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PEER REVIEW VALIDATES QUALITY OF RUNOFF MANAGEMENT PLAN FOR 241,
PROTECTION OF WATERSHED
Independent Analysis Says Plan Incorporates Best Design Practices,Will Provide “High Degree” of Water Quality Protection
IRVINE, Calif. (September 3, 2008) – The final runoff management plan for the completion of State Route 241 to connect with Interstate 5 south of San Clemente is an effective system that will ensure that there will be limited change in the flow of sediment after the toll road is built, according to an independent peer review of documents related to the plan which was released today by the Transportation Corridor Agencies (TCA).
The plan is designed to control runoff from the surface of the road and prevent increased erosion. TCA commissioned a third party review of the runoff management plan and of reports prepared by opponents of the project that claim the plan is inadequate.
The San Mateo Watershed is more than 85,000 acres and the route for the extension of the 241 is located on the very western edge of the watershed, adjacent to existing developments in San Clemente. The project footprint is less than three-fourths of one percent of the entire watershed. The source area for the cobbles that are important to the surf break at Trestles is located in the eastern half of the watershed. The area that the 241 traverses does not contain cobble material and the project will not block the flow of the cobbles from the watershed.
Derrick Coleman, Ph.D., from Tetra Tech EC, Inc., who has more than 30 years of experience in hydromodification studies and surface water resource evaluations, including 20 years on projects in California, conducted a peer review and assessment of documents related to the runoff management plan for the 241 extension. Hydromodification is the alteration of water flow through an area. His findings include:
- The TCA design team has proposed an effective system that will minimize the effects from hydromodification and provide a high degree of water quality protection.
- The design team has applied current knowledge of the hydromodification process in order to control such changes (potential erosion) and create the best opportunity to limit their impact.
- “To me this indicates the TCA is committed to providing a roadway design that is as protective as possible of the watershed systems it crosses and to constructing it in a manner that provides the least impact possible.”
- In contrast, Coleman noted that the consultant for the opposition, Philip Williams and Associates (PWA), adopted the role of project opponent, used its knowledge in a negative way and tried to “confuse issues and create uncertainty.”
PWA, who has been hired by the Surfrider Foundation to evaluate the impacts of the toll road on surfing at Trestles, has indicated that it is not correct to compare the footprint of the toll road to the entire 85,000 acre watershed. PWA contends that a more appropriate evaluation is to divide the area the toll road crosses into subwatersheds and then calculate the percentage of impervious areas within each subwatershed. PWA cites references that indicate that with this amount of impervious surface, the sub-sub watershed would destabilize, resulting in additional silt in the watershed, which could potentially impact the flow of cobbles to the surf area. PWA used analysis created by Coleman to make this point. Coleman concludes that PWA oversimplifies discussion of erosion and sedimentation by:
- Focusing independently on potential sources of eroded sediment
- Concluding worst-case scenarios
- Ignoring complexity of sediment delivery system
- Allowing no benefit from control measures
Coleman also disagrees that an increase in fine sediment would reduce the ability of channel flows to carry the very coarse cobbles that are important to surf conditions at Trestles.
Tom Margro, CEO of TCA, said the positive report on runoff management adds to the mounting body of evidence from federal and state agencies and recognized experts on coastal oceanography and surface water resource evaluations that the plan for the 241 is sensitive to the complex needs of the environment. Earlier, the Environmental Protection Agency reported that the proposed route represented the preliminary Least Environmentally Damaging Practicable Alternative (LEDPA) within the meaning of the Clean Water Act. Exaggerated claims by the opponents about damage to the watershed and the impact of sediment flow have now been countered in the detailed peer review conducted by Coleman.
The facts are clear and compelling,” Margro said. “Not only will completion of the 241 reduce gridlock and improve our regional transportation system, its sensitive design protects the watershed, endangered habitats and our beaches. The evidence is overwhelmingly in favor of the U.S. Department of Commerce overturning the California Coastal Commission vote against the extension, which was based on amazing conglomeration of twisted data, distortions and inaccuracies regarding water quality issues.”
In stark contrast to the “Save Trestles” hyperbole, independent analysis shows the 241 plan protects the beaches. Richard J. Seymour, Ph.D., research engineer at Scripps Institution of Oceanography and noted consultant in coastal oceanography, conducted an independent peer review of the documentation relevant to the impact of the toll road on surfing conditions in the vicinity of San Mateo Creek. Based upon a careful review of all the pertinent documents presented, he found that the Corridor would result in no detrimental effects to the surfing in the Trestles area.
Peer Review of TCA Plan
Map of San Mateo Watershed
ABOUT COMPLETING THE 241
Extending the 241 will relieve traffic on Interstate 5 in South Orange County by providing an alternative route. With construction of the toll road, two miles of Interstate 5 will be retrofitted to collect and treat runoff, improving water quality in the Trestles area. Without the toll road, travel from the San Diego/Orange County border to Mission Viejo will take one hour in 2025. With the toll road constructed, the same drive on Interstate 5 will take 25 minutes and it will take 16 minutes on the toll road. The new road will provide an alternative to Interstate 5 for the hundreds of thousands of motorists a day who travel between San Diego, Orange and Los Angeles Counties.
Editor’s Note: Members of the media may contact Dr. Coleman for comment: Derrick.Coleman@tteci.com
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