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HomeMy WebLinkAboutWPO200800045 Review Comments Erosion Control Plan 2008-08-14ALg�,�� �'IRGINZ� COUNTY OF ALBEMARLE Department of Community Development 401 McIntire Road Charlottesville, Virginia 22902 -4596 Phone (434) 296 -5832 Fax (434) 972 -4126 Project: WPO- 2008 - 00045, SDP - 2008 -00074 Blue Ridge Co- Housing Plan preparer: Mr. Kevin Conner, CLA; Gay and Neel Inc. [kconner @gayandneel.com] Owner or rep.: Crozet Co- Housing, LLC fax (unknown) Date received: (Rev. 1) 31 July 2008 29 April 2008 Date of Comment: (Rev. 1) 14 August 2008 15 May 2008 (SRC Final Site Plan Comments) 13 June 2008 (Road Plans, SWM Plans, ESC Plans) Engineer: (Rev. 1) Phil Custer Jonathan Sharp A. Final Site Plans (comments from 15 May 2008) 1. Please provide copies of federal and state permits for stream disturbance (Army Corps, VDEQ, etc.). (Rev. 1) Comment has not been addressed. 2. Please provide a completed copy of the standard stormwater maintenance agreement and fee for recordation for the proposed stormwater management facilities. (Rev. 1) Comment has not been addressed. 3. Please provide the FEMA map and date references labeled for the FEMA floodplain. (Rev. 1) Comment has been addressed. 4. Please provide all copies of necessary offsite easements. For example, easements to construct water and sewer, road improvements, offsite construction and access easements, drainage easements, etc. (Rev. 1) Comment has not been addressed. The only offsite easement obtained has been for the construction within the private ROW. Permanent easements are needed for this project that must be obtained before approval is granted. Temporary construction easements also appear necessary on adjacent parcels affected by the roadway upgrade and construction of the SCC's to the streams. 5. The proposed adjacent subdivision and boundary line adjustment must be recorded prior to final site plan approval. (Rev. 1) Please adjust site plan set to match the approved boundaries. 6. Please provide traffic generation figures for the proposed site and proposed roadway improvements. (Rev. 1) Comment has not been addressed. The applicant has just mentioned the estimated traffic generation for the proposed development and has not offered an estimate of the traffic load existing on Park View Drive. This is needed in order to check the road is designed to the correct standards. 7. Curb and gutter and treated surfaces based on VDOT regulations and standards are required for all travel -ways and parking areas. As proposed, the plan requires a waiver of curb and gutter and parking /travel -way surface requirements. If you want to pursue a waiver of the requirements, please provide a waiver request which includes the items requesting to be waived and a justification in accordance with the Code Sections provided below: Curb and gutter waiver request: Curb and gutter can be waived administratively for stormwater management purposes by the County Engineer according to Code Section 18.4.12.15g. For all other purposes, a curb and gutter waiver can be administratively waived by the Zoning Administrator in conjunction with the County Engineer according to Code Section 18.4.12.2c2. Parking and travel -way surface waiver request: Parking and travel -way surface requirements can be waived by the county Engineer according to Code Section 18.4.12.15a. (Rev. 1) I have forwarded your request for a waiver of the curb and gutter to the Zoning Administrator. I will forward you her response once it is received. I have also noticed that the site plan is not in compliance with sections 18- 4.12.17.a and 18- 4.12.16.c.6 and requested that the Zoning Administrator make decisions on these waivers as well. The County Engineer has approved your request for the alternative surface requirements. These details cannot be amended without County Engineer approval. 8. The proposed plan is showing stream buffer disturbance. Stream buffer disturbance should be minimized. Engineering recommends minimizing stream buffer disturbance along Parkview Drive and eliminating all stream buffer disturbance shown on site, except for any necessary ditches to convey the outletting drainage of the facilities to the streams below. Any stream buffer disturbances will need approval from the Program Authority, and require an approved Mitigation Plan prior to Final Site Plan approval. (Rev. 1) The disturbances of the stream buffer for temporary ESC controls as shown on the latest plan will be allowed through section 17 -320B of the Water Protection Ordinance. Comments from the mitigation plan review for the disturbance of the stream buffer for the upgrade of Park View Rd. will appear in the sections to follow. 