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Study Title: Environmental Survey Of Potential Sand Resource Sites: 

Offshore New Jersey 

Report Title: Environmental Survey Of Potential Sand Resource Sites: 

Offshore New Jersey, Volume I: Main Text, Volume II: Appendices 

Contract Number: 14-35-01-97-CT-30864 

Sponsoring OCS Region: Headquarters – International Activities and Marine 

Minerals Division 

Applicable Planning Area(s): Offshore New Jersey 

Fiscal Year(s) of Project Funding: FY1997 to FY2000 

Completion Date of Report: December 2000 

Costs: FY 1997: $ 594; FY 1998: $136,427; FY 1999: $340,528; 

 FY 2000: $ 102,240; FY 2001: $ 19,265; Cumulative Costs: $599,054 

Project Manager: Mark R. Byrnes, Ph.D. 

Affiliation (Project Manager): Applied Coastal Research and Engineering, Inc. 

Address: 766 Falmouth Road, Suite A-1, Mashpee, MA 02649 (Applied Coastal) 

Principal Investigators: Mark R. Byrnes, Ph.D.; Richard M. Hammer, Ph.D. 

Key Words: sand resource, offshore New Jersey, currents, sediment transport, 

wave modeling, bathymetry change, dredging, benthic, pelagic, recolonization 

Background: The New Jersey Geological Survey characterized eight sand 

resource areas in Federal waters offshore New Jersey as potential borrow 

sites for beach nourishment. The main purpose of this study was to address 

environmental concerns associated with dredging sand from these Outer 

Continental Shelf (OCS) sites. 

Objectives: Provide MMS environmental information to assess the potential 

impacts of offshore dredging activities and to identify ways in which 

dredging operations can be conducted so as to minimize or preclude long-term 

adverse biological and physical impacts to the environment. Five primary 

study elements were developed for addressing environmental concerns 

associated with offshore sand dredging for beach replenishment. They 

included: 1) characterize benthic ecological conditions, using existing data 

sets and data collected from field work, in and around the proposed sand 

borrow sites; 2) evaluate benthic infauna present in the proposed sand 

resource areas, and assess the potential effects of offshore sand dredging on 

these organisms; 3) develop a schedule of best and worst times for offshore 

sand dredging in relation to transitory pelagic species; 4) evaluate 

potential modifications to waves due to offshore sand dredging within the 

proposed sand resource areas; and 5) evaluate the potential impact of 

offshore dredging and consequent beach replenishment on sediment transport 

patterns, sedimentary environments, and impacts to local shoreline processes. 

Description: The inshore portion of the continental shelf, seaward of the 

Federal-State OCS boundary and within the New Jersey Exclusive Economic Zone 

(EEZ), encompasses the project study area (Figure 1). The seaward limit of 

the study area is generally within about 20 km of the shoreline. Sand 

resource areas are located on the New Jersey OCS between the 10- and 20-m 

depth contours. The continental shelf surface within the study area contains 

many first-, second-, and third-order morphologic features formed during the 

Holocene transgression. Sand ridges 2- to 5-m high and 0.5- to 1.5-km apart 

represent second-order features that are the primary sand resource targets of 

this study. 

 Eight potential sand resource areas within the study region were evaluated 

to determine the potential impacts of offshore sand mining for beach 

replenishment. Areas A1, A2, G1, G2, G3, C1, and F2 contain borrow sites with 

the greatest potential for use in the future (Figure 1). Field surveys were 

conducted to characterize benthic infauna and epifauna at each resource area. 

In addition, existing physical processes and biological data were compiled 

and analyzed to assess the potential impacts of offshore dredging activities 

to minimize or preclude long-term adverse environmental impacts at potential 
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borrow sites. Furthermore, wave transformation and sediment transport 

numerical modeling were employed to simulate the physical environmental 

effects of proposed sand dredging operations offshore and along the coastline 

landward of resource areas to ensure that OCS sand resources are developed in 

an environmentally sound manner. 

Significant Conclusions: Potentially rapid and significant changes in 

bathymetry due to sand extraction from the OCS may have substantial impact on 

wave propagation patterns on the continental shelf and at the shoreline. As 

such, substantial effort was spent understanding existing wave propagation 

patterns relative to those resulting from potential sand extraction 

scenarios. For directional approach simulations, significant wave heights 

experience little variation up to the 20-m depth contour, where waves begin 

to be influenced of bathymetry. The region offshore Townsends and Corsons 

Inlets (Area A) has a relatively consistent longshore wave height 

distribution. Several areas of wave convergence and/or divergence were caused 

by shoals surrounding Areas A1 and A2. These features focus wave energy at 

various locations along the coast depending on the wave approach direction. 

The area to the south of Barnegat Inlet (Area C) also experiences a 

consistent wave height distribution along the shoreline. Shoals and 

depressions south of Area C1, as well as offshore linear ridges to the north, 

produce significant wave transformation within the modeling domain. Wave 

energy focused by these features most often impacts the Harvey Cedars and 

Loveladies regions. Offshore Little Egg and Brigantine Inlets (Area G), wave 

transformation again is controlled by numerous linear ridges. Increased wave 

heights appear most frequently near Brigantine Inlet. The area seaward of 

northern Barnegat Bay (Area F) also experiences wave height changes produced 

by offshore shoals and depressions within the modeling domain. Consistent 

wave focusing is observed by the shoal within Area F2, as well as the shoals 

to the south and southeast of F2. Wave energy focused by these features 

impacts regions from Seaside Park north to Bay Head, depending on approach 

direction. 

