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<br />4. Work in PrOQress. Where construction of publicly owned, <br />operated and maintained flood control structure will not be <br />completed within 12 months following completion of the <br />report, but adequate progress has been made, the impact of <br />the project shall be included in the hydrologic analysis. <br /> <br />5. Detention. The hydrologic analysis shall consider the <br />effects of on-site detention for rooftops, parking lots, <br />highways, road fills, railroad embankments, diversion dams, <br />refuse embankments (e.g., solid waste disposal facilities), <br />mill tailings impoundments, siltation ponds, livestock <br />water tanks, erosion control dams, or other structures <br />only if they have been designed and constructed with the <br />purpose of impounding water for flood detention and are <br />owned, operated, and maintained by a government body. <br />Detention structures that are randomly located, privately <br />owned, or privately maintained shall not be included in the <br />hydrologic analyses unless it can be shown that they <br />exacerbate downstream peak discharges. <br /> <br />6. Previous Studies. Where appropriate, available <br />floodflow-frequency information shall be used so that <br />previous work by Federal, State, or local agencies shall <br />not be duplicated. Where such data are not available, <br />where conditions have changed significantly, or where the <br />methodologies or data used in previous studies are not <br />appropriate, a new hydrologic analysis for each stream <br />shall be prepared. <br /> <br />A comparison of any proposed discharges with all published <br />or unpublished floodflow- frequency data that exist for the <br />study area shall be provided to the Board. <br /> <br />Proposed flood discharges shall be compatible with those <br />used in previously completed studies on the same <br />watercourse. The results of a later floodflow-frequency <br />analysis shall be considered, where they disagree with <br />discharges used in completed studies, only when they can be <br />shown to be significantly different statistically than the <br />previously used discharges. The test for significance <br />shall be based on the confidence limits of the latest <br />analysis, as described below. <br /> <br />-11- <br />