duke bitsko - alewife stormwater wetland

Alewife Stormwater WetlandCambridge, MA

Carbon Farming to Reverse Global WarmingDuke Bitsko, Director of Interdisciplinary Design

3 May 2015

Presentation Outline1. Project Overview

2. Native Habitat Planting Strategies

3. Vegetation Management Strategies

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

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

Recreational Benefits

Educational Benefits

Project Components• Wetland Forebay; Water Quality Swale; Wetland

Basin; Oxbow/Floodplain; and Parkland

Water Level Fluctuation Plan – Drought Condition

Water Level Fluctuation Plan – Dry Weather

“Baseline”

Water Level Fluctuation Plan – 2-Year Storm

Wetland Basin

Plant CommunitiesVegetative 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

Wetland Basin - Plant Selection

• Pollutant removal capacity

• Natural habitat community-based

• Native to SE Massachusetts (no cultivars)

• Wildlife and cover value

• Commercially available

Wetland Basin - Plantings

Wetland Basin Plantings

• Over 120,000 wetland plugs and tubers planted

• Habitats include open water, deep marsh, emergent marsh, high marsh, and wet meadow

Wetland Basin

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

DCR Parkland – Upland Habitat

• Scrub/shrub, Riparian Woodland (wet and dry) habitats

• All species native to SE Massachusetts; no cultivars used

Construction 2011-2013

Establishment Period Summer 2013

Develop O & M

Manual

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

Agency Responsibility Diagram

Add break slide

Training Workshops

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

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

Water Quality Improvement• For the 1-month and 3-month storm

event - projected water quality enhancements:

1-month 3-monthContaminant 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

Water QualitySampling Stations

CambridgeParkDrive

WetlandOutlet

Post-Construction Activities – Invasive Management

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

Vegetation Management Plan

Inspection

Checklists

duke bitsko - alewife stormwater wetland

Environment