Presented by: y Kit Hamblen CH2M HILL

Size: px

Start display at page:

Download "Presented by: y Kit Hamblen CH2M HILL"

Tyrone Poole
7 years ago
Views:

1 North Fork Peachtree Creek: A Case Study in Urban Stream Restoration A Gwinnett County Watershed Improvement Project Presented by: y Kit Hamblen CH2M HILL

2 Presentation Outline Background Project Overview Existing Site Conditions Project Features Design Methods Construction Challenges Key Elements for Urban Watersheds

3 Project Background Program Goals and Objectives Water Quality Improvement Aquatic Habitat Improvement Public Support Program Strategy Assessment and Planning Project Implementation Implementation ti Funding Sources Stormwater Utility Grant Funding and GEFA Loans Mitigation Banking Site Specific Mitigation Projects

4 Project Background North Fork Peachtree Creek Watershed Tributary to Peachtree Creek and Chattahoochee River Highly Developed eloped Watershed 39 Square Mile Watershed 303d Listed for Fecal Coliform and Fish Biota High Priority subwatershed for watershed improvements

5 Project Watershed Characteristics j g Area = 147 acres Drainage Residential, Commercial and Industrial Landuses Watershed Percent Imperviousness = 62% Georgia Stormwater Management Manual Treatment Needs Water Quality Protection = 2.3 acreacre-feet Channel Protection = 9.6 acre acre--feet Project Objectives Treat stormwater to the maximum extent practical Reduce R d th the TSS lload d from f thi this subwatershed b t h d Restore aquatic habitat through stream restoration and wetland enhancement

6 Site Characteristics RCP Culvert with Sanitary Sewer Conflict Backfilled Oxidation Pond Pl t d with Planted ith Pines Pi Mass Wasting g Erosion on 20-ft High Right Bank Incised and Over-widened Stream Channel Gabion Weirs Exposed Sanitary Sewer Crossing

7 Pre-Construction Site Conditions

8 Pre-Construction Site Conditions

9 Pre-Construction Site Conditions

10 Pre-Construction Site Conditions

11 Pre-Construction Site Conditions

12 Pre-Construction Site Conditions

13 Project Components Stormwater Diversion Structure Rock Walls Sediment Forebay Diversion Channel Wetland Outlet Culvert Replacement Geotechnical Bank Stabilization Buffer Plantings Stream Restoration Maintenance Access Trail

14 Stream Restoration Design Geomorphic Survey of Existing Site and Reference Reaches Natural Channel Design Approach Bankfull Dimensions Riffle: 12 ft Width 1.4 ft Max Depth Pool: 15 ft Width 2.7 ft Max Depth Soil Bioengineering Native Buffer and Wetland Vegetation Elevat tion (ft) Proposed Channel Bed (ft) Water Surface 866 Bankfull Stage (Ft) Station 95.0 Elevatio on (ft) Station (ft) Existing Martin Hts Riffle f Proposed Cross Section

15 Stormwater Wetland BMP Design Features Diversion Structure Normal Max Depth = 3.5 feet Surface Area = 0.75 acres Normal Volume = 0.7 acre-feet Extended Detention Volume = 1.9 acre-feet Captures 25% of Stream Flow at the Diversion Structure Diversion Channel Sediment Forebay Aquatic q Bench (10 feet) Wetland Designed with 3 Depth Zones to Support a Diversity of Aquatic Habitats Removed the First Wetland Cell to Preserve Riparian Buffer Near the Diversion Channel Water Level Control St Structures t Stream Wetland Overflow Pond Outlet (12 Orifice)

16 Project Construction Construction began in April Phases of Construction: Initial Site Preparation and Clearing Culvert Replacement Stream Improvements Upstream of the Wetland Wetland Grading Stream Grading and Stream Structures Wetland Diversion Structure and Channel Wetland Control Structures Geotechnical Stabilization of Stream Bank Access Trails and Buffer Plantings

17 Initial Construction Photographs

18 Initial Construction Photographs

19 Culvert Replacement Photographs

20 Culvert Replacement Photographs

21 Culvert Replacement Photographs

22 Stream Improvements Upstream of Wetland Photographs

23 Stream Improvements Upstream of Wetland Photographs

24 Stream Improvements Upstream of Wetland Photographs

25 Wetland Grading Photographs

26 Wetland Grading Photographs

27 Stream Grading and Stream Structure Photographs

28 Stream Grading and Stream Structure Photographs

29 Wetland Diversion Structure and Channel Photographs

30 Wetland Diversion Structure and Channel Photographs

31 Wetland Control Structures Photographs

32 Wetland Control Structures Photographs

33 Wetland Control Structures Photographs

34 Geotechnical Stabilization of Stream Bank Photographs

35 Geotechnical Stabilization of Stream Bank Photographs

36 Geotechnical Stabilization of Stream Bank Photographs

37 Wetland and Buffer Planting Photographs

38 Wetland and Buffer Planting Photographs

39 Wetland and Buffer Planting Photographs

40 Wetland and Buffer Planting Photographs

41 Key Elements for Urban Watersheds Full Spectrum Urban Watershed Improvement Provide Stormwater Treatment (Traditional\LID BMPs) Divert Stream Flow to Reduce TSS Load from Upstream Runoff Maximize Capture of Local Stormwater Runoff Create Diversity of Aquatic Habitats Multiple l Depth Zones to Support Different Aquatic and Fringe Species Plant Wetland Vegetation as a Food Source and Shelter Restore Streams and Riparian i Buffers Control Stream Grade and Protect Banks to Limit Erosion Grade Channel Cross Section to Enable Floodplain Connectivity Plant Native Species that Support a Sustainable Riparian Habitat Annual Maintenance and Monitoring

42 Acknowledgements Gwinnett County Department of Water Resources The Dickerson Group CH2M HILL Staff

43 Questions?

44 Wetland and Buffer Planting Photographs

Joel Tillery, P.E., CH2M HILL. SESWA 2010 Annual Conference October 7, 2010

Joel Tillery, P.E., CH2M HILL. SESWA 2010 Annual Conference October 7, 2010 Joel Tillery, P.E., CH2M HILL SESWA 2010 Annual Conference October 7, 2010 The need for water quality improvement is a reason to play the game. Local governments dealt a variety of federal, state, and