Page 45 - Water and wastewater engineering

1-16 WATER AND WASTEWATER ENGINEERING

TABLE 1-5
a
Comparison of design alternatives by equivalent costs
b
Equivalent Costs
Cost Items Alternative A Alternative B
Capital costs

Construction cost $6,300,000 $5,300,000
Engineering 945,000 795,000
Land 130,000 200,000
Legal, fiscal, administrative 50,000 80,000
Interest during construction 189,000 159,000
Subtotal $7,614,000 $6,534,000
Inflation prior to construction 228,000 196,000
Total capital costs $7,842,000 $6,730,000
Annualized capital cost c 557,000 478,000
Operating and maintenance costs
Personnel 220,000 290,000
Power 120,000 60,000
Chemicals 15,000 128,000
Miscellaneous utilities 30,000 30,000
Miscellaneous supplies and materials 50,000 50,000
Annual operating and maintenance costs $ 435,000 $ 558,000
Total annual costs d $ 992,000 $1,036,000
a
Adapted from Water Pollution Control Federation, MOP 8, Wastewater Treatment Plant Design, Washington. D.C., 1977.
b
Cost basis 2006. Engineering News Record Construction Cost Index 7690.72.
c
Also called “debt service.” Capital cost recovery factor (A/P, 5%, 25) 0.0710.
d
Annualized capital cost annual operating and maintenance costs.
alternatives, the consequences of deciding one alternative over another, and the data and/or logic
the engineer used to arrive at the consequences.
In the iterative process of design, the engineer must return to this step each time the list of al-
ternatives or the cost estimates change to verify the original decision or to make a new decision.

Preliminary Design
At this stage, the engineer is given approval to perform the initial stages of design. This stage of
design is to allow a more rigorous comparison of the alternatives that appear to meet the goals of
the client.
The engineer develops a work plan and schedule. These provide the client with realistic ex-
pectations of the timing of the project, while ensuring that the level of effort and degree of detail
developed by the engineer are appropriate for making decisions about the economic feasibility
of the project.