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Worksheet E <br />Hydromodification Management <br />E-1 Is the project a Hydromodification17 Management (HM) Project? <br />E-1.1 Is the total impervious area increased over the pre-project condition? <br />Yes. Continue to E-1.2 <br />No. Go to Item E-1.3 and check “No.” <br />E-1.2 <br />Yes. Go to E-1.3 and Check "Yes". <br />E-1.3 Is the project a Hydromodification Management Project? <br />No. The project is EXEMPT from HM requirements. <br />E-2 Incorporate HM Controls (if required) <br />Are the applicable items provided with the Plans? <br />Yes No NA <br />► If the project is subject to the HM requirements, incorporate in the project flow duration control measures designed <br />such that post-project discharge rates and durations match pre-project discharge rates and durations. <br />► The Bay Area Hydrology Model (BAHM) has been developed to help size flow duration controls. See <br />www.clearcreeksolutions.info/downloads. Guidance is provided in Chapter 7 of the C.3 Regulated Projects Guide. <br />Is the site located in an HM Control Area per the HM Control Areas map (Appendix H of the C.3 Regulated Projects <br />Guide)? <br />No. Attach map, indicating project location. Go to Item E-1.3 and check “No.” <br />Yes. The project is subject to HM requirements in Provision C.3.g of the Municipal Regional Stormwater <br />Permit. <br />17 Hydromodification is the change in a site’s runoff hydrograph, including increases in flows and durations that results when land is developed (made more impervious). <br />The effects of hydromodification include, but are not limited to, increased bed and bank erosion of receiving streams, loss of habitat, increased sediment transport and/or <br />deposition, and increased flooding. Hydromodification control measures are designed to reduce these effects. <br />Site plans with pre- and post-project impervious surface areas, surface flow <br />directions of entire site, locations of flow duration controls and site design <br />measures per HM site design requirement <br />Soils report or other site-specific document showing soil type(s) on site <br />If project uses the Bay Area Hydrology Model (BAHM), a list of model inputs and <br />outputs. <br />If project uses custom modeling, a summary of the modeling calculations with <br />corresponding graph showing curve matching (existing, post-project, and post- <br />project with HM controls curves), goodness of fit, and (allowable) low flow rate. <br />If project uses the Impracticability Provision, a listing of all applicable costs and a <br />brief description of the alternative HM project (name, location, date of start up, <br />entity responsible for maintenance). <br />If the project uses alternatives to the default BAHM approach or settings, a written <br />description and rationale. <br />7.A. - Page 63 of 121 <br />69