Haster Basin is a 200-acre-foot retarding basin located on a 22-acre site in the City of Garden Grove. The Orange County Flood Control District retained AKM to evaluate alternatives and prepare construction documents to enable the basin to attenuate the 100-year expected peak flow from the upstream 2,200 cubic feet per second (CFS) to the downstream channel’s capacity of 400 CFS.

AKM’s scope of work included the preparation of a comprehensive Preliminary Design Report, a Basis of Design Report documenting design calculations and methodology, and the development of plans, specifications, and an engineer’s estimate. The final project incorporated a 460 CFS pump station equipped with three 153.4 CFS mixed-flow pumps, each operated by 845 HP natural gas/LPG engines. The basin was re-graded to increase its volume by 50 acre-feet, and water quality features were implemented in accordance with the County’s Drainage Area Management Plan. Additional site improvements facilitated maintenance access, while joint-use planning allowed the integration of two soccer fields and architectural enhancements to the pump station building, ensuring it complemented the character of the surrounding community. AKM verified hydrologic studies and conducted hydraulic analyses of the East Garden Grove-Wintersburg Channel to confirm that outflow from the basin could be safely conveyed downstream. As part of this effort, AKM designed modifications to a 100-foot section of the channel, increasing its capacity from 400 CFS to 460 CFS. This adjustment reduced the required flood storage volume, making space available for the construction of two soccer fields at the site.

The project also included the construction of 700 feet of a triple box culvert inlet drain, consisting of two 11.5-foot-wide by 6-foot-high sections and a 9-foot-wide by 6-foot-high section. AKM processed the structural design of the pump station, channel modifications, and triple box inlet channel through the County’s Building Department. Additionally, AKM provided engineering services during construction, as well as startup and commissioning of the $26 million project.

The following is an excerpt from an email sent by Vincent Gin (former OC Public Works Project Manager) to Shane Silsby (former Director of OC Public Works) and Kevin Onuma (Deputy Director, OC Public Works Operations and Maintenance) regarding AKM’s performance on the project:
“More than most projects in my experience, the consultant, AKM Consulting Engineers, was especially emotionally engaged in the project. Zeki Kayiran, John Logue, and Glen Deiter are not only technical experts in an esoteric and highly specialized field but performed beyond our expectations. And we learned from them—our knowledge base is now greater than before expressly because of our work with AKM. It was a privilege to work with AKM and witness their high level of competence, and I don’t say that easily about any consultant.”