FEIS - Tahoe Regional Planning Agency

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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 stormwater treatment systems (E20), Alt C with 20yr/1hr stormwater treatment systems (C20), and Alt C with 100yr/1hr stormwater treatment systems (C100) are reported for a variety of water year conditions. Comment 137-d: Comment Summary - Alternatives C and D rely on subsurface infiltration galleries and the DEIS fails to evaluate: 1) loss of gallery efficiency over time due to trash, sediment, organic matter, 2) the cost of maintaining galleries, and 3) Visual inspection of the galleries is inadequate to determine operating efficiency. In addition, there is no comparative analysis of above-ground infiltration galleries. a) Long-term performance of any stormwater treatment system is reliant on the inspections, operations and maintenance of the system. The loss of efficiency over time will be minimized through proper operations and maintenance as determined in the Inspection, Maintenance and Monitoring Plan (SP-10) required for permitting of the selected Alternative. The supplemental analysis does consider the loss of gallery efficiency due to antecedent moisture in the system. The Inspection, Maintenance and Monitoring Plan is a standard practice of the Project (added as SP-10 in Chapter 6). The Plan will be developed for the selected Alternative through an RFP Process that includes a third party agreement between TRPA, Boulder Bay and a consultant. This detailed plan will be based on Chapter 6 of the EIS but can be tailored to the outcome of the Governing Board hearings that will decide the final design of the Project, if approved. b) Because some of the facilities are subsurface, access points are built into the linear treatment system for maintenance and monitoring. The costs associated with maintenance and monitoring will be determined during project permitting because these costs are directly related to the selected Alternative. Although Boulder Bay will be committed to proper maintenance as a conditions of project permitting, the EIS recommends mitigation measure HYDRO-1 to assure that stormwater treatment systems are operated and maintained to be effective in meeting TRPA discharge standards. c) The comment that BMP inspections will only be visually based is incorrect, and the reference to DEIS Appendix G is in error. Appendix G provides the narrative explaining the stormwater treatment system design and routing along with the supporting calculations for summary tables 4.3-5 to 4.3-12. The post project monitoring program will be finalized in accordance with the permitting conditions for the selected Alternative and will most likely include some level of stormwater monitoring in addition to BMP and treatment system inspections. Referencing DEIS Appendix G, the "galleries are designed linearly so that if it occurs that an upstream gallery is clogged or overburdened, the additional capacity in the downstream galleries will absorb some of the overflow". The commenter states that above-grade drainage infiltration galleries are easier to inspect and maintain but provides no supportive data or references. The commenter states that the stormwater treatment system is entirely underground, which is incorrect. The proposed stormwater treatment systems combine infiltration trenches, infiltration galleries (underground) and infiltration basins (above ground) to maximize the capture potential of the project area and increase capacity of the systems. Comment 137-e: Comment Summary - The DEIS needs to provide more information regarding the pervious pavers in Alternative C and discuss their applicability, potential for success, and ability to absorb runoff. UC Davis states they should not be used if surface grade exceeds 5%. How effective are they beyond 5% grade? How will snow removal affect pavers? Discuss where they will be used, the type to be used, and whether they are suitable. Evaluate improper maintenance of pavers. PAGE 8- 54 HAUGE BRUECK ASSOCIATES SEPTEMBER 8 , 2010
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 The commenter states the opinion that plants/vegetation incorporated with pervious pavers will not withstand pedestrian or vehicular traffic and recommends the UC Davis Extension for information on pervious pavers. Pervious pavers are proposed for walkway and patio area that do not have grades exceeding 5%. Roadway areas that use pervious pavers are not expected to exceed 5% grades due to existing grades within the project area. The EIS calculations for stormwater runoff assume a conservative reduction factor of 50% for pervious pavers and not 100% as stated by the commenter. This data is included in DEIS Appendix R, TMDL Pollutant Load Reduction Plan. The comment is noted that sand cannot be used for snow and ice control on pervious asphalt and concrete. The Project proposes the use of automatic snow melting strategies throughout the pedestrian circulation and promenade and roadway interiors (page 4.3-21), however, and does not propose sand application for typical winter operations. The Project also plans for bi-annual spring maintenance of the pervious surfaces with a regenerative microfilter sweeper system to maintain infiltration rates of the pervious pavers. The EIS recognizes that improper maintenance of facilities is a potential impact to surface water quality in impact HYDRO-1. The potential impact is reduced through conformance with TRPA codified regulation (standard practices of the Project for compliance), post-project stormwater monitoring and mitigation measure HYDRO-1. Comment 137-f: Comment Summary - What is the cost of owning and maintaining a regenerative air street sweeper mentioned in the DEIS? Would inclusion street sweeping equipment and a maintenance schedule be included as conditions of project approval? Regenerative air street sweeping equipment is proposed for Alternatives C and D. Boulder Bay will be responsible to the cost of owning and maintaining such equipment. Alternative street sweeping equipment could be required by TRPA as a condition of project permitting. Submittal and execution of the Inspection, Maintenance and Monitoring Plan (SP-10), as based on the selected Alternative, will be a condition of project permitting. According to a study conducted by the Center for Urban Water Resources Management, “the use of permeable pavement systems dramatically reduces surface runoff volume and attenuates the peak discharge during storm events.” Furthermore, they go on to conclude that “A significant contribution of permeable pavements is the ability to reduce effective impervious area, which has a direct connection with downstream drainage systems. This strategy of hydrologic and hydraulic disconnectivity can be used to control runoff timing, reduce runoff volume, and provide water quality benefits.” According to a 2009 study completed by the University of New Hampshire entitled Seasonal Performance Variations for Storm-Water Management Systems in Cold Climate Conditions, the pervious pavement and bioretention systems show minimal to no degradation in either peak flow or removal efficiency performance during cold winter months. Comment 137-g: Comment Summary - The DEIS does not mention potential disadvantages of green roofs (careful design and construction) and lacks critical evaluation. Will construction of green roofs be a condition of Alternative C approval? Green roofs are proposed for Alternatives C and D. The costs for construction and upkeep of green roofs have been incorporated into cost estimates. The Project proponent will assume the responsibility of operating and maintaining the green roofs. The commenter states that there are potential disadvantages of green roofs SEPTEMBER 8 , 2010 HAUGE BRUECK ASSOCIATES PAGE 8- 55
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FEIS - Tahoe Regional Planning Agency

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