Nearshore and Shoreline

Confidential Offshore Wind Cable Landfall Project

gzadan — Thu, 07 Oct 2021 13:48:51 +0000

Confidential Offshore Wind Cable Landfall Project gzadan Thu, 10/07/2021 - 09:48

Challenge

Geotechnical investigations were needed for preliminary design of the horizontal directional drilling (HDD) necessary to connect the offshore cable to an onshore vault. Utmost attention to detail was needed in order to support the project team’s commitment to making the high-profile offshore wind project a benefit to the community and stakeholders.

Solution

Energy generated by the turbines would be transmitted by multiple submarine transmission cables that would make landfall at one of two potential landfall sites. The submarine cable landfall is the critical link connecting the offshore submarine cable to the onshore electrical vault before continuing to the onshore interconnection substation further inland. GZA led a subsurface investigation program consisting of 100-foot-deep geotechnical test borings and an extensive geotechnical and thermal resistivity laboratory testing program. The work entailed classification of the subsurface conditions, in support of the HDD cable landing and associated support of excavations. GZA interpretated subsurface conditions and potential obstructions that could impede the HDD process. The work was completed in a compressed time schedule during the winter months, to reduce the impact on seasonal tourism. Coordination with local officials for protection of natural resources and for the health and safety of the public were paid the utmost attention.

Benefit

The project was completed on time and on budget and with a positive impression of the project team for the public.

High profile project with significant public participation
Comprehensive geotechnical investigation with deep test borings and extensive geotechnical and thermal resistivity testing suites
Highly visual coastal test boring setup with busy pedestrian and vehicle traffic
Utmost attention paid to coordination with local officials, protection of natural resources, health and safety, and coordination with the public

Energy

Hepburn Family Preserve Living Shorelines Case Study Briefing

gzadan — Tue, 31 Aug 2021 15:46:27 +0000

Hepburn Family Preserve Living Shorelines Case Study Briefing gzadan Tue, 08/31/2021 - 11:46

Challenge

Beach and dune erosion have been an ongoing issue along the approximately 450 linear foot barrier spit that makes up the Hepburn Dune section of the Old Saybrook shoreline. The Borough of Fenwick and Lynde Point Land Trust had expended significant effort and cost to stabilize the shoreline and Lynde Point Marsh during the last 10 to 15 years. Crab Creek, located landward of the dune, was blocked by sediment and the Connecticut Department of Energy and Environmental Protection (DEEP) had made emergency repairs. Shoreline erosion continued and in 2017 there was concern that future storm events may cause a breach of the barrier spit. A breach would have negative consequences for both improved property in the area and the recently restored Lynde Point Marsh and Crab Creek located upland of the barrier spit. GZA was retained in August 2017 by the Borough of Fenwick and Lynde Point Land Trust to design a solution.

Solution

GZA proposed designing a Living Shoreline approach to mitigate ongoing erosion and reduce the potential for a breach of the barrier spit. Additional funding was necessary to complete the design process and CIRCA awarded Fenwick a Municipal Resilience Grant. Several alternatives were developed and evaluated relative to system performance, likelihood of permit acceptance and cost. GZA evaluated the performance of the Living Shoreline under prevailing wind, tide, and wave conditions (to establish requirements for new wetlands survivability) and under storm conditions (storm surge and waves) representing different recurrence intervals. The recommended alternative utilizes: 1) a nearshore wetland sill to attenuate prevailing wave heights; 2) new fill and tidal wetlands between the sill and the beach; 3) reshaping of cobble beach; and 4) dune restoration with a quarrystone-reinforced, planted dune (above the Coastal Jurisdiction Line).

Benefit

A Living Shoreline provides the benefit of a nature-based approach to shoreline stabilization, consistent with the existing barrier spit and marsh setting and with only temporary habitat impact. This approach also addresses the erosive effects of existing, historical coastal structures located near the site. GZA assisted the Borough with an application for a CIRCA Municipal Resilience Grant which was awarded. The project was designated by DEEP as a pilot demonstration project with long term performance monitoring. GZA collaborated with CIRCA and the University of Connecticut to establish empirical Living Shoreline performance criteria applicable to Long Island Sound. The project was also recently presented by CIRCA as part of a Living Shoreline permit workshop.

Project Design

GZA is at the forefront of Living Shoreline and hybrid system design for coastal shoreline stabilization. GZA’s approach has been to integrate ecology and coastal engineering technologies to develop a rational method for design of Living Shorelines, and utilizes:

Detailed statistical analysis of wind, water level and wave data;
Assessment of the environmental stress conditions required for new marsh survivability (based on tidal elevation and prevailing wave height and frequency);
Use of high-resolution numerical wave and surge modeling;
Risk-based design which evaluates the system response under a range of conditions (from prevailing conditions to different recurrence interval coastal flood conditions), and;
Consideration of the state and local regulatory agency goals for living shorelines during design.

