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
ROWs as described in responses to comments 337a and 337b) contribution to runoff
that enters Caltrans drainage systems down gradient to effectively 0 cfs for the
20yr/1hr design storm. Alternatives C and D reduce contributions from the project
area to effectively 0 cfs for the 100yr/1hr storm. Runoff from portions of NDOT
ROWs that are not within the project area could continue to contribute to "pass
through discharge" and enter Caltrans systems, however, but is outside the scope of
the Project. The comment that NDOT agreed to coordinate with the Project to
address interstate flow concerns during the December 5, 2008 meeting is noted.
Comment 337-d: Comment Summary - The existing 18-inch drainage pipe east of Stateline is
inadequate, and NDOT and Boulder Bay agreed (12/08) that it should be replaced by
a larger pipe to accommodate 100-year storm runoff from the entire tributary area
and not just Boulder Bay.
The comment that the existing capped 18-inch pipe under SR 28 would not
accommodate the anticipated 100yr/1hr discharge from the tributary watershed under
existing conditions is noted and is correct. The commenter fails to recognize the
effective removal of this runoff volume under Alternatives C and D, however, which
could negate the need to replace the existing 18-inch pipe. Under Alternatives A, B
and E, only the 20yr/1hr storm volume would be captured and removed from the total
runoff volume and the replacement of the existing pipe could be necessary.
Comment 337-e: Comment Summary - Collection and infiltration of impervious surface runoff does
not fully address the total tributary runoff that contributes to highway drainage.
The stormwater drainage systems are designed to capture, convey and infiltrate
runoff from total contributing areas, including impervious and pervious areas within
the project area and Washoe and NDOT roadways and ROWs included in the project
area and a portion of those up gradient from the project area that contribute runoff to
the project area. See Tables 4.3-5 through 4.3-12 for summaries of total contributing
pervious areas and DEIS Appendix G for the detailed contributing areas. Table 1 is
added in Appendix AB that provides a summary impervious areas/land coverage in
combination with the LID strategies and the associated effective coverage reductions
incorporated into Alternatives C and D, including green roofs, pervious pavers and
bioretention for stormwater filtration systems.
Comment 337-f: Comment Summary - Page 4.3-1 and 2: Project is located in a smaller watershed
than "East Stateline Point watershed tributary area." Provide the actual size of this
smaller watershed and quantify in DEIS.
The East Stateline Watershed is a TRPA priority watershed and is discussed in the
existing conditions because the DEIS is a TRPA decision document. The smaller
subwatershed discussed in the comment was delineated by DRI for the Brockway
Project Area Stormwater Runoff and Characterization Study (Hayvaert et al. 2008)
and Lumos and Associates delineated the contributing watershed areas for the
Boulder Bay project area during the planning and design of the stormwater treatment
systems for the Project. The "brockway" subwatershed is approximately 167.3 acres
as delineated by DRI. Note that this subwatershed area included only half (8.6
acres) of the Boulder Bay project area. Given that the total project area is 16.26
acres, the project area comprises less that 10% of this subwatershed.
Comment 337-g: Comment Summary - Impervious surface runoff may be insignificant compared to
total watershed runoff as discussed in NOP comment letter (8/8/08). Total runoff
may impact highway drainage systems, not just impervious runoff.
SEPTEMBER 8 , 2010 HAUGE BRUECK ASSOCIATES PAGE 8- 153