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Home My WebLink AboutWPO200800060 Review Comments Stormwater Management Plan 2008-07-28�pF .AI,g COUNTY OF ALBEMARLE Department of Community Development 401 McIntire Road, Room 227 Charlottesville, Virginia 22902 -4596 Phone (434) 296 -5832 Fax (434) 972 -4126 Project: Plan preparers: Owner /Applicant: Plan received date: Date of comments: Reviewer: Rivanna Plaza [SDP200800090, WP0200800060] Todd Philipp [email: tphilipp @ ddrva.com] Janet Miller [email: jmiller @ddrva.com] Mark Green [email: markg @ecorp- real- estate.com] 24 June 2008 28 July 2008 Jonathan Sharp A. Final Site Plan 1. Copies of all required offsite easements must be provided prior to Final Site Plan approval. [DM] 2. VDOT approval is required [DM] 3. Proposed slopes steeper than 3:1 require low maintenance (not grass) ground cover specified on the plans. [DM] 4. Guardrail with VDOT designations is required for retaining walls next to parking areas or travelways. [18- 32.7.2] 5. All proposed drainage /access /water /sewer easements must be approved prior to Final Site Plan approval. [DM] 6. The sanitary sewer line easement near `B" should extend to both property lines (the line to Kegler's and the line to the daycare). [18- 32.7.4, 32.7.5.2] 7. The drainage line 14 -15 requires an easement (at a minimum extending to the property line). [18- 32.7.4] 8. The Contech Stormwater System is required to be placed in an easement. [ 18- 32.7.4, 32.7.5.2] 9. Drainage easements must adhere to the following criteria (and no less than 20' wide): 10' + (pipe diameter) + 2' + 2 * (depth of pipe — 5'). [DM, 18- 32.7.4, 32.7.5.2] 10. No structures or trees can be placed within drainage easements. [DM, 18- 32.7.4, 32.7.5.2] 11. Parking cannot exceed 5% grade, in any direction. [18- 4.12.15b] 12. Travelway grade cannot exceed 10 %. [18- 4.12.17a] 13. Engineering requires a turn- around for the parking area directly adjacent to the daycare center. Safety is a concern. [18- 32.7.2] 14. Pavement design calculations are required for the proposed Rte. 29 turn lane improvements. 15. A dumpster pad detail is required, with the following minimum specifications: 4' base stone, 6" concrete of 3000 psi at 28 days, reinforced with wire reinforcing or #4 bars at 12" on center. [18- 4.12.19, DM] 16. Typical retaining wall details are required on the plans. A typical manufacture's drawing for segmental block walls, or VDOT reference, is acceptable, with any applicable safety railings or guardrail shown. [DM] 17. Roof drains are required to be shown on the plans, tying into the appropriate drainage structure. [18-32.6.6d.31 18. Albemarle County general construction notes and general construction notes for streets are required to be shown on the plans. [DM] 19. In many instances, spot elevations denoting top of curb (TC) are confusing or incorrect. For example, many of the top of curb elevations are directly on top of parking contours and match Albemarle County Community Development Engineering Review Comments Page 2 of 3 exactly, when there should be 0.5 foot difference for curb height. [18- 32.6.6h.4] 20. Please provide CG -12 for the sidewalk on both sides of the new entrance to Schewel's furniture (currently CG -12 is only shown on one side). 21. Engineering recommends reconfiguring drainage structure 15. As designed, drainage is very close to overtopping the curb during the 10 year storm (D/H is 0.98), and the grading configuration for the parking area draining to the structure is awkward and more than likely will not be implemented correctly in the field. B. Stormwater Management Plan 22. The County currently does not have any design criteria in place for "treatment train" stormwater quality designs. However, as shown, the proposed "treatment train" design appears acceptable. Approval of the design for the proposed plans does not ensure that the design concepts or methodologies will work for future "treatment train" designs. Each "treatment train" design is reviewed on a case -by -case basis by Engineering. 23. No calculations have been provided to show that detention has been met. At a minimum, the following must be provided: [17 -314] • Reference to the allowance of development on TMP's 45 -112C1 and 45 -109 up to a rational method C value coefficient of 0.75 based on the `Berkmar Drive North Extension Existing Kegler's Detention Basin Stormwater Analysis, Jack Kelsey, March 30, 1994" and `Berkmar Drive North Extension drainage map (3/30/94)." • Composite coefficient computations for TMP's 45 -112C1 and 45 -109 showing that the rational method C value coefficient is not in excess of 0.75. • Computations to show that the peak rate of runoff for the 2 and 10 year storm on the Schewel's site is not increasing. 24. Please provide adequate details for each WQ facility (each Filterra, the Stormfilter system, and the hydrodynamic separator). For the proposed Filterras, a detail of each Filterra with appropriate inverts and piping in conjunction with their adjacent inlets must be shown. For the hydrodynamic separator and stormfilter vault, the design configuration and all appropriate invert elevations and piping must be shown. [DM] 25. Albemarle County general stormwater notes are required to be shown on the plans. [DM] 26. Copies of manufactures' approval for the Contech facilities and Filterra facilities are required prior plan approval. [DM] 27. A stormwater facility maintenance agreement and appropriate $17 fee is required. [17 -304E] 28. A SWM bond will be computed by the County once the plans have been approved. C. Erosion and Sediment Control Plan 29. The "stormwater runoff considerations" in the narrative is incorrect. [DM, VESCH] 30. The phasing plan in the ESC narrative contains three phases, and the ESC plans only show two phases. Also, the phasing plans and sequence in the narrative do not appear to correlate. [DM, VESCH] 31. The ESC plans should provide access to Kegler's at all times. Based on the narrative sequence and plans, it difficult to tell if the new access to Kegler's will be constructed prior to the closure of the existing access. [DM, VESCH] 32. The proposed construction entrance is in the way of construction and grading activities. A more suitable location would be off of one of the existing entrances (preferably the Kegler's entrance). [DM, VESCH] 33. Dust Control (DC), Temporary Stabilization (TS), and Permanent Stabilization (PS) symbols are required to be shown on the plans. [DM, VESCH] 34. A staging and parking area, and a stockpile location is required. [DM] 35. Protection must be provided during all phases of construction. Erosion control measures cannot be in the way of grading or improvements. The proposed sediment traps are shown in areas of Albemarle County Community Development Engineering Review Comments Page 3 of 3 proposed grading, buildings, and improvements. [DM, VESCH] 36. Adequate channels [MS -19] must be provided for the site. It appears that MS -19 may be addressed upon the approval of Northtown Center, the proposed development directly downstream Rivanna Plaza, on the other side of Rte. 29 (as the channels downstream of Northtown Center are inadequate and they are currently proposing to making downstream channel improvements). Otherwise, channels downstream of Rivanna Plaza must be adequate until the drainage area of the watershed is 100 times greater than the proposed development, or until the channel reaches the Rivanna River floodplain (whichever comes first). [MS -19, VESCH] 37. An ESC bond will be computed by the County once the plans have been approved.