Services Rendered:

Biological Evaluation

EFDC Hydrodynamic Model

Dissolved Constituent Analysis

Water Col/Sediment Bed Interaction

Sediment Transport

Environmental Impacts

Client:

Coastline Engineering Achorage, AK, USA and CH2M Engineering for Anchorage Water & Wastewater Utility, Anchorage, AK, USA

Contact:

Doug Jones, CE

John Spencer, CH2MHill

Brett Jokela, AWWU

Dates of Performance:

Oct 2009 to Mar 2010

Status of Project:

Completed

The U.S. EPA review of the Anchorage Water and Wastewater Utility (AWWU) application for renewal of the Asplund National Pollutant Discharge Elimination System permit and associated 301(h) waiver, required a biological evaluation to determine whether permit reauthorization is likely to affect the continued existence of the Beluga whale and other species protected by the ESA, or adversely modify their habitat. Numerical modeling was used to quantify effluent constituent concentrations in receiving waters and sediments affected by the discharge. EFDC was selected as the most appropriate farfield model to address the mixing, fate, and transport of the pollutants of concern. EFDC_Explorer was used to simulate the hydrodynamic and transport processes based on: tidal forcing; density effects; open water and iced-over conditions; an integrated nearfield plume sub-model dynamically coupled to the farfield circulation model; wind-generated currents; inflow from major rivers; and effluent loading from AWWU. The resulting model was successfully calibrated and produced accurate circulation simulations and a nearfield plume dilution study. The model was helpful in providing the ecological risk assessment. The following figures show the suspended sediment mass fractions for various regions in the project area, as well as plan view and profile view of the water column dye animations.