FEIS - Tahoe Regional Planning Agency

RESPONSE TO COMMENTS ON THE DEIS
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
sediment. The total sediment load reduction predicted by the LSCP model is actually
between 97-100% for Alternative C (C100), of which fine sediments are assumed to
comprise between 60-90% of this total.
Comment 335-h: Comment Summary - Baseline water quality studies need to describe how data relate
to 20-, 50, and 100-year events, first flush events, TRPA Surface Water Discharge
Limits, and a discussion of how the small sample size and non-TMDL sampling
methods affect the results and interpretation.
a) The storms sampled in 2008 and 2009 vary between 0.08 and 1.23 inches of total
precipitin (rain, snow and rain on snow events were captured). The 20yr/1hr storm is
reported at 1 inch over a unit area for the duration of one hour, the 50yr/1hr is
reported at 1.25 inches, the 100yr/1hr is reported at 1.55 inches. b) The samples were
taken as close to the peak as possible to correspond to a "first flush". The difficulty
on measuring this first flush using grab sample methods is noted. c) TSS is Total
Suspended Solids, while SSC is Suspended Sediment Concentration. Both provide a
measure of the non-dissolved particles within a unit of water, the difference arises in
the methods of analysis. See http://water.usgs.gov/osw/pubs/ASCEGlysson.pdf for
more information. d) The DEIS was discussing compliance with TRPA discharge
standards and since TSS is not a TRPA standard, concentrations are discussed instead
of compliance. The results are detailed in DEIS Appendix P and are discussed by
storm event. e) Comment does not require a response. f) Automated samplers were
not used in the pre-project monitoring because of site constraints. Automated
samplers have not been installed to date. The commenter states that TMDL methods
were not followed but does not outlined the methods that should have been followed.
The response assumes that the commenter is referring to sediment loading. Loading
calculations are referenced to Appendix AB. g) See Appendix AB, which presents a
supplemental water quality analysis incorporating DRI data collected on
approximately half of the project area. The DRI studies captured complete flow and
concentration measurements for 12 storm events through January 2008. Note that the
JBR event grab sampling data for 2008-2009 was found to be consistent with the
more complete DRI data. Please see response to comment 79-h.
Comment 335-i: Comment Summary - The EIS cannot evaluate impacts if procedures to treat
stormwater in the underground parking garage have not been developed.
The maintenance of the underground parking garage will be determined for
Alternatives C or D, if selected, and included in the Inspection, Maintenance and
Monitoring Plan (SP-10) prepared for TRPA permitting of the selected Alternative.
Based on communications with IVGID, the existing sewer system can adequately
absorb this wash off if necessary.
Comment 335-j: Comment Summary - The EIS should document the efficacy of pervious pavers and
vacuum sweepers.
A number of studies have been completed for LID strategies in cold weather
climates. The DEIS documents the efficiency of pervious pavers and vacuum
sweepers by reference. The TMDL Pollutant Load Reduction Plan included in DEIS
Appendix R provides further documentation. The remaining comments will be
addressed in the Inspection, Maintenance and Monitoring Plan that will be based on
the selected Alternative as a condition of project permitting.
Please see response to comment 137-e.
SEPTEMBER 8 , 2010 HAUGE BRUECK ASSOCIATES PAGE 8- 145