MMS ENVIRONMENTAL STUDIES PROGRAM: ONGOING STUDIES
MMS OCS Region: Headquarters
Title: Analysis of Potential Biological and Physical Dredging Impacts on Offshore Ridge and Shoal Features/Engineering Alternatives and Options to Avoid Adverse Environmental Impacts (NT-03-06)
Total Cost:

$400K

 Period of Performance:

FY 2003-2006
Conducting Organization:

Continental Shelf Associates
MMS Contact:

Colleen Finnegan
Description:
Background
The submerged shoals located in Federal offshore the East and Gulf of Mexico coasts are being targeted as potential sources of sand for beach and coastal restoration projects. Some of these shoals have already been dredged and are being considered as a long-term source of material for beach replenishment efforts. However, these features are often areas of intense biological activity (fishery resources, etc.), as well as playing a role in mitigating the local wave climate, especially during intense storm events. The recently completed biological/physical monitoring protocols study (MMS OCS Study 2001-089) raised several questions relative to the continued use of submerged shoals as sand borrow areas:
 
  1. Are there procedures to dredge shoal and ridge features that will minimize ecological impacts and/or speed recovery, such as dredging completely one specific shoal or ridge and leave adjacent features un-touched vs. dredging a small amount of sand from each shoal or ridge feature, or dredging in strips leaving undisturbed areas that act as local sources of recruitment and allow recruitment from older life stages.
  2. Is there a preferred manner to remove sand from a shoal/ridge feature to maximize their use and maintain the integrity of the feature? For example, there are currently concerns that certain dredging practices results in the accumulation of fine-grained sediments in the burrow areas, making the site unsuitable for re-use. Also, there are questions about where on ridges is it best to dredge to speed recovery and reduce long-term impacts.
Objectives

The objectives of the study are to examine the biological and physical effects of offshore dredging within the ridge and swale features on the Federal OCS and to suggest engineering options and mitigation measures that can be implemented to avoid potential deleterious impacts.
Methods

The study involves data collection and numerical wave modeling within a ridge and swale feature (probably in the mid-Atlantic area) which has undergone dredging.  The data will be compared to an undredged area within the same system.  A dredging engineer will be an integral member of the technical team and will provide expertise relative to options that can be implemented to avoid adverse impacts while still allowing for the use of the shoal as a source of sand for beach nourishment projects.
Importance to MMS

The majority of the areas now being considered within federal waters as sand sources for beach and coastal restoration projects are submerged shoals.  This trend will continue into the forseeable future.  If the MMS is to regulate the use of these areas in an environmentally sound manner, it is imperative to have the information on hand that can be used to assess the continued use of these shoals.
Current Status: The study has been significantly delayed waiting on finalization of the Versar Maryland/Delaware finfish habitat study, the results of which are critical to this effort.
Final Report Due:

A new date for delivery of the final report will be discussed soon.
Publications:
Affiliated WWW Sites:  
Revised date:

February 2006
ESPIS

ESPIS - All completed ESP Studies:
Full Text, Online, Right Now!
 Environmental Studies Program Information System