenance staff to verify existing field conditions, scheduled existing utility investigation operations (electronic probe, ground penetrating radar, and pothole).
Services Overview: Since 2018, PCG has served as on-call engineers. For the Cupertino Road Storm Drainage Improvements, PCG provided design, construction support, and storm water hydrologic services to relocate an older upstream portion of an existing cross-country storm drain collector line. PCG’s services included preparing a drainage study to determine existing system peak runoff flows and provide conceptual relocation options for City review. The preferred option relocated a portion of the existing upstream storm drain collector line to within Cupertino Road and North Foothill Boulevard right-of-way.
About City of Cupertino: Incorporated in 1955, Cupertino is a city within Santa Clara County with a population of more than 58,000. Cupertino is known as the home of Apple, Inc.’s corporate headquarters.
Boris Lake Storm Drain Outfall Repairs
City of Pleasanton | Pleasanton, CA
Situation: Due to an unusually wet 2016/17 winter, the City of Pleasanton (City) experienced a storm drain failure at the system’s discharge location into Boris Lake located within East Bay Regional Parks District’s Shadow Cliffs Regional Recreational Area. The City believed the 55 LF 36-inch corrugated metal pipe (CMP) failed due to surcharged loading and had also severely eroded the 66% slope hillside where it was installed. Time was of the essence to design and construct the repair before the 2017/18 rainy season.
Special Challenges: Given the City’s need to have the storm drain repaired before the beginning of the 2017/18 rainy season, Pakpour Consulting Group (PCG) assembled a team familiar with environmental permitting and geotechnical knowledge of the area to expedite the design phase. The overall design was condensed to approximately 1.5 months to account for advertising and construction completion by mid to late October. In order to attain the City’s goal of minimizing the potential of a future pipe failure, the design incorporated the use of 36-inch fusible polyvinylchloride in combination with pipe anchors to ensure pipe stability. The finished grade flattened the existing site from a 1.5:1 to a 2:1 slope and rip rap was placed on the final two feet of the backfill directly over the pipe to minimize erosion should the storm drain overflow from the upstream catch basin.
Services Overview: Since 2013, PCG has served as on-call engineers for the City of Pleasanton. For the Boris Lake Storm Drain Outfall Repairs project, PCG provided design and construction support services for the repair of 55 LF of 36-inch storm drain pipe and reconstruction of the eroded hillside. PCG and its subconsultants also assisted with geotechnical investigations/reports and environmental permitting. PCG worked close with the City and various permitting agencies to expedite the project to ensure completion before the 2017/18 rainy season.
About City of Pleasanton: Incorporated in 1894, Pleasanton has a population of more than 70,000. In 2005 and 2007, Pleasanton was ranked the wealthiest middle-sized city in the United States by the US Census Bureau.
Citywide Storm Drain Upgrades
City of Berkeley | Berkeley, CA
Situation: Intersections in the flatlands of western Berkeley were prone to flooding even with moderate rainfalls. The existing infrastructure, which consisted of undersized siphons with small diameter pipes, clogged during rain events exacerbating the flooding at intersections and nearby garages. The City identified six of the worst flood prone intersections and turned to a trusted partner to find a solution. The project sites were located at:
Hearst Avenue at Sixth Street
Curtis Street at Francisco Street
Jones Street at Tenth Street
Stuart Street at California Street
Bancroft Way at Bolivar Drive
Cragmont Avenue at Regal Road
Special Challenges: The existing topography is virtually flat making infrastructure changes challenging. In addition, the new infrastructure needed to connect to the existing shallow storm drain system downstream. Pakpour Consulting Group (PCG) investigated various water conveyance methods through the intersection. Some project sites replaced the shallow siphons with wide valley gutters while other sites utilized shallow conventional storm drain systems. Due to extreme slope tolerances, PCG meticulously investigated the existing utilities during design to ensure no conflicts and to avoid relocation. PCG coordinated the valley gutter designs with the City Bicycle Coalition to ensure smooth transitions. Upon project completion, all six sites successfully handled storm events with minimal to no flooding.
Services Overview: Since 2013, PCG has served as on-call engineers for the City of Berkeley. For the Citywide Storm Drainage Upgrade Project, PCG provided full design and construction support services for the reconstruction of the roadway and storm drains at six different sites, including pavement repair, correcting drainage patterns, installing new storm drain infrastructure, and coordination with multiple stakeholders including residents and City commissions.
About City of Berkeley: Located on the eastern shore of San Francisco Bay with a population of more than 120,000, Berkeley is a center for academic achievement, scientific exploration, free speech, and the arts.
