Providing Flood Protection for Maricopa County Residents

Homes in the Meridian Pointe Subdivision in unincorporated Maricopa County, Arizona, were at risk of flooding in the event of a 100-year storm event.  Stanley Consultants designed a solution with an 80-acre detention basin.  Unfortunately, the basin provided an issue itself because the site contained multiple earth fissures which could undermine the basins ability to retain water.

This problem was solved by burying a geomembrane three feet deep into the slope of the basin that acts as a barrier between the water and potential earth fissures.  To our knowledge this type of fissure mitigation has never before been applied to a flood control basin project. 

Stanley Consultants provided pre-design efforts including alternatives development, evaluation and assessment; value engineering; final design, preparation of the construction documents, and post-design services.

The final design included a series of cut-off walls between the basin and downstream of the encroaching fissure, and used excavation spoils to redirect surface runoff away from the fissure.  On the down-stream side of the project, a vertical concrete cut-off wall was constructed.  Controlled Low Strength Material (CLSM) was used in the place of concrete throughout the project.  It is a low-strength concrete that is low-cost, easy to install, and can be used for non-structural purposes.

All structures were designed for future regional multi-use.  A innovative stepped drop inlet structure could also double as an amphitheater.  The bottom of the basin can be used in the future for baseball diamonds, soccer fields, walking trails, or other recreational features.

The goal of this project was to implement a flood control feature that would mitigate the regional 100-year flood, be an amenity to the area, be context-sensitive with its surroundings, provide multi-use potential, and be fairly easy to maintain.  All of these goals were met.