9. The grading plans show proposed slopes steeper than 2:1. Please revise the grading plans so that all proposed slopes are 2:1 or flatter. Some of the proposed spot elevations are very confusing. For example, the spot elevation 651.9 near the existing barn/shed is very close to the existing 650 contour, creating very steep slopes in this area. There are other proposed spot elevations which create very steep proposed slopes. (Rev. 1) Comment has not been addressed. 10. For SWM facilities with embankments 3 feet or higher, the downhill face of the embankment must be minimum of 3:1. Several of the proposed embankments are only 1.5:1. (Rev. 1) Comment has not been addressed. SWM facility 3 has an embankment taller than 3ft and the slope varies between 3:1 and 2:1. Please amend. 11. All proposed slopes steeper than 3:1 must have low maintenance (not grass) ground cover specified on the plans (site plan and road plans). (Rev. 1) Comment has not been addressed. The groundcover must not be grass. For instance, juniper would be something that would meet the requirement. Also, not all slopes steeper than 3:1 are shown with the special low maintenance groundcover designation. 12. Safety railing must be specified for retaining walls over 4 feet high. (Rev. 1) Comment has not been addressed. 13. Adequate access must be provided to all of the SWM facilities. The requirements are: 10 feet wide access not exceeding 20% in grade. For grades in excess of 10%, graveled access is required. Access must be provided to the embankment, any outlet structures, and any forebays. (Rev. 1) Comment has not been addressed. Please clearly show the access paths on the plan. 14. All entrances must be shown with a VDOT designation. (Rev. 1) Comment has been addressed. 15. Please show the sight distance lines at the entrance of the site on Parkview Drive. (Rev. 1) Comment has not been addressed. A vertical profile of this sight line may be needed because of the existing grading of Park View Drive. 16. VDOT approval is required for any work affecting the public right -of -way. (Rev. 1) VDOT approval has not yet been received. 17. Parking areas cannot exceed 5% in grade, in any direction. (Rev. 1) Comment has been addressed. 18. The proposed parking area configuration does not meet County requirements. In order to maintain 9 foot wide parking spaces, a 24 foot wide travel -way must be provided. If a 20 foot wide travel - way is provided, parking spaces must maintain 10 feet in width. (Rev. 1) Comment has been addressed. 19. Guardrail is required for the stream crossing along Parkview Drive. (Rev. 1) Guardrail placement is not correct. The shoulder needs to be 7ft wide and the guardrail should be placed in the outer 3ft to maintain the required clear zone. Please see VDOT manuals. 20. It appears that the concept for Stormwater Management is not capturing as much proposed impervious area as practicable. It appears that parking areas and structures may bypass the facility. Typically, roof drains of structures tie into the proposed stormwater management facilities, and parking areas /travel -ways are directed to the SWM facilities through use of curb and gutter, piping, or ditches and swales. Any concentrated discharges flowing in to a SWM facility require forebays. (Rev. 1) Comment has not been addressed. Grading around the parking lot and travelway adjacent to SWM 3 indicates that not all stormwater could be captured. It appears a curb along the travelway from SWM 5 to SWM 3 would collect this water. All other site runoff appears to be directed to facilities through roof drains, channels, or overland flow. Also, forebays have not been provided for any of the biofilters. Forebays are required at all concentrated discharge points. The forebay should be sized to hold at least 0.1 " of runoff from the impervious area. This volume can be included in your Water Quality volume of the biofilter so the footprints do not need to be increased. 