Doyle Park Reconstruction Project Improving Flood Control Facilities to Meet a TMDL

Transcription

1 Doyle Park Reconstruction Project Improving Flood Control Facilities to Meet a TMDL Ann Arbor, Michigan Washtenaw County Drain Commissioner & Malletts Creek Coordinating Committee November, 2007 Janis Bobrin - Washtenaw County Drain Commissioner Ed Kluitenberg, Mark TenBroek,, Jay Zawacki - CDM Michigan, Inc.

2 Presentation Overview Background Study/Design Construction Initial Performance Project Cost/Funding Future Activities

3 Background

4 Project Team Washtenaw County Drain Commissioner s Office MDEQ City of Ann Arbor Pittsfield Township Huron River Watershed Council Malletts Creek Association Consulting Team

5 Malletts Creek Watershed Doyle Park Regional Detention Basin

6 Existing Facility Designed for Flood Control NURP Sampling Removals TSS 35% Phos. 14%

7 Brown Park Recreational Uses Biking Walking Playground area Basketball Birding Sledding Disc golf

8 Malletts Creek Restoration Plan Plan completed in 2000 Relevant Goals: Reduce phosphorus pollution Control stream velocities and flow rates Increase habitat for fish and wildlife Change to Doyle Park was a keystone recommendation Installed Malletts Creek stream gage

9 Study/Design

10 Public Engagement Community workshops As-needed focus meetings Progress meetings w/ Malletts Creek Coordinating Committee Project web site

11 Refined Project Objectives Phosphorus Removal & Sediment Management (Meet TMDLs) Channel Integrity Habitat Diversity Public Health Protection Community Recreation and Educational Value Management and Maintenance Community Input/Education

12 Highly Variable Stream Flows

13 Malletts Creek Phosphorus Load Closely Related to Suspended Solids Load

14 Sampling / Monitoring of Existing Pond Temp. increases up to 14 deg F Zero TSS/Phos Phos.. removal Good aeration at outlet Strong diurnal DO - excess algae Dissolved Oxygen Concentration DO Conc. (mg/l) Upstream (BP1) Dow nstream (BP2) 8/27 8/28 8/29 8/30 8/31 9/1 9/2 9/3 9/4 9/5 9/6

15 Sediment Characterization Average depth of 5 ft 33,000 CY 8 sediment cores analyzed for 12 metals Some results above direct contact threshold WCDC elected off- site disposal

16 Floristic Quality Assessments Wetland Overflow Area Old Field Oak/Hickory Woodland

17 Delineation of Existing Wetlands

18 Existing/Future Detention Volumes Figure Brown Park Detention Basin Volumes (MG) Flood Control Only Extended Detention Permanent Pool Accumulated Sediment Volume (MG) As-Built (1979) Existing Conditions (2003) Concept 1 Shallow Pond Concept 2 Meandering Stream Concept 3 Terraced Pools Concept 4 Stream w/ Forebay Concept 5a Deep Wetland Concept 5b Medium Depth Wetland

19 Continuous Simulation of Alternatives with SWMM EXTRAN Model

20 Annual Avg. Capture of Wet Weather Flows Annual Average Capture of Wet Weather Flows Capture 100% 90% 80% 70% 60% 50% 40% 30% 20% 10% 72 hour drawdown 48 hour drawdown 24 hour drawdown Concept 1 - Shallow Pond (34%) Concept 2 - Meandering Stream (64%) Concept 3 - Terraced Pools (82%) Concept 4 - Stream w/ Forebay (68%) Concept 5a - Deep Wetland (87%) Concept 5b - Medium Depth Wetland (83%) 0% Extended Detention Storage Volume (MG)

21 Predicted Pollutant Removal Efficiency Figure 1-3: Predicted Removal Efficiency by Sedimentation Removal Efficiency 80% 70% 60% 50% 40% 30% 20% 10% Total Suspended Solids Total Phosphorus 0% Concept 1 Shallow Pond Concept 2 Meandering Stream Concept 3 Terraced Pools Concept 4 Stream w / Forebay Concept 5a Deep Wetland Concept 5b Medium Depth Wetland

22 Selected Design Forebay w/ diversion and access road Extended detention wetland Mitigation wetland Embankment dam Modified outlet Expected performance ~ 35% Phos.. removal ~ 60% TSS removal

23 Creating a New Public Amenity - Inviting Increased Use Integrated disc golf course Expanded water use/access Pedestrian bridge Looped pathway Native landscaping Mitigation wetland forbs and grasses, high diversity, habitat structures Detention wetland forbs and grasses, lower diversity due to inundation depths Shoreline/upland areas trees, shrubs, forbs, grasses

24 Construction

25 Doyle Park Construction Fall 2006

26 Downstream End - Temporary Diversion Channel

27 Sediment Removal/Drying

28 Upstream Weir Inlet to Forebay

29 Embankment Dam Construction

30 Doyle Park Construction August 2007

31 Outlet Structure Modifications

32 Extended Detention Wetland

33 Mitigation Wetland

34 Initial Performance

35 Embankment Dam Construction Detention Activated

36 Embankment Dam Overtopping August 20, 2007

37 Embankment Dam Overtopping August 20, 2007

38 Project Costs / Funding Construction Cost $2.54 Million $1.25 Million CMI Grant First SRF-financed NPS project in Michigan % User Costs allocated to Malletts Creek Drainage District City of Ann Arbor Pittsfield Township MDOT Washtenaw County

39 Future Activities Construction completion: Fall 2007 Wetland mitigation monitoring & reporting Observation of plantings Floristic Quality Assessment Water quality sampling to establish actual TSS and phosphorus removal Long-term operation and maintenance