GZA used a very high resolution, 2-dimensional numerical wave model (SWAN) to characterize nearshore waves. The results of the wave modeling were used to: 1) determine the need for wave attenuation (for new marsh survivability); and 2) inform placement of the Living Shoreline features (e.g., wetlands and rock sills) to conform to the existing shoreline geomorphology and tidal and wave currents. This design approach enhances shoreline stabilization while avoiding significant habitat impact and creating additional erosion in the vicinity.

GZA’s SWAN modeling results of the prevailing wave conditions confirmed that the prevailing wave heights exceed marsh survivability criteria and new wetland sills will be required for wave attenuation. The project is on the southern facing shoreline, with a long fetch across Long Island Sound. GZA’s risk analysis established a probability-based design basis, which defines the performance of the system in terms of likelihood of failure and predicted frequency of maintenance.

GZA completed the permitting in one year. Construction began in 2020 and was completed on May 15, 2021.

CIRCA Municipal Resilience Grant application and award
Living Shoreline proposed for stabilization of barrier spit
State DEEP pilot demonstration project
Historical shoreline change assessment
Metocean data analysis
Numerical wave modeling
Numerical cross-shore sediment transport modeling
Living shoreline design, permitting and construction monitoring
Project Partners: Lynde Point Land Trust, Borough of Fenwick, CIRCA, Connecticut River Conservancy, Sea Grant Connecticut, State of Connecticut DEEP, SumCo Eco-Contracting (construction) and several individual and philanthropic funding partners
Connecticut Green Building Council 2022 Green Building Awards- Resilience Award of Honor

Waterfront and Coastal Engineering

Flood Hardening Program, Confidential Utility

Anonymous — ��Ϸ��d, 25 Sep 2019 16:58:55 +0000

Flood Hardening Program, Confidential Utility Anonymous ��Ϸ��d, 09/25/2019 - 12:58

Challenge

Electric substation facilities are among the most critical elements to our nation’s power infrastructure. Recent flood impacts and forecasts of more frequent severe weather events prompted one long-standing major utility client to request GZA’s assistance in creating a Flood Hardening Program to improve the flood resiliency of 50+ existing inland and coastal facilities in four states.

Solution

GZA’s comprehensive services spanned from program development to implementation and operation. Our scientists and engineers started with tracking Flood Insurance Rate Maps (FIRM) and relevant map amendments and revisions; reviewed current and archived facility plans; performed site visits with key stakeholders; researched flooding history; and completed a frequency / damage flood risk analysis for each site. At locations where a FIRM was not available or did not appear to represent current topography or flood risk, GZA performed hydraulic, and coastal hydrologic analyses to determine the 100-year (Base Flood Elevation) and 500-year flood elevation to assess potential impacts of flood barriers to facilities and floodways and submitted Letters of Map Amendments / Revisions to FEMA. After completing the research and analyses, GZA prioritized site needs and developed concepts and designs for flood hardening measures that fell into three general categories:

Long-term (permanent) flood hardening measures provide longer service life, require little or no storm response, and incorporate flood hardening into the substation design for optimal operations and maintenance (O&M). This approach requires the longest lead time for planning, design, permitting, and construction, and typically incurs the largest capital cost. GZA conducted detailed analysis of multiple civil design hardening alternative concepts, including one or more concepts involving installing a barrier system, raising select components, re-building at a higher elevation, or a combination. The analyses included estimated capital and design life costs, project durations, and associated risks and opportunities for each concept, followed with a ranking system to assist with the Client’s selection process.

Long-term measures have been implemented at several substations, and are planned for several more. Short-term flood hardening measures have been implemented at those substations where permanent hardening measures require long-term planning, design and construction.

Short-term (temporary) flood hardening measures have been implemented at eight substations, and are planned at three more. The short-term hardening is completed at those substations in order of highest to lowest priority in terms of flood risk and damage potential. Short-term flood hardening measures are designed with a three- to 10-year service life, and effectively reduce flood risk and damage potential until long-term measures are completed. GZA has provided support from planning through construction and operations. These temporary engineering solutions are barrier, sealing, and pumping systems designed to reduce the need for emergency manpower and equipment response prior to, and during storm events, and recovery efforts after storm events.

Interim measures are rapid-deployment barrier and pump systems established early in the flood program to protect the most critical substation components from flooding events before either the long-term or short-term hardening measures are in-place. Interim measures are portable barrier and pumping systems designed to be implemented with minimal heavy equipment and little to no site preparation or excavation. Implementation of the interim measures are more heavily reliant on manpower response. Training exercises, including mock-ups of various flood barrier systems, provided realistic guidance to assist in selecting the appropriate barrier and pump systems for each substation, and in allocating the necessary manpower and equipment resources to effectively implement the interim measures in the event of a forecasted flood event.

For each of the measures, GZA continues to interface with the client’s key stake holders including regulators, material vendors, permitting consultants, external contractors, and the client’s civil and electrical engineering, project management, O&M, construction, material staging, legal, environmental, procurement, and executive teams. Key stakeholder input, along with a solid leadership team, and GZA’s multi-disciplined design group effectively navigated the evaluation, permitting, design, construction, and implementation of all three categories of flood hardening measures. GZA’s follow-up services include engineering services during construction, as-built documentation, Activation and O&M Plans, and supporting the Client with training, storm forecasting, emergency response, and O&M. GZA also continuously re-evaluates flood risk and damage to reflect on-going substation improvements, FEMA’s FIRM updates, and updates in policy, regulation, and industry practice pertaining to future risk associated with climate change.