21. Please indicate the outlet locations of the proposed SWM facilities. Also, show the required improvements in order to provide adequate channels for the outlets of the facility to the streams below. (Rev. 1) Please show the grading and lining necessary for all stormwater conveyance channels on the site plan. 22. We received a copy of you SWPP permit. This should be sent directly to DCR. Please contact Mr. Matthew Grant, DCR, at 804.225.3068 for more information. This does not affect your review /approval of this plan. (Rev. 1) Comment has been noted by the applicant. 23. Engineering has not yet been able to complete the review of the ESC plans. However, after a quick look at the plans, it appears that the plans are inadequate. Use of only silt fence as ESC protection is inadequate. For adequate perimeter control, please provide diversion dikes which convey drainage to sediment traps and basins. (Rev. 1) ESC comments will be given in the ESC section of this letter. 24. The ESC plans appear to indicate that the SWM facilities will be constructed during the same time that the grading /site construction occurs. SWM facilities cannot be constructed or retrofitted from sediment traps to biofilters until after final stabilization has occurred. (Rev. 1) Comment has not been addressed. Please remove biofilter grading from the ESC plan. Traps I and 2 do not appear to be graded to the areas listed in the calculations. 25. The road plans, drainage plans, ESC plans, SWM plans, and mitigation plans, any easement plats, subdivision plats, and boundary line adjustments must be approved and/or recorded prior to final site plan approval. (Rev. 1) Comment has not been addressed. Engineering review cannot recommend approval to the site plan until all comments are addressed. 26. More comments may be necessary upon resubmittal. a. (Rev.]) Please provide a detail or call out a specific product number for the Enviroform wheel stops. The proposed wheels stops must be all the requirements listed in section I8- 4.12.16.3. b. (Rev. 1) Is there a storm drain located adjacent to Building I ? If so please provide calculations, outlet protection, a profile, and all other requirements listed in the design manual. c. (Rev. 1) The sanitary force main is being shown through inlets, water meters, fire hydrants, and storm manholes. Please correct. Please also show the ROW and property boundaries on sheet 8A. d. (Rev. 1) The intersection of travelways adjacent to the 2 -story log dwelling does not meet the county's standard for safe and convenient access. The northern travelway is at too steep of a grade. The intersected travelway is also at a cross 10% slope which is far to great. Please reduce to a grade no steeper than 5 %. B. Road Plans 27. Adequate conveyance of drainage must be provided for Parkview Drive. The ditch shown opposite of the development ends at contour 646. An adequate channel must be provided to the channel below. There does not appear to be any adequate ditches or conveyance on the roadside directly adjacent to the development (from the high point 16 + 00 to the channel below the culvert.) It appears drainage may spill into the street. (Rev. 1) Please show the necessary grading all channels including the SCC's along Park View Drive. A drainage easement will be necessary if a ditch leaves the ROW. Also, the ditch calculations are confusing. I do not see how any of the roadside ditches can have a 10 year flow of 40.04cfs. Please amend calculations for SCC8. Also, there appears to be 4 separate channels along Parkview Drive. There should be 4 separate calculations: SCC8, 9, 10, and 11. The side slopes of the ditch in the computations must match the roadway section (3:1). 28. Please provide pavement design calculations. (Rev. 1) Comment has not been addressed. 29. A traffic generation and distribution summary (ADT's) and design speed limit are needed for design of Parkview Drive (for road width, K values, pavement design, etc.) (Rev. 1) Comment not addressed. The applicant has just mentioned the estimated traffic generation for the proposed development and has not offered an estimate of the traffic load existing on Park View Drive. This is needed in order to check the road is designed to the correct standards. 30. Please show all existing and proposed signs for traffic control (speed limit, stop signs, etc.) (Rev. 1) Comment has not been addressed. Stops signs are needed from Parrot Creek Rd. and the site at Sta. 11 +00. The sign at Sta. 11 +00 should be placed before the bike path. A speed limit sign should be shown for the lane traveling from Route 240. Please specify what the speed limit and design speed for the roadway upgrade are. 31. Please show all existing and proposed street name signs. (Rev. 1) A street sign needs to be shown at the intersection of Park View and Route 240. 