The massive project to prevent the Santa Ana River from flooding heavily urbanized portions of San Bernardino, Riverside and Orange counties continues to move forward. Orange County is purchasing property in preparation for raising the existing Prado Dam near Chino. Meanwhile federal officials are wrestling with the environmental affects of an already completed dam farther upstream, a dam that environmentalists say will harm three endangered species. The U.S. Army Corps of Engineers' Santa Ana River Mainstem Flood Control Project has been under consideration for about 30 years. The $1.4 billion project began making major strides 11 years ago when the Corps signed an agreement with the counties of Orange, Riverside and San Bernardino. The four entities are splitting the cost, with the federal government paying about two-thirds of the expense, and Orange County providing the largest local share. Corps engineers said the Santa Ana River — which flows through Colton, Riverside, Norco, Anaheim, Santa Ana, Orange, Fountain Valley, Costa Mesa and Huntington Beach — posed the greatest flood risk in the western United States. The Corps estimated that a serious flood could threaten 3 million people and cause $15 billion in property damage. Tens of thousands of homes lie within the floodplain, and homeowners have had to pay for expensive flood insurance. When complete, the Mainstem project will provide at least 200-year flood protection, whereas the previous facilities did not provide even 100-year flood protection for large areas. The project consists of seven interdependent features: o Seven Oaks Dam near the San Bernardino County city of Highland. The 550-foot-tall, $420 million dam is complete, but discussions continue about whether the dam will create a full-time reservoir or only provide flood control functions. The dam could hold about 145,000 acre feet of water. o Mill Creek Levee reinforcement in San Bernardino County. This 2.4-mile concrete wall, atop an existing levee, is in place. o Oak Street Drain in Corona. The 3.3-mile channel from an existing debris basin to Prado Dam is also complete. o San Timoteo Creek channelization. A new sediment detention basin and channel through the cities of Loma Linda, Colton, Redlands and San Bernardino is nearing completion. o Lower Santa Ana River channelization. This 23-mile project involves widening, upgrading and, in some instances, relocating existing channels. Construction of jetties and a straining dike at the mouth of the river between Huntington Beach and Newport Beach, and various bridge improvements are also part of this effort. The work is nearly finished. o Prado Dam enlargement. The dam, near the City of Chino, will be raised 28 feet, and levees, dikes and the spillway will be upgraded. At an estimated $250 million, this is the second most expensive part of the flood control project. o Santiago Creek Reservoir. The Corps will turn an old gravel pit in eastern Orange County into a reservoir, and will improve creek channels. The overall project is scheduled for completion in 2006, according to Corps spokesman Herb Nesmith. The project also involves acquisition and/or maintenance of a few thousand acres of habitat in various places — including 92 acres of salt marsh restoration, maintenance of 1,100 acres of floodplain below Prado Dam, and 764 acres of habitat below Seven Oaks Dam for the Santa Ana River woolly star, an endangered plant. While the Corps argues that the environmental mitigations are extensive, environmentalists are not satisfied. The Center for Biological Diversity sued the Corps over Seven Oaks Dam's impacts on three endangered species — the woolly star, the slender-horned spineflower and the San Bernardino kangaroo rat. The U.S. Fish & Wildlife Service raised the species issues six years ago, and the Center threatened to sue three years ago, but the Corps "essentially dragged their feet until the dam was built," said Noah Greenwald, a conservation biologist for the Center. In August, the Corps issued a biological assessment for the dam, which the Fish & Wildlife Service is now reviewing, said P.J. White, branch chief for the Service's San Bernardino County office. White said he was still going through the document. His agency has until about the end of the year to issue its "biological opinion," which could lead to further mitigations. The status of the kangaroo rat has declined since the federal agency listed the species as endangered about three years ago, White said. "We're very concerned about the kangaroo rat and certainly the Seven Oaks Dam affects the largest population of the rat that is in existence," White said. Greenwald said the Corps' latest biological assessment basically proposes the same mitigations as contained in reports from the late 1980s. The two rare plants and the kangaroo rat are all dependent on flooding, which the new dam will prevent, he said. "I would like to see flood-like conditions re-created as much as possible in the wash," Greenwald said. The Corps also should purchase mining rights in the wash and acquire habitat elsewhere. These mitigations, however, are expensive. Greenwald said the entire project is "symptomatic" of Southern California's approach to flood control, which so often replaces biologically diverse habitat with concrete and rip-rap. Meanwhile, preparations for the Prado Dam enlargement continue, according to Elayne Rail, chief of real estate and financial planning for the Orange County Flood Control District. Officials are still refining project details and completing environmental documents, including a biological opinion by the Fish & Wildlife Service, she said. Once that work is complete, the county and Corps should be able to sign a project agreement, probably in January, she said. Once an agreement is in place, work would begin almost immediately on the $250 million project, for which the county and the Corps will split costs equally. Rail estimated the Prado Dam construction would take five to six years. Contacts: Herb Nesmith, U.S. Army Corps of Engineers, (213) 452-3921. P.J. White, U.S. Fish & Wildlife Service, (760) 431-9440. Noah Greenwald, Center for Biological Diversity, (520) 623-5252. Elayne Rail, Orange County Flood Control District, (714) 834-6000.