Benefit

GZA’s experience in flood hazard mitigation, civil engineering, and permitting support for power sector clients, as well as the firm’s keen knowledge of the regulatory environment in the client’s service territory, allowed work to proceed expeditiously. This utility’s existing and future substations will now be significantly more resilient, and their customers far less likely to experience outages or prolonged service restoration due to flooding.

Insights

Assessed Flood Vulnerability of 50+ Electrical Substations in Four States
Intensive Involvement with the Community, Industry and Regulators
Flood Risk Analyses, FEMA FIRM Letter of Map Amendments / Revisions
Long-Term, Short-Term, and Interim Flood Hardening Measures
Programming, Planning, Permitting, Design, Pre-Construction, Construction, and O&M Services
Storm Forecasting, Readiness and Response Support

Energy

Water

Transportation & Infrastructure

Natural Hazard Risk Management, Climate Adaptation and Resilience

Land Use and Environmental Planning

Construction Management

Long Wharf Flood Protection Study and Living Shoreline Design

Anonymous — Mon, 23 Sep 2019 14:07:14 +0000

Long Wharf Flood Protection Study and Living Shoreline Design Anonymous Mon, 09/23/2019 - 10:07

Challenge

The Long Wharf area of New Haven, located within FEMA VE and AE high risk flood hazard zones, is highly vulnerable to coastal flooding. It has historically experienced severe flooding and flood damage from hurricanes and extreme weather events dating to the Hurricane of 1938 and more recently during Hurricane Irene and Superstorm Sandy. Improved resilience to coastal flooding is imperative to the social, economic and ecological resilience of the City of New Haven and the region.

Solution

GZA implemented a flood protection study in the Long Wharf District of New Haven. The District consists of two distinct areas in their character and use: the waterfront shoreline and the industrial district. The Long Wharf Flood Protection Study included planning and design of coastal flooding mitigation and shoreline protection measures for the area located northwest of the Long Wharf shoreline to Union Avenue. An inter-disciplinary team led by GZA completed a detailed flood vulnerability analysis in the project area. Based on the results of the vulnerability analysis, the team identified flood control strategies that not only addressed economic concerns related to business disruption after flooding but also identified ways in which the flood mitigation alternatives benefit the general public by creating a visionary plan for the City to improve social, economic, and ecological resilience to sea level rise, local intense precipitation, storm surge, and erosion. GZA’s project team includes Utile, Biohabitats, and Cambridge Systematics.

GZA’s project approach was multidisciplinary, and the team:

Incorporated industry-accepted science for sea level rise and coastal flooding;
Performed statistical analysis on historical storm surge flood level data from relevant water level stations, such as those from National Oceanic and Atmospheric Administration (NOAA);
Used high resolution terrain data (post-Sandy);
Completed high resolution, hydrodynamic computer flood modeling to characterize coastal flooding and its effect on structures and natural features;
Created scenario-based flood maps to evaluate the vulnerability of the area to tides and storm surges;
Managed all information using Esri ArcGIS geographic information system (GIS) software;
Used a “risk-based�� approach, defining coastal flood hazards in terms of probability, consistent with methods currently being used by state and federal agencies; and
Identified resiliency strategies and alternatives that are consistent with City of New Haven’s current vision and plans for development.

The design includes an integrated approach to flood protection, shore protection, and environmental and ecological benefits, including a seawall, a buried revetment, timber walkway, beach nourishment and wetland enhancement, tidal flats, and oyster reef submerged breakwaters. This plan also creates a new level of access and usability of the shoreline by the public.

Benefit

The study identified strategies relevant to the character of the neighborhoods and areas to reduce coastal flooding in the district. It is also used as a road map for the City for creating social, economic, and ecological resilience in relation to future sea level rise impacts, storm surge, and erosion.

GZA’s permit-level design for the proposed Long Wharf Flood and Shoreline Protection project enables the City of New Haven to move forward quickly with final design and construction as funding is secured. The comprehensive analysis and design acknowledges that a resilient New Haven is critical to Connecticut and creates the resiliency features necessary to foster social, economic, and ecological health of the area.

Insights

US HUD CDBG-Disaster Recovery Grant
FEMA Building Resilient Infrastructure and Communities (BRIC) Grant
Review of Existing Plans
Vulnerability and Risk Assessment
Adaptation Options Analysis
Stakeholder Identification and Engagement
Public Information Meetings
Living Shoreline Design
Feasibility Analysis of Flood Mitigation Strategies

Connecticut

Water

Government

Waterfront and Coastal Engineering

Natural Hazard Risk Management, Climate Adaptation and Resilience

Land Use and Environmental Planning

Natural Resources and Ecological Services

Data Management, Analytics and Visualization Solutions