32. Please provide the Albemarle County general construction notes, and notes for streets on the plans, verbatim (It appears old notes are provided.) A copy of the latest notes is provided at the end of this comment letter. (Rev. 1) Comment has not been addressed. 33. Please show cross drain locations labeled with VDOT designations (CD -1,2) at every major cut and fill transition or sag curve on the road profile sheet. (Rev. 1) Comment has not been addressed. Please remove the note and locate the cross - drains in the profile meeting the VDOT requirements. 34. The pavement crown must be specified at' /a ":1' slope. (Rev. 1) Comment has been addressed. 35. The roadway shoulder must be a minimum of 4' width. (Rev. 1) It appears there are many discrepancies between the roadway section and plan view/ The grading in plan view seems to indicate that the shoulder is not graded at 1 /a " /1'. Please correct. There doesn't appear to be a shoulder on the west side of the road from Sta. 14 +00 to 15 +75. Please correct and show grading for the ditch and provide an easement. Easements will be needed overall roadside ditches outside of the ROW. The section should show a fill slope at the edge of the bike path. 36. Proposed slopes steeper than 3:1 must have low maintenance (not grass) ground cover specified. (Rev.]) Comment has not been addressed. The groundcover must not be grass. Juniper would be something that would meet the requirement. Also, not all slopes steeper than 3:1 are shown with the special low maintenance groundcover designation. 37. Guardrail must be specified over all fill slopes and culverts, with 3' additional shoulder, using VDOT designations. Guardrail end sections must be labeled. (Rev. 1) Comment has not been addressed. The shoulder has not been increased an additional 3ft when the guardrail is necessary. Guardrail is needed over a larger span than what is specified. The guardrail should be accounted for in the roadway section as well. 38. Ditches must be dimensioned at F depth min., and 4' min. width from shoulder to ditch centerline. (Rev. 1) Comment has been addressed. 39. Please provide a profile for the roadway culvert. (Rev. 1) The profile of the roadway culvert is adequate but a drainage easement will be needed over the pipe where it exists outside of the ROW. The easement should be placed at the width specified by the formula in the design manual. 40. Please provide culvert calculations. (Rev. 1) Comment has not been addressed. The computations appear to be for the existing culvert that will be replaced with this plan. 41. Please provide ditch calculations. (Rev. 1) All grass -lined ditches must have side slopes of 3:1. If side slopes are steeper, the channel must be lined with rip -rap because of the county's policy of not allowing grass on slopes steeper than 3:1. Please show accurate grading reflecting the width of the channel on sheet 7. For instance, SCC7 is shown as I ft wide on the plan but is Oft wide in the calculations. 42. Please provide outlet protection and outlet protection calculations for the roadway culvert. (Rev. 1) Comment has not been addressed. Please show the outlet protection dimensions in the plan set. 43. Please show the drainage area drainage to the proposed culvert. (Rev. 1) Comment has been addressed. C. Stormwater Management Plan 44. Stormwater Management drainage area maps (proposed and existing) must have the acreage coefficient, and time of concentration labeled for each drainage area on the maps. (Rev. 1) Drainage area lines do not look accurate. Please amend. Also, show the proposed contour lines on the "Post Development Drainage Area Map ". 45. It appears that not all impervious areas drain to the SWM facilities. See comment #20. (Rev. 1) Grading around the parking lot and travelway adjacent to SWM 3 indicates that not all stormwater could be captured. It appears a curb along the travelway from SWM 5 to SWM 3 would collect this water. All other site runoff appears to be directed to facilities through roof drains, channels, or overland flow. 46. Please provide ditch calculations for all proposed ditches conveying flow to SWM facilities. (Rev. 1) Please show the grading for channels and include in the limits of disturbance on the ESC plan. Please also see comment 41. 