Duke Bitsko, landscape architect with Chester Engineers describes a large-scale project he worked on in the Alewife Reservation, transforming a degraded low-quality upland habitat into a constructed stormwater wetland and park. The interdisciplinary team incorporated green infrastructure strategies to create diverse upland and wetland native plant communities. Presented at the Urban and Suburban Carbon Farming to Reverse Global Warming conference at Harvard University on May 3, 2015, organized by Biodiversity for a Livable Climate. www.bio4climate.org

1. Alewife Stormwater Wetland
Cambridge, MA
Carbon Farming to Reverse Global Warming
Duke Bitsko, Director of Interdisciplinary Design
3 May 2015

2. Presentation Outline
1. Project Overview
2. Native Habitat Planting
Strategies
3. Vegetation Management
Strategies

3. CSO Compliance
Project –
Cambridge MA
• Federal mandate to clean
Boston Harbor
• Reduces CSO’s by 84% or
43.6 million gallons
annually to Mystic River
• Green Infrastructure
includes downspout
disconnect, porous paving,
bioretention and
constructed wetlands

4. Alewife Stormwater Wetland
• Largest stormwater wetland in Northeast
(3.5 acres/10.3 acre-feet)
• Cleans, stores, reduces and releases
stormwater to impaired stream system
• Integrates recreation, education and
ecology
• Commitment to long-term management
and monitoring
• State and City partnership

5. Recreational Benefits

6. Educational Benefits

8. Project Components
• Wetland Forebay; Water Quality Swale; Wetland
Basin; Oxbow/Floodplain; and Parkland

9. Water Level Fluctuation Plan
– Drought Condition

10. Water Level Fluctuation Plan
– Dry Weather “Baseline”

11. Water Level Fluctuation Plan –
2-Year Storm

12. Water Level Fluctuation Plan –
5-Year Storm

13. Water Level Fluctuation Plan –
10-Year Storm

14. Water Level Fluctuation Plan –
100-Year Storm

15. Wetland Basin

16. Plant Communities
Vegetative Zones
• Permanent Pool 3’ – 5.5’ deep
• Deep Marsh 18” - 3’ deep
• Emergent Marsh: 6” - 1’ deep
• High Marsh: 0 – 6” deep
• Wet Meadow: Ephemeral, infrequent inundation
• Upland Riparian: slopes and islands

17. Wetland Basin - Plant Selection
• Pollutant removal capacity
• Natural habitat community-based
• Native to SE Massachusetts (no
cultivars)
• Wildlife and cover value
• Commercially available

18. Wetland Basin - Plantings

19. Wetland Basin Plantings
• Over 120,000 wetland plugs
and tubers planted
• Habitats include open water,
deep marsh, emergent marsh,
high marsh, and wet meadow

20. Wetland Basin

21. Oxbow and Floodplain
 Compensatory flood storage and increased habitat diversity
 Flap gate and flow connection to Wetland Basin
 Open water habitat harbors alewife species
 Spillway overflow and storage

22. DCR Parkland – Upland Habitat
• Scrub/shrub, Riparian Woodland
(wet and dry) habitats
• All species native to SE
Massachusetts; no cultivars used

23. Construction 2011-2013

24. Establishment Period
Summer 2013

25. Develop
O & M
Manual

26. City of Cambridge:
• Outfall/inlet structures
• Forebay/WQ swale
• Wetland Basin
• WQ testing (TP, N, coliform)
MA DCR:
• Paths and boardwalks
• Amphitheatre and signage
• Non-wetland plantings
Operation and Maintenance
Responsibilities

27. Agency Responsibility Diagram

28. Add break slide
Training Workshops

29. Vegetative Zones
• Permanent Pool 3’ – 5.5’ deep
• Deep Marsh: 18” - 3’ deep
• Emergent Marsh: 6” - 1’ deep
• High Marsh: 0 – 6” deep
• Wet Meadow: Ephemeral, infrequent inundation
• Upland Riparian: slopes and islands
Stormwater Wetland –
Deep Pool Sediment Removal

30. Deep Pool Sediment Removal –
2 Step Process
1. Inspection:
• Kayak and measuring
stick (hard clay
bottom)
2. Sediment Removal:
• Drought conditions
(July -September)
• Vacuum truck hose
extension (from kayak)
and/or manual removal

31. Water Quality Improvement
• For the 1-month and 3-month storm event -
projected water quality enhancements:
1-month 3-month
Contaminant Expected Removal Rate
Total Suspended Solids 65% 75%
Lead 75% 80%
Zinc 40% 40%
Total Phosphorus 40% 40%
Total Nitrogen 25% 30%
Source: Schueler 1992

32. Water Quality
Sampling Stations
CambridgePark
Drive
Wetland
Outlet

33. Post-Construction Activities –
Invasive Management

34. Vegetation Management Plan
Components
• Qualification of Wetland Scientist
• Statement of VMP Goals
• Description of Target Vegetation
• Vegetation Inventory
• Methods of Control/Seasonal Schedule
• Regulatory Compliance

35. Vegetation Management Plan

36. Inspection
Checklists