Orange County Branch Newsletter

November 2011

Career Collectibles

Back to the Sixties in Orange County

Carl Nelson, P.E.

Ironically, my first year with Orange County Flood Control District (OCFCD), 1960-1961was the driest on record until superseded by another dry year 2006-2007. Initial work involved design of small structures on Laguna Canyon Channel, Haster Retarding Basin and the Red Hill Channel all under the supervision of Elmer Christiansen and John Huntsman. Both had extensive experience with Los Angeles County Flood Control District (LACFCD) before coming to OCFCD and were excellent mentors. I was a novice in flood design having only recently completed evening classes in hydraulic engineering USC. Instructors included among others, Erv Spindel Director of Public Works at Downey, Bob White City Engineer of Burbank and a Mr. Bargman, design chief for Los Angeles City’s Hyperion Treatment Plant.

When assigned to design of the San Juan Creek Channel, Elmer took me on a field reconnaissance from Camino Capistrano to Coast Highway. What an interesting day as we walked (and crawled) the dry wash paralleling the Santa Fe railroad tracks. 

There was no incised waterway, only  alluvial sandy creek bed, wooded with dense riparian growth. Occasional migrant worker camps were found along the way serving adjacent crop land.

Hydrologic design was based on the 1955 Engineers Report of Harrison & Woolley, adopted by the Board of Supervisors, approved by narrow of margin (66.7%) of countywide voting for the $43 million bond issue. The approved policy: “Main control facilities to handle the runoff from a storm that may reasonably be expected to occur not more often than once in about 25 years in the flat urban areas…” The approved funding provided only for right of way purchases along with construction of “Earth channel sections…which should serve…until…ultimate area development is reached in the future.”  Existing highway bridges would be adapted to the flood channel improvements.

Given the design flow rate (50,000 CFS) for the combined flows of San Juan and Trabuco creeks we soon found the natural slope produced supercritical velocities, too erodible for the planned earthen channel. This was further compounded by the probability of unstable flow; a hydraulic jump upstream, subcritical flow through the confluence, followed by drawdown through critical depth and return to supercritical downstream. 

Whoa! Few of us can remember the state of computing technology in the 1950s. Slide Rules were “state of the art” and “rounding” was acceptable until I was introduced (at Caltrans) to the  mechanical calculator shown below.

At OCFCD in the sixties we had an electromechanical version of the Monroe!!! Nonetheless, repetitious calculation of the Pressure plus Momentum (P+M) equations was time-consuming and tedious. Decades later we’ve  learned that some of our younger engineers using their new-fangled computer programs might not realize how the field view of rough-water compares with the digital printout of  “glassy smooth” water surface. 

Due to the obviously erodible flood velocities, it was determined necessary to augment the meager bond funds in order to finance a modest concrete slab bank protection while preserving the sandbed of the creek for groundwater replenishment. Even so, the 4 ft. deep concrete toe has proven vulnerable to deep scour with structural failures during major flood events.

Now, under a newer hydrologic design policy, OCFCD is proceeding to construct in stages a program of more durable (and expensive) sheet pile walls which will also increase channel capacity to the modern “100 year” flood.

The city of San Juan Capistrano was incorporated in 1960 and development of the floodplain adjacent San Juan Creek commenced with Jack Kubota, a local consultant as City Engineer. Other city engineers of the era included Chuck Handy of Garden Grove who would become the first chairman of the Orange County City Engineers Association in 1965. I was privileged to attend the monthly meetings representing OCFCD, and Ted McConville represented OC Road Department. Other city engineers of the time included Jim Wheeler of Huntington Beach, Harry Pappas of Westminster, Hugh Foreman of Santa Ana, Bob Ledendecker of Tustin, Thorny Piersall of Anaheim, Hugh Berry of Fullerton, Bud Yaberg of Buena Park, Gary Johnson of Orange, Wayne Osborne of Fountain Valley, Joe Devlin of Newport Beach, and George Madsen of Costa Mesa.

As suburban development of central Orange County expanded in the early sixties, the private engineering sector prospered. Los Angeles area firms; i.e., Voorheis, Trindle & Nelson, Inc. Pearson Associates and others moved in to compete with established local firms such as Boyle Engineering, Lowry Associates, Williamson & Schmid, and others. “Startup firms” included Toups Engineering, Hall & Foreman, Don Greek Associates, Willdan Engineering.

Concurrently, the Orange County Board of Supervisors in lieu of expanding in-house engineering staff began to accept design engineering proposals from qualified private firms. Eventually the design engineering workload of flood and roads would be outsourced about 50%, strictly selecting only firms located within Orange County.

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