Powerline Plan and Environ. Assessment Jan. 2013 - Flood Control ...
Powerline Plan and Environ. Assessment Jan. 2013 - Flood Control ...
Powerline Plan and Environ. Assessment Jan. 2013 - Flood Control ...
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<strong>Powerline</strong> <strong>Flood</strong> Retarding Structure<br />
Pinal County, AZ<br />
Draft Supplemental Watershed <strong>Plan</strong><br />
<strong>and</strong> <strong>Environ</strong>mental <strong>Assessment</strong><br />
etc.) <strong>and</strong> maintenance of long-term productivity (e.g. improved flood protection). The NED, EQ,<br />
<strong>and</strong> OSE accounts are discussed below. The RED is not a requirement under P&G <strong>and</strong> was not<br />
considered in this study.<br />
Table 6-1 Summary <strong>and</strong> Comparison of C<strong>and</strong>idate <strong>Plan</strong>s – NED Account<br />
Alternative 1<br />
Alternative 2<br />
No Action<br />
Decommissioning/NED<br />
Project Investment $212,700 (O&M) $23,893,800<br />
National Economic Development Account (NED)<br />
Beneficial Annual 1/ $0 $0<br />
Adverse Annual (Project<br />
costs <strong>and</strong> maintenance)<br />
$212,700 $1,006,700<br />
Net Beneficial ($212,700) ($1,006,700)<br />
1/ The proposed project will provide an estimated $14,779,300 in average annual equivalent damage reduction benefits. However, as<br />
the "no action" or future without project alternative also provides this same benefit stream, the project does not have a positive<br />
incremental benefit. The benefits of the project are tied to reducing the risk of catastrophic failure of the existing structures <strong>and</strong> thus<br />
reducing the risk to life <strong>and</strong> property, as described in the plan.<br />
The effects of the alternative plan in terms of the NED account are summarized in Table 6-1 above.<br />
The project investment cost includes the construction cost, mobilization, contingencies, engineering<br />
<strong>and</strong> design, supervision <strong>and</strong> administration, construction surveying, stormwater pollution<br />
prevention plan, <strong>and</strong> real estate, if required.<br />
Benefits for the project were based upon the reduction of flood damages. <strong>Flood</strong> damages under<br />
both a With Dams <strong>and</strong> Without Dams scenario were estimated. The difference in flood damages<br />
between the two scenarios can be considered a benefit of retaining flood protection. Because both<br />
of the alternatives, including the No Federal Action/Future Without Project, continue to provide<br />
flood protection throughout the project life, the benefits are same for each alternative.<br />
The adverse annual costs include the investment cost amortized at a discount rate of 3.75% over a<br />
period of 103-years plus the annual maintenance costs. The net beneficial amounts are computed as<br />
the annual benefits, less the adverse annual costs.<br />
The above economic evaluation is documented in the report titled “<strong>Powerline</strong>, Vineyard Road <strong>and</strong><br />
Rittenhouse <strong>Flood</strong> Retarding Structures Supplemental Watershed <strong>Plan</strong>/<strong>Environ</strong>mental <strong>Assessment</strong><br />
Economics Evaluation Technical Memor<strong>and</strong>um” (Gannett Fleming Inc. <strong>Jan</strong>uary, <strong>2013</strong>). The<br />
economics evaluation memor<strong>and</strong>um is summarized in the “Investigations <strong>and</strong> Analysis Report” in<br />
Appendix D.<br />
Under Alternative 1 (No Action <strong>Plan</strong>) the existing <strong>Powerline</strong> FRS <strong>and</strong> IDSM would remain in place<br />
<strong>and</strong> would continue to provide flood protection benefits up to the 100-year event until the end of<br />
the <strong>Powerline</strong> structure design life (year 2017). Flows in excess of the 500-year event would be<br />
USDA- NRCS Page 6-9 <strong>Jan</strong>uary <strong>2013</strong><br />
Kimley-Horn <strong>and</strong> Associates, Inc.