Ellie Encinas and Girish Desai inspect progress on modifications to Prado Dam’s downstream face. Construction on the new outlet works continues in the background.

Motorists have a new distraction at the intersection of the two Southern California freeways, where San Bernardino, Orange and Riverside counties meet. The 63-year-old dam is undergoing an extreme makeover that began about a year ago with a $67.4 million contract awarded to Yeager-Skanska, Inc. The modifications resulted from studies that reveal Prado Dam could not provide its intended level of flood protection. Numerous changes to the surrounding landscape (such as the increased construction of homes, businesses, malls and roads that reduce the area’s ability to absorb rain water and urban runoff, especially upstream) are the underlying factors for the update. Prado Dam is a major component of the Santa Ana River system upgrade, which runs from the Pacific Ocean near Huntington Beach to Seven Oaks Dam at the foothills of San Bernardino Mountains near Highland.

Construction workers place concrete to form the new outlet works in Prado’s more-than-100-foot deep temporary notch. The upgrade will more than triple the dam’s ability to discharge water downstream safely.

“As long as Congress keeps approving the funds and the Orange County Flood Control District acquires the necessary real estate,” said Girish Desai, who manages the project for the Corps, “we expect to finish everything by 2011.” Desai cautioned that those factors are contingent on many outside influences.

Ellie Encinas, the Corps’ Resident Engineer on the project, echoed that concern. “The current construction faces many challenges over the next 2 1/2 years,” she said, “primarily with funding shortages of about $13 million this fiscal year. The current construction funds will be exhausted in mid-June 2004. This will have a significant impact on construction progress, leaving a big hole in the ground and up to 2/3 of the embankment filled.”

Amid a maze of rebar and plywood, workers begin the process of placing concrete that will form the heart of Prado’s internal workings.

The Corps’ knowledge and experience continues to pay dividends with the contributions from LA District's Planning and Engineering divisions. “Doug Chitwood, Bill Halczak, Steve Vaughn and Hayley Lovan have helped Yeager-Skanska reduce potential cost and time impacts and deliver a quality product,” Encinas said.

At a recent visit to the site, Encinas and Desai surveyed the progress from high above the 108-foot notch cut into the dam’s eastern end. Amid a maze of sculpted rebar, workers placed concrete into molds. The structure will funnel water from six intake gates (roughly 10’ by 15’) into two discharge conduits (22’ by 23’ and 600’ long). Once the conduits are complete, earth workers will backfill the notch and contour it to match the upgraded dam’s embankments.

A worker fastens rebar that will strengthen the dam’s inlet works. Prado’s control gates will be installed nearby.

The contractor will place about 150 tons of new rock on Prado’s downstream face; the upstream face will remain essentially unchanged. Raising the dam and tying it into the previously built western end will increase the crest from 2,280 feet to 3,050 feet. By the time the project is complete, Prado’s downstream face will have received 1.5 million cubic yards of new earth material.

What could well be the last big dam project by the Corps involves the agency’s usual combination of people, machinery and vision. Scrapers, ‘dozers and compactors scurry across the top of the dam like so many gigantic insects, each trip adding nearly undetectable quantities that, when taken together, have forever altered Prado’s appearance.

In Prado’s case, beauty is more than skin deep.