Presentation at Massachusetts Sustainable Communities and Campuses Conference on March 17, 2017

1. Manchester-by-the-Sea
Comprehensive Watershed
Planning for Climate
Change
Sustainability by Land & Sea - 7th Massachusetts Sustainable
Communities & Campuses Conference
Endicott College
March 17, 2017
Janet Moonan, P.E., Project Manager

2. The Community

3. Sawmill Brook Watershed Concerns

8. Sawmill Brook Watershed Concerns
Inland Flooding
• Poor Soils
• Impervious Surface
• Channelized Drainage
Coastal Flooding
• High Tide
• Wave Action
• Storm Surge
Water Quality Issues
• Bacteria
• Low pH
• Sedimentation

9. Flooding Impacts Community Assets
People
Built
Environment
Economy
Natural
Environment

10. Town Hall &
Police
WWTP
Fire Station

11. Climate Change Adaptation-
Opportunities for Wastewater
Town Hall &
Police
WWTP
Fire Station

12. Future Flooding from Coastal Influences
http://www.geosciconsultants.com/projects/2015/5/27/coastal-risk-mapping-in-salem-sound

13. Big Picture View ...
Strategic Thinking
■ Town Staff wanted to understand future impacts
of climate change on the town, recognized
comprehensive approach needed.
■ Funding strategy included applying for CZM
Grants and FEMA Grants
■ Coordinated work between grants.
■ Included not only flood mitigation but habitat
improvement and water quality improvements
■ To reduce risk and vulnerability of flooding on
community assets, considered Green
Stormwater Infrastructure

14. Green Stormwater Infrastructure…
A lot of options to consider…
Roof Drain Disconnects & Rain Harvesting
Bioretention / Rain Gardens
Infiltration Practices
Constructed Wetlands
Street Planters
Porous Pavement
Pretreatment & Filters
Green Roofs
Stream Bank Storage

15. An “Easy” Seven-Step Process to Assess
Green Infrastructure
1. A desktop (GIS-based) screening and ranking;
2. Review of results and complete site visits;
3. Identify other site conditions that would impact
implementation;
4. Conceptual sizing of GSI practices (volume treated, pollutant
reduction, etc.);
5. A hydrologic and hydraulic model evaluation;
6. Calculation of pollutant load reduction; and
7. Development of costs … assess cost vs. benefit.

16. Desktop Assessment:
Primary Screening

17. Desktop Assessment:
Primary Screening

18. Desktop Assessment:
Primary Screening

19. Desktop Assessment:
Primary Screening

20. Desktop Assessment:
Primary Screening

21. Desktop Assessment:
Primary + Secondary Screening

22. Additional Considerations
Permitting and Environment
– Wetlands
– Drinking water impacts
– Habitat impacts
– Historical area
– Contamination
– Sea Level Rise
– Etc
Qualitative Input
– Community support
– Cultivation of educational opportunities
– Operation & Maintenance
– Aesthetic and habitat improvement
– Coordination with other town project
– Etc

23. Field Work to Assess Green Infrastructure
Assessment of:
■ Existing structures (23 culverts and tide gate)
■ Potential structural solutions (17 sites for Green
Infrastructure/ Flood Mitigation)

24. What we found…
Large parking areas at High School
Parking at Elementary School
Parking at Turf Field

25. What we found…
Small flood storage areas
Large flood storage areas

26. Defined extent of BMP corridors in Phase 2 Downtown Improvement areas
What we found…

27. Let the modeling show…
■ Incorporated stormwater
GSI into watershed-wide
HEC-RAS model
■ Looked at current and
future (2025, 2050, 2100)
Scenarios
■ Even for larger projects (i.e. golf course flood
storage, elementary school parking lot,) limited
potential to reduce watershed-wide surface water
elevations under all scenarios

28. Porous Asphalt Parking Area
at Coach Field

31. Manchester is moving forward in these
ways…
■ Updating Town Master Plan to identify climate
change risks, vulnerability to community assets
and mitigation solutions
■ Formalizing actions in an approved FEMA Hazard
Mitigation Plan, including GSI in downtown and to
address roadway flooding
■ Keeping the public informed and engaged through
public workshops, web site update and news
articles

32. Questions?
Gabrielle Belfit, Senior Environmental Scientist, Project Manager
– Phone: 508-564-7285
– Email: GCBelfit@TigheBond.com
Janet Moonan, P.E., Project Engineer
– Phone: 781-708-9826
– Email: JSMoonan@tighebond.com
Mary Reilly, Grants Administrator
– Phone: 978-525-6427
– Email: reillym@manchester.ma.us
Documents can be found the Manchester town website at:
www.manchester.ma.us/354/Sawmill-Brook-Watershed-Project
and
www.manchester.ma.us/355/FEMA-PDM-Grant-Projects