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I I I I I I I I I I I I I I I I I I I ES ENGINEERING-SCIENCE regulatory personnel are generally willing to accept this approach as effective mitigation. The difference in this case is that the protected and managed wetlands would provide better quality and/or additional values that did not previously exist and that compensate for values that would otherwise be lost with the project. It has been ES's experience that Corps and EP A regulatory personnel in general closely follow the MOA guidelines. Acceptance of a proposed mitigation program or plan can be significantly enhanced if these guidelines are considered and incorporated during its development. The final scope of an approved wetland mitigation plan is determined only after a thorough interagency process of negotiations, plan reviews, and modifications of initial concepts submitted by the project sponsor(s). Negotiations between project sponsors and the agencies usually continue until a mutually acceptable plan is developed. Minimum wetland mitigation requirements typical include acre-for-acre replacement ratios with the focus of the restoration, enhancement, or creation activities centering on the most notable or most important wetland functional values. Basically this approach means that for each acre of wetland lost, a minimum of one acre of the same wetland type must be created (or restored or enhanced) that provides equivalent environmental values (e.g., wildlife habitat) as the acre lost. Location of mitigation sites as close to the impact area as practical is preferred. The Corps and other agencies have substantial discretion in applying these general guidelines, which is where much of the potential negotiations focus. Agency acceptance of a plan can require an average replacement ratio of greater than one to one, especially if high-quality wetlands are to be impacted. Such a decision is based on numerous considerations, with two of the more significant factors being the estimated value of the wetland functions being lost and the probability of successfully achieving effective replacement. Higher replacement ratios can typically range from 15 to 35 to 1. High existing wetland values and low probabilities for successful and effective mitigation would probably generate requests for the higher end of the range. Given current wetland and riparian area characteristics along both Bear and Turkey Creeks, it is very likely that a future project would be required to mitigate for the combined acreage of wetland and riparian areas lost, and that the compensation ratio would be more than one to one. Assuming a minimum acre-for- acre replacement ratio, the mitigation requirement would range from about 34.8 acres for Scenario B to about 50.5 acres for Scenario D. Related Environmental Issues . In addition to potential inundation effects on wetlands and riparian resources, altered lake operations would generate concerns by the FWS regarding stream-flow depletion effects on federally-listed threatened and endangered (TIE) species down stream. The FWS is currently irr.plementing an increasingly more aggressive policy requiring mitigation for streamflow depletions from water development projects in the Platte River watershed caused by any federal action. The policy seeks to minimi7e potential depletion-related impacts to TIE species associated with the Platte River floodplain near Grand Island, Nebraska. Species of prominent concern -15- Bl6-l-3