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impacts your project could cause to the river system and neighboring <br /> properties. <br /> According to the USGS, the unauthorized "U" structure that was installed in <br /> March 2005, has raised the flood stage by approximately 1000 cfs. Raising <br /> the flood stage can cause irreversible damage to private and public property <br /> along with the potential of drastically altering the flow regime and creating an <br /> unstable river system. A problem that occurs with the use of concrete <br /> structures, such as the constructed "U" structure, is that the structure is <br /> difficult to fix or change. In addition, no structure in an active stream is <br /> permanent, therefore, in the event that the structure should fail, it would result <br /> in large angular concrete particles that have the potential to significantly divert <br /> flows or create erosive conditions to adjacent property. Please identify <br /> proposed corrective measures that will be used to lower the flood elevation to <br /> its pre-construction elevation and a long-term maintenance plan for both the <br /> proposed and constructed structures to ensure that the project does not cause <br /> unexpected degradation to the river. An appropriate maintenance plan may <br /> include an agreement in perpetuity between the Town and a third party for <br /> monitoring and maintenance of the structure. <br /> c. Biologic Impacts <br /> One of the proposed project purposes is to "enhance aquatic habitat <br /> characteristics through the reach," however, your permit application does not <br /> include biological information within the project areas. Biological information <br /> should include, an inventory of macro and micro invertebrates within the <br /> stream along with a description of the riparian community that would be <br /> affected by the proposed work. Please submit information regarding the <br /> existing conditions of the river, and a description on how the project will <br /> enhance the existing aquatic habitat. This office is concerned that the use of <br /> grout and hard bank stabilization will reduce the quality of aquatic habitat <br /> rather than enhance it. Please submit either modified plans that incorporate <br /> bioengineering stabilization practices along with in-stream structures that will <br /> enhance the aquatic habitat without he use of grout, or scientific information <br /> supporting the idea that the project as proposed will truly enhance the aquatic <br /> habitat. <br /> d. Water Quality Impacts <br /> If the structure is not designed correctly it can cause an accumulation of <br /> sediment behind the structure. It appears this may have occurred behind the <br /> structure constructed last March. The accumulation of sediment can cause <br /> water quality problems downstream. Please provide a maintenance plan that <br /> addresses water quality for the proposed structures. In addition, please submit <br /> soil erosion and sediment control plans, including a detailed plan for all <br />