baxter road feasibility assessment & solutions
TRANSCRIPT
Baxter Road Feasibility Assessment & Solutions
Project Update
July 14, 2021
Agenda
© Arcadis 2020
Introductions1
Alternatives Overview
2 Where We Are
3
What We’ve Heard 4
Where We Are Going5
Our Team
© Arcadis 2020
Jennifer Lachmayr, PE, BCEE
Principal In Charge / Project Director
Kathryn Edwards, PE
Principal Engineer / Project Manager
Keren Bolter, PhD
Senior Resilience Planner
Irene Watts, PhD
Senior Coastal Modeler
Ryan Brong, EIT
Water Resources Engineer
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Project MissionThe Baxter Road Long Term Planning Project will create a community-supported actionable roadmap to implementation of short- and long-term solutions for the Baxter Rd area that help the community respond to rising seas and eroding coastlines through adaptation practices such as protection, accommodation, shoreline realignment, or no action.
Goal - to compare alternatives and develop a concept plan for moving forward based on analysis and community engagement
Challenge – finding a solution that is supported throughout the community.
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Project Name
Baxter Road Neighborhood Adaptation Plan
Also popular:
Baxter Road Long-term Planning
Future of Sconset Bluff and Beach
Where We Are
Project Updates
2021
TASKS February March April May June July August Sep.
Notice to Proceed / Kickoff
Task 1 – Review of Existing Information
Task 2 – Stakeholder Engagement *
Task 3 – Alternatives and Engineering Feasibility Analysis
Task 4 – Final Memorandum
Deliverable
Meetings
* Meetings assumed to be virtual
NTP
Kickoff
Project Schedule
We are here
Baxter Road Engineering Feasibility Assessment
8
1. Review of Existing Information (>500 documents) (complete)
2. Stakeholder Engagement (partially complete)
3. Alternatives / Feasibility Analysis (partially complete)
4. Summary of Findings & Recommendations (initiating)
7/14/2021
Stakeholder Engagement
Second Round of Focus Groups
ORANGE DARK RED
– Select Board
– Town Manager
– Town Departments
– CRAC
TOWN
Greenhills
The ‘Sconset Trust
Overview of Risk
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• Analysis is largely statistical in nature and is most appropriate for longer term look
• Did not include any shoreline protection in analysis
• Used variety of data sources including historic surveys (T sheets) and Lidar data 1846 - 2010
FEMA EROSION PROJECTIONS
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Tax Implications
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Estimated from 2013 taxes
$0
$20,000
$40,000
$60,000
$80,000
$100,000
$120,000
$140,000
$160,000
2030 2050 2100
Property Taxes for Affected Properties (FY12)
Quantifying Loss of Homes
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Building & Content Replacement
Estimated based on various factors – order of magnitude
Homes only – no utilities, no land
$-
$10,000,000
$20,000,000
$30,000,000
$40,000,000
$50,000,000
$60,000,000
$70,000,000
$80,000,000
$90,000,000
$100,000,000
2030 2050 2100
Total Value Lost
Alternatives Overview
Project Updates
Alternatives Overview
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Alternative Name Description Coastal Process
No Change in existing system and O&M Activities
Baseline Current
Adaptive dune nourishment with existing system
Incorporate an adaptive management approach to the sediment placed on the dune
Optimize placement volumes to variations in erosion and accretion to the template
Expand existing system As previously designed Greater alongshore distance protected
Removal, retreat and Baxter Road relocation
Relocate/abandon utilities and access to homes and lighthouse
Return to pre-construction conditions
Nearshore breakwaters with existing system
Add nearshore breakwater structures seaward of existing project
Add a wave attenuation component to reduce sediment movement in the lee side of the structure
No Action Remove system and no additional activities
Current
Approach to the Selection of Alternatives
• The alternatives analysis was performed from an engineering and coastal process perspective
• Bluff protection cannot be achieved without toe stabilization, so alternatives that provide bluff protection include toe stabilization.
• We explored other forms of innovative protection methods but some would not provide toe stabilization. – Nantucket is unique
• Removal of the current system and replacement with another form of toe stabilization would also have environmental and cost impacts.
• With these considerations, analysis was completed with the existing system in place for most alternatives, with a single variable changing each time.
Criteria for Assessment of Alternatives
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• Definition of purpose – what is the alternative intended to do?
• Service life – for what period of time would the alternative be effective in preventing significant bluff erosion.
• Initial construction cost – order of magnitude estimates for comparison between alternatives.
• Operations and maintenance – costs and other considerations; order of magnitude to compare between alternatives.
• Constructability – identify likely issues which could impact the ability to implement the alternative.
• Other feasibility issues – will vary with alternative but items may include supply (for sand); need for land acquisition; access; emergency services; adjacent impacts; etc.
• Environmental considerations – Impacts to endangered species, vegetation, habitat, etc.
Alternatives Selection Methodology
1
Storm Return PeriodMore Frequent Storms,
Lower Intensity
Infrequent Storms, Higher Intensity,
Jute, Coconut Fiber SeawallGeotube
Image Citations:1: MA, 2017, Applying the Massachusetts Coastal Wetland Regulations2: https://climateactiontool.org/content/restore-natural-coastal-buffers-beach-and-dune-nourishment-and-restoration3: http://sconsetbeach.org/wp-content/gallery/geotubes/GeoInstallation_Construction-4.jpg4: Field Photos, Newport, RI, 20125: Field Photos, Revere, MA 2011
NourishmentStone
Revetment
2 3 4 5
Toe Stabilization Alternatives and Storm Return Period
What We’ve Heard
Project Updates
What We’ve Heard & Current Tensions
Desire for consideration of soft erosion control installations.
Need for an island wide sediment transport study
Desire to understand feasibility of the nearshore breakwaters option a bit more.
Need to understand the tax implications better.
Consider combinations of adaptation pathways (e.g. begin building new access while also protecting bluff for some period of time)
What would the cost of a buyout program be?
Where We Are Going
Project Updates
Adaptation Pathways
Source: Werners, Saskia E., et al. "Adaptation pathways: A review of approaches and a learning framework." Environmental Science & Policy 116 (2021): 266-275. View HERE
21009.7ft
20706.1ft
20504.3ft
1. No Change in existing system and O&M Activities
2. Adaptive dune nourishment with existing system (and focus on access)
3. Expand existing system
4. Removal, retreat and Baxter Road relocation
5. Nearshore breakwaters with existing system
Present
20303.0ft
20211.5ft
Example PathwayTipping Point Due to:
• Sediment Availability
• Extreme Erosion Event
• Bluff within 25 ft of Rd
(~2023 Permitting time)
Implement Adaptation
Upcoming Activities
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Refined Alternatives Analysis
July
Stakeholder Meetings
August
Summary of Findings (Draft 9/9/21)
September
Arcadis. Improving quality of life.
© Arcadis 2020
Jennifer Kelly Lachmayr, PE, BCEE
Principal in Charge / Project Director
Thank You
Kathryn Edwards, PE
Principal Engineer / Project Manager
https://www.bostonglobe.com/metro/2014/09/28/battle-over-bluff-nantucket/L41admApMtz3ZGqsO8XlTI/story.html