Completed Seven Oaks Dam - Up Stream View

Energy Dissipation Pool - Down Stream of Diversion Tunnel

Pervious Material Collection Area - Down Stream of Dam - 16 Million Cubic Yards of Material Removed

Non-Pervious Material Collection Area - East of Dam - 6 Million Cubic Yards of Material Removed

Overview

The Santa Ana River Mainstem Project is designed to provide flood protection to the growing urban communities in Orange, Riverside and San Bernardino Counties. The proposed improvements to the system cover 75 miles, from headwater of Santa Ana River east of the city of San Bernardino to the mouth of the river at the Pacific Ocean between the cities of Newport Beach and Huntington Beach. The project will increase levels of flood protection to more than 3.35 million people within the three county areas. The project includes Seven independent features: Seven Oaks Dam, Mill Creek Levee, San Timoteo Creek, Oak Street Drain, Padro Dam, Santiago Creek and Lower Santa Ana River.

The project will provide for environmental features including enhancement of a degraded marsh area at the mouth of the river, thereby providing significant value as wetland habitat for migrating waterfowl, including the California least tern, a federally listed endangered species.

Increase recreational opportunities will be provided through related developments on the lower Santa Ana River and Santiago Creek.

Funding:

Congress authorized Santa Ana River Mainstem Project for construction in 1986 under new guidelines for cost sharing of water resources projects between Federal and local governments. The local sponsors must pay between 25% and 50% of total cost of the project with the remaining cost provided by the Federal government.

Project Elements:

Drainage area 177 sq.mi.

Dam

Crest Elevation 2610 ft.
Maximum height above 550 ft.
Streambed Crest lenth 2980 ft.
Free board 5.9 ft.

Reservoir

Area at spillway crest - 780 acre
Gross capacity 145,000 Ac.ft.

Storage allocation below spillway crest

Flood control 113,600 Ac. ft.

Spillway

Crest elevation 2580 ft.
Sedimentation (100-years) - 32,000 Ac.ft.
Crest length 500 ft.

Reservoir Design (General storm)

Elevation of max Water surface - 2604.4 ft.
Total volume 115,000 Ac.ft.

Outlet works (gated conduit)

Diameter of conduit 18 ft.
Diameter of penstock 11 ft.
Length of conduit 1623 ft.
Intake Elevation 2265 ft.
Peak outflow 174,000 cu.ft.
Peak inflow 85,000 cu.ft./sec
Peak outflow 7,000 cu.ft./sec

Probable Maximum flood (general storm)

Total volume 356,000 Ac.ft
Peak inflow 180,000 cu.ft./s

In 1862, The largest Santa Ana River flood on record caused about 20 deaths in the region, which was then sparsely populated but now is the three county areas.

In 1938, Flood wiped out roads, bridges and railroads near the river when an 8-foot wall of the water swept out of the Santa Ana Canyon after several days of heavy rains. More than 100 people died in the three county areas. The most recent Santa Ana flood, in 1969 caused five deaths and more than $30 million in damage.

The Santa Ana River Mainstem Project includes the Seven Oaks Dam as a major feature. Seven Oaks Dam accounts for about $420 million of the total $1.4 billion project cost. Two large water districts, Riverside and San Bernardino County, recognized that a Dam also could be used to conserve water and save money. A study showed, store floodwater of the Dam would provide a minimum average of about 10,000 acre-feet of water per year, which is worth about $1 million. The Dam is made of 38 million cubic yards of dirt rock and clay that will form ten mostly vertical zones. These zones will help control the water while protecting the integrity of the dam. The pervious material acts as drain-channeling water out of the dam, while zones of impervious material keeps the water out. The Dam will be able to resist an earthquake measuring 8.0 on the Richter scale, with any point able to sustain a displacement of four feet without causing any overall structural damage.

The construction contract was awarded in the Year 1994, Construction began in May 1994 with completion date targeted to August 1999. To transport pervious and impervious materials to the site, an elaborate 3.5 mile-long (10Km) conveyor system was erected, capable of carrying 3400 tons per hour. The conveyor system eliminates the need for heavy trucks, providing both cost and time efficiencies. It also increases safety on the job site and reduces environmental impact, due to decreased traffic. The productivity and efficiency required to complete one of the highest profile projects in the nation in just five years would be nearly impossible without robotic surveying. It has allowed the crew to cover more ground, faster, with less labor hour.

For Seven Oaks Dam TOUR INFORMATION to contact BARBARA McCULLOUGH

Telephone number 909 794 7704 Represented by Army Corps of Engineers.