The Highridge Water District needs an additional supply of water from Steep Creek. The engineer has selected two plans for comparison:
Gravity plan: Divert water at a point 10 miles up Steep Creek and carry it through a pipeline by gravity to the district.
Pumping plan: Divert water at a point near the district and pump it through 2 miles of pipeline to the district. The pumping plant can be built in two stages, with half-capacity installed initially and the other half 10 years later.
Use a 4O-year analysis period and 8% interest. Salvage values can be ignored. During the first 10 years, the average use of water will be less than during the remaining 30 years. Use the conventional benefit-cost ratio method to select the more economical plan.

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Gravity Intia nvestment Additional investment Pumping $2,800,000 $1400.000 0 200,000 in tenth year replacements. per year year (first i0 years) year (next 30 year) Operation, maintenance. 10,000 25,000 0 50.000 00,000 Average power cost per Average power cost per