47. The Stormwater Management facilities must not be located within the stream buffers. (Rev. 1) Comment has been addressed. 48. Flow in the facilities must not be short - circuited. The flow path must be 2:1 or greater in all water quality facilities. (Rev. 1) Comment has not been addressed. 49. Cross - section details of each facility must be provided, including: embankments, principle and emergency spillways, sediment forebays, and biofilter floor dimensions. See the County Engineering design manual checklist for all cross - section detail requirements. (Rev. 1) The provided details are missing critical pieces of information. Please list the embankment elevation, embankment width, bed elevation, spillway elevation and TOW (if applicable). And, for all biofilters adjacent to walls, please show the gravel backfill behind the biofilters and any tie backs and how it relates to the mix in the biofilter. Engineering review is concerned about water escaping the mix without treatment by passing through the backfill. Please also provide details for the spillway through the retaining wall. 50. For facilities with embankments 3 feet or higher, the 10 yr. and 100 yr. high water elevations must be shown on the cross - section details. With an emergency spillway, 1 foot of freeboard for the 100 yr. storm must be provided. Without an emergency spillway, 2 feet of freeboard for the 100 yr. storm must be provided. (Rev. 1) Comment has not been addressed. It appears that all facilities lack adequate free board. 51. Areas of sheet flow draining into biofilter facilities must be protected from erosion by appropriate scour protection stone or energy dissipation measure. (Rev. 1) Comment not addressed. The applicant has referred to a VDOT standard detail that is not appropriate for this use. Please specify on the plan the size, depth, and any other necessary characteristics of scour protection for each biofilter. 52. Plants must be shown and labeled with height or caliper in the biofilters. Three species of trees and three species of shrubs are required in each biofilter. (Rev. 1) Comment has not been addressed. Each facility needs to have 3 species of trees and 3 species of shrubs specified where possible. 53. The minimum depth of sand/soil media in biofilters is 2.5 feet. (Rev. 1) Please amend the plan to indicate 1.5ft of gravel as the underdrain. All references to the Luckstone mix should be removed and replaced with "State Approved Mix': All underdrains must be 6" in diameter as well. [DM] 54. The outlet of the facilities must be shown on the plans and cross - sections, matching the computations. (Rev. 1) Comment has been addressed. 55. Biofilter underdrains and cleanouts must be shown on the plans. Clean -outs are required at each junction and 50'. (Rev. 1) Comment has been addressed. 56. Please provide the Albemarle County general stormwater notes on the plans. Notes are provided at the end of this comment letter. (Rev. I) Comment has been addressed. 57. The 100 yr. storm elevations are shown at a lower elevation than the 2 and 10 year storm. This does not make sense. The critical duration storm must be used for the 100 yr. storm. Detention requirements are for the 2 and 10 yr. storm only, the 100 yr. storm does not need to be detained. The routings for the 100 yr. storm are required to show that the freeboard requirements are met for facilities with embankments 3 feet in height and above. (Rev. 1) Detention calculations for Basin I do not appear correct. Please clarify. In the calculations, the crest length for SWM 4 is listed as 12ft as opposed to 2ft on the plan. Please adjust. Freeboard requirements do not appear to be met. 58. A SWM bond will be computed by the County once the plans have been approved. (Rev. 1) Comment has been noted by the applicant. D. Mitigation Plan 59. A mitigation plan is required for any stream buffer disturbance. Please provide a mitigation application, plan, and fee. a. (Rev. 1) Please provide the disturbance detail showing a shaded areas of the proposed stream buffer disturbance so that the 0.32 acres can be confirmed. This area must match the ESC plan. [DM] b. (Rev. 1) Please submit maintenance agreement for the mitigation planting area. [DM] c. (Rev. 1) Please provide a maintenance narrative and schedule on the plan that includes the completion date. [DM] d. (Rev. 1) Please show adequate channels from each biofilter through the buffer. [DM] e. (Rev. 1) The planting locations for each of the landscape categories (canopy tree, understory tree, and shrub) should be heterogeneous. The shrubs, canopy trees, and understory trees should not be grouped together in bands but mixed. 