STORMWATER MANAGEMENT REPORT FOR TAVARES EAST DISTRIBUTION SUBSTATION

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1 STORMWATER MANAGEMENT REPORT FOR TAVARES EAST DISTRIBUTION SUBSTATION (Lake County, Florida, Section 29, Township 19S, Range 26E) Prepared by: Duke Energy Florida, Inc Exchange Place NP3A Lake Mary, Florida Certificate of Authorization No. EB (407) Fax (407) July 2013

3 Tavares East Distribution Substation Stormwater Management Report 1.0 Project Introduction The 1.85-acre project site lies within the City of Tavares at the intersection of SR441 and Texas Avenue. The project is proposed as a new 69kV to 13kV Distribution Substation. The proposed development will consist of constructing the substation yard, access driveway/parking lot and stormwater areas. 2.0 Soils The following soil information was obtained from the Soil Survey of Lake County, Florida, USDA, Soil Conservation Service. As shown on the Soils Map in Appendix A, the project area consists of the following soil types. The hydrologic soils classification (HSG) of each soil is listed below. Soils Type HSG (8) Candler Sand A (41) Pomello Sand A 3.0 Predevelopment Conditions The existing site is currently vacant with some tree cover. The project Exhibit s in Appendix A depicts the site location and characteristics in the predevelopment condition. The topography on the site ranges from elevation 77.0 NAVD on the south-eastern side of the property to elevation 75.0 NAVD on the north-western side of the property. An evaluation of subsurface conditions was prepared by Ardaman & Associates, and is included under separate cover. There are no wetlands on the property. 4.0 FEMA 100-Year Floodplain According to FIRM No C0361E, dated December 18, 2012; the entire site lies in Flood Hazard Zone X. Please see Appendix A for the FIRM Map. Duke Energy Florida, Inc. 3 k:\wood\projects - current\tavares east d2\drainage\report\tavares east storm report.docx

4 Tavares East Distribution Substation Stormwater Management Report 5.0 Post-Development Conditions The proposed stormwater management system consists of two dry retention areas. The first dry retention area is located within the substation yard itself. This dry retention area will provide water quality treatment and attenuation for the substation yard and surrounding area between the substation fence and property line. The dry retention area will contain the entirety of the 25-year, 24-hour storm event with no discharge. The yard will have a bottom at elevation and a berm at elevation 76.30, and will be filled with 6-inches of #57 granite. Storage within the gravel area has been adjusted based on a 40% void ratio as determined appropriate by the Geotechnical Engineer. Please see letter from Ardaman & Associates in Appendix G. The second dry retention area will be the Dry Retention Pond on the north side of the site. This dry retention pond will provide water quality treatment and attenuation for the driveway area and the area between the northern substation fence and the northern property line. The dry retention pond will contain the entirety of the 25-year, 24-hour storm event with no discharge. The Perc Pack was used with the ICPR model to show infiltration during the 25- year, 24-hour storm event for both basins. The infiltration rates calculated for DRI-1 and DRI-2, by Ardaman & Associates, Inc, were 40 and 70 feet per day, respectively. The infiltration rate used during modeling was 10 feet per day. The seasonal high groundwater elevation used was elevation 71 feet. This was determined by finding the highest elevation of encountered groundwater from the soil profiles, which was elevation 67, and added four feet per Ardaman s recommendation. All the parameters for the groundwater nodes and percolation links were discussed with and approved by Ardaman & Associates. Please see Appendix C, D and E for the Post-Development data and results. Recovery will occur through percolation only for both dry retention areas. To Duke Energy Florida, Inc. 4 k:\wood\projects - current\tavares east d2\drainage\report\tavares east storm report.docx

5 Tavares East Distribution Substation Stormwater Management Report show each pond recovers within the 72-hours following the 25-year, 24-hour storm event, hydrographs are provided in Appendix F. Each pond recovers well within the 72-hours following the 25-year, 24-hour storm event. 6.0 Additional Permitting Information Duke Energy Florida, Inc. will be the responsible entity for the operation and maintenance of the onsite stormwater management systems. Maintenance includes regular mowing of the retention pond banks and the removal of debris. Potable water service and sanitary sewer service for the proposed site will not be required. The Contractor is responsible for constructing the perimeter silt fences and turbidity screens utilizing best management practices to avoid soil erosion during construction. The Contractor is also responsible for providing temporary stormwater management when necessary, during construction. Duke Energy Florida, Inc. 5 k:\wood\projects - current\tavares east d2\drainage\report\tavares east storm report.docx

6 Tavares East Distribution Substation Stormwater Management Report Appendix A Tavares East Distribution Substation Site Exhibits Progress Energy Florida, Inc. k:\wood\projects - current\tavares east d2\drainage\report\tavares east storm report.docx

13 Tavares East Distribution Substation Stormwater Management Report Appendix B Tavares East Distribution Substation Predevelopment Drainage Predevelopment Basin Map Basin Data Node Diagram Node Max Report Basin Summary ICPR Input Report Progress Energy Florida, Inc. k:\wood\projects - current\tavares east d2\drainage\report\tavares east storm report.docx

21 Tavares East Distribution Substation Stormwater Management Report Appendix C Tavares East Distribution Substation Post Development Drainage Post-development Basin Map Basin Data for Basin Post-1 and Post-2 Progress Energy Florida, Inc. k:\wood\projects - current\tavares east d2\drainage\report\tavares east storm report.docx

25 Tavares East Distribution Substation Stormwater Management Report Appendix D Tavares East Distribution Substation Post Development Drainage ICPR Routing for 10-Year, 24-Hour Storm & Mean Annual Storm Node Diagram Node Max Report Basin Summary Input Report Progress Energy Florida, Inc. k:\wood\projects - current\tavares east d2\drainage\report\tavares east storm report.docx

33 Tavares East Distribution Substation Stormwater Management Report Appendix E Tavares East Distribution Substation Post Development Drainage ICPR Routing for 25-Year, 24-Hour Storm Node Diagram Node Max Report Basin Summary Input Report Progress Energy Florida, Inc. k:\wood\projects - current\tavares east d2\drainage\report\tavares east storm report.docx

40 Tavares East Distribution Substation Stormwater Management Report Appendix F Tavares East Distribution Substation Post Development Drainage Recovery Analysis Node Dry Pond 25-Year, 24-Hour Hydrograph Node Sub 25-Year, 24-Hour Hydrograph Progress Energy Florida, Inc. k:\wood\projects - current\tavares east d2\drainage\report\tavares east storm report.docx

45 Tavares East Distribution Substation Stormwater Management Report Appendix G Tavares East Distribution Substation #57 Granite Study by Ardaman & Associates, Inc. Progress Energy Florida, Inc. k:\wood\projects - current\tavares east d2\drainage\report\tavares east storm report.docx