FEIS - Tahoe Regional Planning Agency
FEIS - Tahoe Regional Planning Agency
FEIS - Tahoe Regional Planning Agency
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RESPONSE TO COMMENTS ON THE DEIS<br />
B o u l d e r B a y C o m m u n i t y E n h a n c e m e n t P r o g r a m P r o j e c t E I S<br />
Treatment System) added in Appendix AB of the <strong>FEIS</strong>. This supplemental analysis utilizes preproject<br />
monitoring data (DEIS Appendix P) in combination with Desert Research Institutes (DRI)<br />
data (Brockway Project Area Stormwater Runoff and Characterizations Study, Heyvaert et al.<br />
2008) linked to daily climate data from wet and dry water years (including El Nino events) in the<br />
Load Simulation Prediction in C++ coefficients (LSPC) to provide more robust estimates of total<br />
sediment (TSS) and fine sediment (FSP) load reductions from the project area.<br />
The simulated scenarios include stormwater management programs (SWMPs) designed for the<br />
following four conditions:<br />
• Existing Conditions (EC);<br />
• Existing Conditions retrofitted to treat the TRPA 20yr/1hr design storm total runoff<br />
volume (E20);<br />
• Alternative C (Proposed Project) built to treat the TRPA 20yr/1hr design storm total<br />
runoff volume (C20); and<br />
• Alternative C (Proposed Project) built to treat the 100yr/1hr total runoff volume (C100).<br />
The supplemental analysis addresses the question: What is the benefit of implementation of<br />
SWMPs for C100 vs. C20? Boulder Bay does not claim CEP credit for reductions of C100 vs.<br />
EC. The “over and beyond” of the Project is only communicated for C100 vs. E20 and C100 vs.<br />
C20. Table 8.5-1 summarizes the predicted runoff results. For E20, C20 and C100, the SWMP<br />
contains all of the project area runoff in the event of a 20yr/1hr storm. The total runoff, including<br />
NDOT and Washoe County ROWs for the 20yr/1hr storm is 16,428 cubic feet (CF) for E20, 0 CF<br />
for C20, and 0 CF for C100. In the event of a 100yr/1hr storm event the total runoff for the<br />
project area, including ROWs, is 37,920 CF for E20, 21,488 CF for C20 and 0 CF for C100.<br />
Stormwater runoff that leaves a project area contains sediment, including fine sediment, nitrogen<br />
and phosphorus, the primary elements leading to the loss of Lake clarity in Lake <strong>Tahoe</strong>. In order<br />
to more clearly understand the potential for runoff from the project area and the conceptual<br />
design capacities of the SWMPs, a number of precipitation situations were modeled, including:<br />
multiple back-to-back storms; longer duration storms; fall, winter and spring timed storms; and<br />
the impact of periodic events such as El Nino years. The goal of the SMWP is to maximize<br />
containment and treatment of runoff volumes.<br />
SEPTEMBER 8 , 2010 HAUGE BRUECK ASSOCIATES PAGE 8- 13