 Post-dredging model simulations were performed by numerically excavating 

proposed borrow sites for seven of the resource areas. Differences in wave 

height between pre- and post-dredging scenarios offshore New Jersey indicate 

maximum wave height increases for directional approach simulations ranging 

from 0.1 to 0.25 m (7 to 16% of the initial wave height). The magnitude of 

modifications increase as the magnitude of waves increase or when the 

orientation of potential borrow sites align with waves to produce maximum 

impact (e.g., southeast approach at Area A). In Areas A and G, which contain 

the southernmost borrow sites, maximum changes dissipate relatively quickly 

as waves advance towards the coast and break. In Areas C and F, maximum 

changes do not dissipate as readily. At potential impact areas along the 

coast, wave height changes average ±0.13 m, ±0.15 m, ±0.11 m, and ±0.10 m for 

Areas A, G, C, and F, respectively. These modifications represent changes of 

approximately ±3 to 15% when compared with wave heights for existing 

conditions. 

 Three independent sediment transport analyses were completed to evaluate 

impacts due to sand mining. They included quantifying historical sediment 

transport trends using historical bathymetry data sets; documenting sediment 

transport patterns at proposed offshore borrow sites using wave modeling 

results and current measurements; and modeling nearshore currents and 

sediment transport using wave modeling output to document potential impacts 

to the longshore sand transport system (beach erosion and accretion). 

Initially, sediment transport at borrow sites will experience rapid changes 

after sand dredging is complete. Sediment that replaces the dredged material 

will fluctuate based on location, time of dredging, and storm characteristics 

following dredging episodes. Average transport rates range from a minimum of 
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28 m3/day (about 10,000 m3/yr; Area F2) to a high of 450 m3/day (about 164,000 

m3

/yr; Area A1), while the infilling time varies between 54 (Area A1) to 303 

years (Area C1). For average annual conditions, mean longshore sand transport 

rates were approximately equal landward of proposed borrow sites. The 

absolute value of the mean difference between existing and post-dredging 

conditions was relatively consistent, ranging between 9,000 (20.0%) and 

14,900 m3

/yr (7.2%) along the New Jersey shoreline. Although the percent 

difference computed for the northern two grids (Areas C and F) was larger 

than that calculated farther south, this trend is a result of the low 

relative net transport rates along the northern beaches rather than an 

increase in impacts associated with dredging. 

 Results of the biological field surveys agreed well with previous 

descriptions of benthic assemblages residing in shallow waters off the New 

Jersey coast. Numerically dominant infaunal groups included numerous 

crustaceans, echinoderms, molluscans, and polychaetes, while epifaunal taxa 

consisted primarily of decapod crustaceans, sand dollars, moon snails, and 

squid. Potential benthic effects from dredging will result from sediment 

removal, suspension/dispersion, and deposition. They are expected to be 

short-term and localized. Temporal and recruitment patterns indicate that 

removal of sand between late fall and early spring would result in less 

stress on benthic populations. Atlantic surfclam is the most economically 

important benthic species found in or around the sand resource areas. Once an 

exact borrow site is chosen for dredging, a commercial clam fisher should be 

hired to evaluate the site for the presence and abundance of Atlantic 

surfclams. If commercial quantities are found, then the fisher should harvest 

them from the site prior to dredging. This approach would remove individuals 

that would be subject to impacts. Studies have demonstrated that juvenile 

Atlantic surfclams will recruit to dredged borrow sites. 

 Zooplankton, squids, fishes, sea turtles, and marine mammals were groups 

in the pelagic environment considered to be potentially affected by offshore 

dredging. No cumulative effects to any of these pelagic groups are expected 

from multiple sand mining operations offshore New Jersey. 

Study Results: Minimal physical environmental impacts due to potential sand 

dredging operations have been identified through wave and sediment transport 

simulations. However, under normal wave conditions, average change in 

longshore sand transport is about ±13% of existing conditions. Because wave 

and sediment transport predictions are only reliable to within about ±25%, 

predicted changes are not deemed significant. Although changes during storm 

conditions illustrate greater variation, the ability of models to predict 

storm wave transformation and resultant sediment transport is less certain. 

 The data collected, analyses performed, and simulations conducted indicate 

that proposed sand dredging at sites evaluated on the OCS offshore New Jersey 

should have minimal environmental impact on fluid and sediment dynamics and 

biological communities. Short-term impacts to benthic communities are 

expected due to the physical removal of borrow material, but the potential 

for significant cumulative benthic impacts is remote. No cumulative effects 

to any of the pelagic groups are expected from potential sand mining 

operations. 

Study Products: Byrnes, M.R., R.M. Hammer, B.A. Vittor, J.S. Ramsey, D.B. 

Snyder, J.D. Wood, K.F. Bosma, T.D. Thibaut, N.W. Phillips, 2000. 

Environmental Survey of Potential Sand Resource Sites: Offshore New Jersey. 

U.S. Department of the Interior, Minerals Management Service, International 

Activities and Marine Minerals Division (INTERMAR), Herndon, VA. OCS Report 

MMS 2000-052, Volume I: Main Text 380 pp. + Volume II: Appendices 291 pp. 

*

 P.I.’s affiliation may be different than that listed for Project Manager. 
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Figure 1. Location of New Jersey study area and potential sand resource sites.