60. A Mitigation bond will be computed by the County once the plans have been approved. (Rev. 1) Comment has been noted. E. Erosion and Sediment Control Plan 61. It appears that inadequate perimeter control is provided. See comment #24. (Rev. 1) Comment has not been addressed. a. The construction of ST -1 will require a retaining wall. This wall needs to be the first measure installed and should be noted in the construction sequence and shown on sheet 4. b. The grading for the sediment traps 1 and 2 are not correct. It appears the grading is being shown is the grading of the biofilters which appear on sheet 7. Please correct. It is difficult checking the compliance with the sediment trap calculations without the necessary grading. Additional comments may be necessary once the grading is shown. 62. Silt fence must not be used across contours in place of diversion dikes. Silt fence is limited to areas of sheet flow with 1/a acre per 100ft of level on -grade silt fence. (Rev. 1) Comment has been addressed. 63. Please provide ESC measures for the road improvements and sewer line improvements. (Rev. 1) Comment has not been addressed. The grading for the sediment traps need to be shown. I do not see any ESC measures for the construction of the sewer line. 64. Stream crossings and diversions must be provided at all stream crossings. A detailed sequence of construction must be provided for the replacement of the existing culvert and work within the live stream. (Rev. 1) Comment has not been addressed. 65. The County Erosion Control notes must be shown on the plans. Notes are provided at the end of this comment letter. (Rev. 1) Comment has been addressed. 66. The limits of clearing and grading encompassing all disturbances must be shown on the plans. (Rev. 1) Comment has not been addressed. 67. Please graphically show the construction entrance on the plans. (Rev. 1) A construction entrance will be needed at Park View Rd's intersection with Route 240. Please provide a narrative regarding when the road upgrade will take place. 68. Please show existing drainage divides. (Rev. 1) The "Pre- Development Drainage Area Map" appears to be incorrect in the delineation of area 5 and 3 and should match the map lines on the sediment trap area map. The sediment trap drainage area map also does not seem to match the ESC plan. The drainage areas for traps 3 -6 also needs to be shown in the map. 69. Please show existing soil boundaries with labels. (Rev. 1) The map in the narrative is illegible. 70. Please show a stockpile location. (Rev. 1) Comment has been addressed. 71. Please show a staging and parking area. (Rev. 1) Comment has been addressed. 72. Please show outlet protection at all outlets. (Rev. 1) Comment not addressed. It appears there is a low point and inlet protection on the plans adjacent to building 1, but there is no accompanying outlet protection or storm sewer system proposed anywhere on the plan. This system will need a profile. Also, it appears a culvert is needed at the site entrance off of Park View Dr. and outlet protection should be provided. A profile of this culvert will also be needed. 73. All ESC measures must remain outside of the stream buffers. (Rev. 1) The disturbances of the stream buffer for temporary ESC controls as shown on the latest plan will be allowed through section 17 -320B of the Water Protection Ordinance. 74. Adequate channels (MS -19) are required at each facility outlet and at the outlet of all ditches and culverts. (Rev. 1) Please see comment 41. 75. A paved construction entrance detail is required for the plans. A copy of the detail is attached following the comments. (Rev. 1) Comment has been withdrawn. 76. An ESC bond will be computed by the County once the plans have been approved. (Rev. 1) Comment noted. 77. (Rev. 1) Please show tree protection to the proper VESCH standard or remove completely from the plan if the tree protection is not required through the ZMA or other agency review. Many trees are called out as having tree protection fencing but the placement of the fence is not shown. The state standard requires fencing at the dripline for each tree. The site plan shows disturbances well within the dripline. File: Mew swm rp fsp mp_PBC_sdp08074 + wpo08045 Blue Ridge Co- Housing