MODULES FOR DREDGING AND NO-ACTION SCENARIOS

ERDC TN-DOER-R2

December 2001

to be built within ARAMS for common dredging and disposal operations to facilitate rapid

application of the risk assessment system.

INTRODUCTION: To accomplish this objective several existing support programs and databases

were integrated in FRAMES under ARAMS (Dortch 2001). ARAMS/FRAMES contained tools for

conducting human health and ecological risk assessment, including the Multimedia Environmental

Pollution Assessment System (MEPAS) for conducting human health risk, the Wildlife Ecological

and Assessment Program (WEAP) for conducting ecological risk, and a database containing

chemical-specific parameters required for fate/transport, uptake, and human health effects as defined

by Health Effects Assessment Summary Tables (HEAST) and Integrated Risk Information System

(IRIS). The ADDAMS programs for computing aquatic exposure concentrations, RECOVERY,

DREDGE, and Thermodynamic Bioaccumulation Potential (TBP), and the databases for aquatic

ecological effects, Environmental Residue Effects Database (ERED) and Biota Sediment Accumu-

lation Factor (BSAF), were added to ARAMS/FRAMES for the evaluation of no-action and

dredging impacts.

Figure 2 shows an example of the FRAMES Conceptual Site Model (CSM) interface where the user

formulates the problem (builds a conceptual model for assessing the risk). In the conceptual model

the user selects chemical properties, exposure and uptake parameters, receptors, and effects data,

which are linked with various models. The user then chooses a source model and links it with fate

and transport models to compute exposure and uptake. The exposure and uptake models are linked

with effects assessment and risk characterization models. FRAMES contains the compartmented

MEPAS model.

The implementation of the tools and the development of the no-action and dredging scenarios using

RECOVERY, TBP, BSAF, DREDGE, and ERED are explained in greater detail in the following

section.

MODULES FOR DREDGING AND NO-ACTION SCENARIOS

RECOVERY. RECOVERY is a PC-based screening-level model to assess the impact of contami-

nated bottom sediments on surface waters. RECOVERY was developed for modeling hydrophobic

organic contaminants with a well-mixed water column, but it has been successfully applied to sites

with a variety of contaminants. Contaminants are assumed to follow linear, reversible, equilibrium

sorption and first-order decay kinetics. RECOVERY generates long-term time series of the

concentration profile of contaminants in the sediment and the water column as well as the theoretical

bioaccumulation potential for organisms. These concentrations provide the exposure predictions

for use in risk characterization.

The RECOVERY model incorporated in ARAMS is an extension of versions developed and

modified previously (Ruiz and Gerald 2001; Boyer et al. 1994). As shown in Figure 3, the system

is idealized as a well-mixed surface water layer underlain by a vertically stratified sediment column.

The sediment is uniform horizontally but segmented vertically into a well-mixed surface layer and

deep sediment. The latter, in turn, is segmented into layers of user-defined thicknesses, properties,

and contaminant concentrations underlain by a clean region. The discretized sediment layer

configuration is useful for modeling capping projects and sites where contamination occurred over