Sierra Colina Village
P. O. Box 129
Lake Tahoe, NV 89448

Planning for...
LEED* Green Certification
Energy Star Rating
Pedestrian & Bike Trails
All Fire Sprinklered Homes
Preserving Open Space
Moderate Income Homes

Recognizing the importance of stormwater quality in the Lake Tahoe Basin, Sierra Colina has expressed a desire to exceed minimum regulatory requirements and typical standards of practice in its design of its permanent BMP plan.  Sierra Colina retained the well-respected Northwest Hydraulic Consultants (nhc) as its water quality design engineer to develop a stormwater management plan and a private stormwater maintenance program plan designed so the proposed stormwater facilities perform consistently over the long-term. The Sierra Colina Project’s stormwater treatment and maintenance plan is designed to substantially exceed existing regulatory requirements for stormwater runoff in the Lake Tahoe Basin. (See Sierra Colina Village DEIS Chapter 2-Project Description, pages 2-39 to 2-44.)

After completing the stormwater management plan for the Project, nhc led the Urban Uplands and Groundwater Source Category Group (UGSCG) for Phase 2 of the Lake Tahoe TMDL.  The UGSCG assessed pollutant loading associated with urban storm water runoff for the Lake Tahoe Basin and produced Chapter 3 of the TMDL Pollutant Reduction Opportunities (PRO) Report (LRWQCB and NDEP, 2008).  Chapter 3 of the PRO Report provides results that were used to inform the Lake Tahoe Watershed Model to simulate pollutant load reductions associated with varying levels of urban storm water quality improvements at the Tahoe Basin spatial scale. nhc has also been retained by TRPA and Lahontan on other matters.

The Sierra Colina Project’s Stormwater Management Plan proposes implementation of a system of storm water management BMPs that is comparable to the highest pollutant load reduction analyzed in the Lake Tahoe TMDL for localized urban storm water quality improvement projects-TMDL Tier 2 Treatment levels (See Sierra Colina Final EIS, Master Response F at pages 2-251 through 2-253). The proposed storm water BMPs are linked together in a series, or treatment train, that includes multiple processes of runoff reduction, pollutant source controls, detention, particle settling, and filtration to reduce pollutant loads. The permanent BMPs and storm water facilities proposed in the Stormwater Management Plan (see Appendix F of the Sierra Colina DEIS) are consistent with the Advanced/Intensive Practices Treatment controls (TMDL Treatment Tier 2) proposed in the Lake Tahoe TMDL Pollutant Reduction Opportunity (PRO) Report (Lahontan RWQCB and NDEP March 2008). The PRO report includes the results of investigations by experts in the field of stormwater treatment. The investigations were conducted by teams of experts referred to as Source Category Groups (SCG).  Each SCG focused on evaluating pollutant control options for each major source of pollutants entering Lake Tahoe, which include atmospheric sources, urban upland and groundwater sources, forest upland sources, and stream channel sources. The PRO Report  process included technical evaluation of pollutant control methods and resulted in a ranking of pollutant control methods based on effectiveness. 

The Stormwater Management Plan for the Sierra Colina Village Project would include the following design elements which exceed existing TRPA Codes and which are consistent with a TMDL Tier 2 stormwater treatment system:

• Sediment traps and drop inlets
• Stabilized road shoulder (curb and gutter)
• Treatment vaults using filtration technology
• Primary snow storage locations draining to the treatment vaults
• Individual driveway stormwater treatment units for down sloped driveways
• Maintenance program funded by a HOA budget and implemented at regular seasonal intervals and after significant runoff events.
• Rigorous Inspection of BMPs & Clean-out of collection facilities
• Sweeping of impervious surfaces associated with the road, snow storage locations and pedestrian paths

Sierra Colina will be the first private residential project in the Lake Tahoe Basin to meet the TMDL Tier 2 level standard for storm water treatment. A TMDL Treatment Tier 2 design achieves the highest pollutant load reduction analyzed in the Lake Tahoe TMDL for localized urban storm water quality improvement projects (See nhc Supplemental Water Quality Analysis at pages 3-4, Sierra Colina Final EIS (Appendix AA) for further analysis).

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