Identifying the Base Condition

ERDC TN-DOER-C27

July 2002

reported costs. Some examples of total project costs and cost estimating sheets for soil remediation

projects, however, can be found in U.S. Environmental Protection Agency (USEPA) (1999).

This technical note introduces a planning level approach to making cost comparisons between

disposal and process alternatives and quantifying volume reduction, or volume recovery, potential.

Site-specific cost information should be used when possible; cost ranges reported herein should be

used primarily as a "reality check." Cost estimates falling significantly outside the cost ranges

reported for similar projects should be closely scrutinized to determine the basis for the difference.

Detailed costs should be developed for potentially viable alternatives based on the planning level

cost-benefit analysis. These costs should be used in conducting a detailed economic analysis for

the project.

ECONOMIC ANALYSIS: The benefits of physical separation and mechanical dewatering of

dredged material are based on the next least cost dredged material disposal alternative. In the

absence of separation and dewatering processing, the analyst must identify the most likely future

dredged material disposal alternative (the base condition). Potential quantitative benefits of physical

separation are reductions in cost and increases in revenue from the base condition to the physical

separation alternative. The analysis assumes the in situ volume of sediment to be dredged will be

the same for all alternatives.

Identifying the Base Condition

Step 1: Determine the period of analysis. Corps planning studies typically use either a 50- or

100-year planning horizon; however, a shorter period may be appropriate for the analysis of physical

separation projects. The period of analysis should be of sufficient length to allow a life-cycle

analysis of the benefits and cost of all alternatives.

Step 2: Define the project scope. Estimate the quantity and timing of dredged material to be

disposed over the life cycle of the project planning horizon.

Step 3: Define the dredging and disposal alternatives. Disposal alternatives may include CDF

disposal, a combination of CDF disposal and offsite disposal, or offsite disposal.

Step 4: Determine the base condition. From the available alternatives, determine the least-cost

method of dredging and disposal without physical separation. This will establish the Base Condition

from which to measure benefits of physical separation.

1. This analysis compares the cost of alternative dredging and disposal scenarios. The

scenarios may assume different dredging technologies, different transportation methods and

offloading costs at an offsite disposal area or CDF, and/or the cost of developing a disposal site.

For example, when available CDF capacity is limited, material may be disposed offsite, dredging

may be done with a smaller dredge (requiring less settling freeboard), or CDF capacity may be

increased. The combinations of offsite disposal and CDF facilities (existing and developed) must

be of sufficient size to receive the quantity estimated in Step 2. New CDF sites will incur site

acquisition, permitting, and design cost and may require additional transportation cost. The