Detention Basins
  Tucson Drainage | Upper Duck Creek | Etiwanda Debris Basin

Tetra Tech provided the final design of a 618-acre-foot debris basin in San Bernardino County.  The project sponsors include the County Department of Public Works, the City of Rancho Cucamonga, and the Bureau of Reclamation.  The basin is situated on the Etiwanda Creek alluvial fan and consists of collector levees, a grouted stone drop inlet structure, a 50‑foot‑high embankment, an overflow PMF concrete spillway, an outlet works with turnout structures for water spreading, and a concrete channel downstream of the embankment.
 
Tetra Tech made several recommendations to improve on the original design including designing the spillway for the probable maximum flood instead of the 1000‑year flood, optimizing the spillway/embankment configuration, and shortening the basin to reduce excavation quantities.  These changes improved the level of protection to the embankment and resulted in savings of over $2 million to this $11 million project.  The design required coordination with the State of California Division of Safety of Dams to obtain their approval.  Tetra Tech will provide bidding assistance and engineering support during construction.