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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 Mitigation construction costs are obviously a function of the mitigation design and site characteristics, with typical expensive elements including land purchase, water supply and delivery systems, earthwork, and site preparation. Development of wetlands on upland sites is typically the most expensive form of mitigation on a per-acre basis because of the often extensive earthwork and water supply and delivery costs associated with this mitigation strategy. The restoration of former wetlands and enhancement of existing wetlands can be as expensive as developing new wetlands, but generally these approaches are less expensive because costs of extensive earth moving, site preparation, and water delivery are avoided or are lower. Generally accepted cost guidelines for developing, enhancing, or restoring wetlands are not available. Post construction costs for implementing wetland mitigation measures are not routinely reported in the technical literature. When costs are reported, they are for specific sites and technical designs, and have ranged from about $2,000 to $100,000 per acre. ES's project experience suggests that $20,000 to $25,000 per acre of mitigated wetland represents a reasonable construction cost for creating new wetlands, when the specific mitigation design is undetermined. These costs do not include provisions for long-term monitoring of the mitigation site to assure the permitting agency that mitigation is successfully achieved. Long-term site monitoring to demonstrate compliance with stipulated performance standards (included as permit conditions) is becoming a more common requirement of wetland mitigation. The cost of conducting a monitoring program is dependent on the plan requirements and the frequency with which measurements or site documentation is required. -19- BI6-3-3 ,