Benthic Studies

Benthic Studies for Pearl Harbor, HI, USA

During a Navy Region Hawaii construction dredging project to improve access to the Pearl Harbor channel, Cardno provided cutting-edge technology and expertise to help safeguard and improve the marine environment.

Navy Region Hawaii was considering a construction dredging project to improve the entrance to the Pearl Harbor channel and accommodate the Navy’s largest military vessels. To maintain compliance with the Endangered Species Act (ESA), Marine Mammal Protection Act (MMPA), and Magnuson-Stevens Fishery Conservation and Management Act (MSFCMA), the Navy was required to use the best available science to conduct an Environmental Assessment (EA) of the potential impacts of the project on marine resources.  

Within this particular project area, little or no science was available regarding the baseline occurrence, distribution, or density of some habitats, benthic structures, and species of marine resources.  

In preparation for the EA and associated consultations for the dredge, Cardno was contracted to perform studies that would allow natural resource managers and Navy engineers to manage habitat alteration as a result of future maintenance dredging within Pearl Harbor’s main channel and turning basin.  

Benthic Studies for Pearl Harbor, HI, USA

Our team’s responsibilities during Phase I studies (completed in 2016) involved:  

  • compiling baseline biological and abiotic data into a geodatabase 
  • mapping bathymetric contours 
  • modeling dredge plumes to assist Navy engineers, natural resource specialists, and planners to develop recommendations for the Pearl Harbor entrance channel while also minimizing potential impacts to marine biological resources.  

A key challenge for the team was to develop and address a data gap analysis. Cardno worked closely with our Navy point of contact and regulators to develop a priority list of areas that had no data, and to develop project programs that would fill in the data gaps. As a result of this work, areas of Pearl Harbor are now being restored to original conditions.  

Our team continues to provide assistance with Phase I studies, including in-situ surveys within selected areas and collection of data on coral recruitment. Our Phase II scope focuses on filling high priority data gaps and integrating information into the Navy’s benthic studies geodatabase, including a quantitative evaluation of benthic structure using photomosaic and remote sensing methods.  

Planned additional studies include a benthic survey of the turning basin, water quality assessment, sediment coring, oceanographic measurements, and various comparative assessments.  

In addition, our team has developed an integrated web application to share mapped data developed for this project. Our mapping work has already led to the discovery of a new cultural resource discovery – a previously unidentified wreckage in deep water near Hickam Warf and the crater field.