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

7.
Project Components
• Wetland Forebay; Water Quality Swale; Wetland
Basin; Oxbow/Floodplain; and Parkland

8.
Water Level Fluctuation Plan
– Drought Condition

9.
Water Level Fluctuation Plan
– Dry Weather “Baseline”

10.
Water Level Fluctuation Plan –
2-Year Storm

11.
Water Level Fluctuation Plan –
5-Year Storm

12.
Water Level Fluctuation Plan –
10-Year Storm

13.
Water Level Fluctuation Plan –
100-Year Storm

14.
Wetland Basin

15.
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

16.
Wetland Basin - Plant Selection
• Pollutant removal capacity
• Natural habitat community-based
• Native to SE Massachusetts (no
cultivars)
• Wildlife and cover value
• Commercially available

17.
Wetland Basin - Plantings

18.
Wetland Basin Plantings
• Over 120,000 wetland plugs
and tubers planted
• Habitats include open water,
deep marsh, emergent marsh,
high marsh, and wet meadow

19.
Wetland Basin

20.
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

21.
DCR Parkland – Upland Habitat
• Scrub/shrub, Riparian Woodland
(wet and dry) habitats
• All species native to SE
Massachusetts; no cultivars used

22.
Construction 2011-2013

23.
Establishment Period
Summer 2013

24.
Develop
O & M
Manual

25.
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

26.
Agency Responsibility Diagram

27.
Add break slide
Training Workshops

28.
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

29.
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

30.
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

31.
Water Quality
Sampling Stations
CambridgePark
Drive
Wetland
Outlet

32.
Post-Construction Activities –
Invasive Management

33.
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

34.
Vegetation Management Plan

35.
Inspection
Checklists