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Townsends Inlet to Cape May Inlet Project

The Townsends Inlet to Cape May Inlet Coastal Storm Risk Management Project was authorized by Congress in 1999. The project includes the construction of a dune and berm system with a 3-year nourishment cycle (pending available funding) and 2.2 miles of seawall along the Townsends Inlet frontage of Avalon and the Hereford Inlet frontage of North Wildwood. The design calls for a 150 foot berm (or beach) backed by a dune constructed to elevation +14.75 (North American Vertical Datum of 1988). The beachfill portion of the project was initially constructed in 2002. The Townsends Inlet seawall was completed in 2006. The Hereford Inlet seawall was constructed in 2 phases with the Phase 1 completed in 2007 and Phase 2 completed in 2010. The dune and beachfill project was renourished/repaired in 2011, 2013, 2017, and 2019. The Hereford Seawall was repaired in 2014.

The project is designed to reduce the risk of damages to infrastructure from coastal storm events. 

The dune and beachfill portion of the Townsends Inlet to Cape May Inlet project was initially constructed in 2002 and has been subsequently renourished and repaired. The next scheduled periodic nourishment is scheduled for 2021 pending available funding. The Townsends Inlet seawall was completed in 2006. The Hereford Inlet seawall was constructed in 2 phases with the Phase 1 completed in 2007 and Phase 2 completed in 2010. In the summer of 2020, repair work is expected to begin along the Hereford Inlet (Anglesea) seawall. 

The project is designed to reduce the risk of damages to infrastructure from coastal storm events. 

Year

Activity

2002

Initial construction of dune and beachfill 

2009

Construction of Townsends Inlet and Hereford Inlet seawalls

2011

FCCE Emergency Repair

2013

FCCE Emergency Repair

2017

Periodic Nourishment

2019

 Periodic nourishment

2020

Hereford Inlet Seawall Repairs (ongoing)
2021

Periodic Nourishment (scheduled; pending funding)

Anglesea/North Wildwood Seawall Repairs

In cooperation with the New Jersey Department of Environmental Protection (NJDEP) and the City of North Wildwood, the U.S. Army Corps of Engineers (USACE) awarded a contract to Agate Construction to repair damage along sections of the Hereford Inlet Seawall.

Erosion along the underwater edge of the wall caused portions of the wall to collapse. To fix the problem, Agate will install concrete block mattresses that extend into the channel along the bottom of the inlet. The mattresses will then be covered with more than 20,000 ton of stone. The mattresses are designed to fold into areas of erosion and prevent the erosion from migrating towards the wall. Prior to Labor Day, all construction work will be from barges in the inlet. Concrete mattress and stone will be loaded on the barges from Staging Area #1 (see construction map on below tab). Following Labor Day, construction will begin from land based operations adjacent to the wall.

Continued erosion along the seawall between when USACE designed the seawall repairs and actual construction resulted in additional failure along the seawall. To address this issue, USACE expanded the contract with Agate, within the original scope of work, to add an additional 21,000 square feet of Articulated Concrete Block (ACB) mattresses, 5,000 tons of stone fill and 400 tons of 2-ton cap stone.

The seawall was originally constructed in 2009 and provides coastal flood risk management for homes along the Hereford Inlet. 

Continued erosion along the seawall between when USACE designed the seawall repairs and actual construction resulted in additional failure along the seawall. To address this issue, USACE expanded the contract with Agate, within the original scope of work, to add an additional 21,000 square feet of Articulated Concrete Block (ACB) mattresses, 5,000 tons of stone fill and 400 tons of 2-ton cap stone.

Planned Activities February 22 - March 31, 2021

Over the course of the next month, construction will begin to transition from water based operations into a combination of water and land based construction. Agate will finish the base construction of the wall in Repair Area 2 by the end of February and begin construction of the 2-ton cap stone in this area. The cap stone work will be built from the land. This will mean an increase in truck and heavy equipment traffic within the project site.

Simultaneous with the cap stone work in Repair Area 2, Agate will begin construction of the base wall repairs in Repair Area 1. This will include the placement of the Articulated Concrete Block (ACB) mattresses and stone fill the same as was done in Repair Area 2.

Work on Repair Area 3 has not been determined at this time.

Safety of our workers and the public is our primary concern.  Construction sites are full of hazards that workers are trained and outfitted to handle. Please help us keep you and our workers safe by following all caution signs, staying clear of heavy equipment and large vehicles, and not letting curiosity bring you inside our secured work area. Be aware of increased truck traffic, construction noise and other hazards that present themselves around the construction area. Your awareness and vigilance help us ensure ZERO accidents.

Structure and Vibration Monitoring

Construction activities such as moving large equipment and stone placement can cause the ground to shake. If the shaking or vibrations are large enough, they can cause damage to nearby structures. To avoid this, the Seawall Repair contract requires that the contractor monitor their activity in order to predict and prevent damages to structures as a result of their work. The contractor does this by strategically placing seismographs around the project site where large and/or heavy equipment are operating. The seismographs are placed to capture the highest peak particle velocity created by the construction activity and record continuously using threshold-type and fully automated seismographs. Because the magnitude of vibrations decrease as the distance from the source increases, monitors are not required in all buildings as alerts are set to trigger at thresholds below the damage limits at the monitored location.

An alert warning is given to the contractor and USACE personnel if any measured vibration exceeds 0.60 inches per second (IPS) or 80% of the allowable limits established by the U.S. Bureau of Mines (USBM RI 8507). If an alert is issued, all work will stop until remedial measures and/or modified construction procedures are identified.

It takes a substantial amount of vibration to cause damage to surface structures, underground structures, pipelines, sewers and water wells. Surface structures, underground facilities and wells are dynamic in nature and as such are subject to a variety of internal and external forces such as settlement, weather and changes in soil moisture, excavation, and frost levels.

The U.S. Bureau of Mines Report of Investigations 8507, “Structure Response and Damage Produced by Ground Vibration from Surface Mine Blasting (USBM RI 8507) reported the following findings:

  • Threshold damage, defined as opening of old cracks, formation of new hairline cracks in drywall or plaster wall finishes, and dislodging of loose objects, typically appeared at approximately 2 to 3 IPS and was never observed at less than 0.5 IPS.
  • Minor damage, such as broken windows, loosened or fallen plaster, and hairline cracking of masonry, typically appeared at approximately 4 to 5 IPS and was never observed below 1.0 IPS.
  • Major structural damage, such as wide cracking or shifting of foundations or bearing walls, typically did not occur until levels well above 5 IPS.

Ground-borne vibration is not a phenomenon that most people experience every day. Human response to vibration in buildings is very complex. The degree of annoyance cannot always be explained by the magnitude of the vibration alone. In some cases, the complaints are associated with measured vibration that is lower than the perception threshold. Other phenomena such as ground-borne noise, rattling, visual effects such as movement of hanging objects, and time of day all play some role in the response of individuals.

Response Level

Velocity (IPS)

Perceptible

0.04

Troublesome

0.20

Severe

0.70

 

Dune System Animation During Potential Storm Event

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USACE Philadelphia District
100 Penn Square E.
Philadelphia, PA 19107
215-656-6515  
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