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HomeMy WebLinkAboutSDP201000021 Review Comments 2010-04-16.. ..� pF A k73' UIRGINZP COUNTY OF ALBENL4,RLE Department of Community Development 401 McIntire Road = Pro Wei-S — Qtl1e� CoL,�►�.e�.-k x aware o� Charlottesville, Virginia 22902 -4596 Phone (434) 296 -5832 Fax (434) 972 -4126 Project: North Pointe Northwest Residential Area SDP - 2010 -00021 and WPO- 2010 -00017 Plan preparer: Mr. Doug March, PE; W & W Associates Owner or rep.: Neighborhood Investments NP -LLC Date received: 4 March 2010 (plan signed 3 March 2010) Date of Comment: 16 April 2010 Engineer: Phil Custer The Final Site, road, SWM, and Site ESC plans for the North Pointe Northwest Residential Area project, received on 4 March 2010, have been reviewed. Engineering review can recommend approval to the plan after the following comments have been addressed. A. General review comments 1. This plan cannot be approved until the submittal for the road stream crossing is approved. The ESC plan for this project will not be able to receive a grading permit until the crossing is established. 2. The current ESC plan shows disturbance to critical slopes that were shown as being preserved in the approved rezoning plan. Because of this, a critical slope waiver must be approved by the Planning Commission before the current plan can proceed or the ESC plan must be redesigned to stay within the limits shown on the plan approved by the Board of Supervisors. 3. Property lines cannot go through buildings unless a substantial fire wall is constructed on the -Koundary. A plat must be submitted and recorded prior to final site plan approval that rectifies this V problem. The simplest solution would be to combine the two parcels with a Boundary Line Adjustment Plat. 4. The plan appears to propose features within the 50ft construction easement granted to the owners of TMP 32 -22K1 in the document recorded in DB 1663, PG 648. The applicant should remove these features from the 50ft easement or amend the agreement so that it works for both parties. 5. Please provide a note on the cover sheet of the plan which states that before a certificate of occupancy is granted, a plat dedicating the ROW, public drainage easements with associated deeds, stormwater management easements, and temporary construction easements must be rec rded. 6. er Proffer 4.1, the County will request that the floodplain be dedicated once the Conditional Utter of Map Revision is approved by FEMA and the county. 7. "Per Proffer 4.4, please provide confirmation that all streambank mitigation required by the Army Corps of Engineers for the Northwest Passage stream crossing is being provided onsite. B. Site Plan review comments (SDP- 2010 - 00021) 1. The placement of buildings 25, 26, and 27 is not in general accord with the approved rezoning plan. Please work with the Planning Department to fmd a solution to this issue before the next submittal. 2. The distance between the private access easement to the church property and Discovery Court is too short for VDOT to provide two entrance permits. These entrances must be either separated to the minimum spacing required by VDOT or consolidated. The resolution to this issue should be addressed simultaneously with the previous comment while in discussion with the Planning Department to assure that the solution is still in general accord with the application plan. 3. The connection to TMP 32 -22K1 must be design and constructed with this development. This travelway must be no narrower than 20ft from curb to curb. The travelway must be design and constructed along the existing access easement unless the access easement is modified. [ 18- 32.7.2.5] 4. If Buildings 25, 26, and 27 is allowed in the current proposed location, the travelway southwest of building 27 must be redirected slightly and extended to the property boundary of TMP 32 -22P [18- 32.7.2.5] 5. Please provide the date of the topographic information. 6. Please provide a benchmark on the plan. 7. Please show the stream buffers on all applicable sheets. Any stream buffer disturbance except exempted items must be mitigated. 8. Please show the approximate locations of the existing and new flood elevation lines. 9. On sheet C -8, please shade all critical slopes and show the approximate limits of critical slope disturbance authorized by the Board of Supervisors at the time the rezoning plan was approved. 10. Please callout the end treatment for each guardrail section. 11. Please separate the drainage and stormwater management easements. 12. The widths of the public drainage easements from structures 34.3 to outfall and 11 to 10 are not correct. [DM] 13. Please show all public drainage easements on the landscape plan to confirm that all significant trees are located outside of the easements. 14. Please provide vertical profiles of the sight distance lines looking north from the entrances south of buildings 11 and 19. The vertical alignment of Northwest Passage seems to obstruct the sight lines. When the road is redesigned, make sure the vertical alignment is corrected to provide adequate sight distance. 15. Please label each entrance with a VDOT designation. 16. Entrances cannot have a slope greater than 4% for the first 40ft from the edge of the curbline. Please revise the spot elevations at the Discovery Court entrance so that the cross slope is as close to 4% as reasonably possible. [18- 4.12.17] 17. VDOT approval of all road plans must be received before the final site plan can be approved by the County. 18. , rbing is required on the landscaped area between parking spaces. Please either revise the site plan or request a waiver from the Zoning Administrator per 18- 4.12.2.c. [18- 4.12.15.g] 19. -11 parking areas and travelways adjacent to parking areas must be no steeper than 5% (this includes all "driveway" spaces adjacent to buildings). This maximum appears to be violated consistently throughout the site. Please either revise the site plan so that no slope is over 5% or request a waiver from the Zoning Administrator per 18- 4.12.2.c. Engineering review does not, recommend approval of this waiver. [18- 4.12.15.c] 20. A few spaces on the south end of building 6 are less than l 8ft long. Please rotate the building so the length meets the minimum requirement for a parking space. [18- 4.12.16.c] 21. Please remove the 2 southernmost parking spaces east of building 1. The spaces are too close to the entrance and create an issue when a vehicle is entering the site at the time another is backing from these spaces. [DM and 18- 32.7.2] 22. The slope of the travelway adjacent to inlet 29 directs concentrated water across the drive aisle. Please regrade the travelway or move inlet 29 so that it is immediately downhill of the nearby filterra. [18- 32.7.2] 23. It appears that an inlet was omitted from the parking area west of building 25. 24. The pipe from inlet 35.1 to 35 is at an acute angle. Please revise the network so that the change of flow direction is at least 90 degrees. [DM] 25. Pull the guardrail behind the fire hydrant north of building 12. �✓' rrl% 26. Remove the sediment trap grading north of the entrance in all sheets but the ESC plan, if necessary. 27. Where is Detail C on Sheet 49 located in the plan? This detail should be removed from the plan if it is not needed. 28. The standard pavement section is adequate for most of the parking areas and travelways outside of the ROW. However, it appears as though a few of the entrances may have ADT's greater than the approximately 260 trips the standard payment section can handle. Please provide a detail that shows the projected ADT's of each travelway and entrance so that the pavement sections can be verified to be satisfactory. [18- 4.12.15.a] 29. Please identify the layback angle of the retaining wall in the detail and consider in plan view the lost rizontal space as the wall height increases. 30. Wbus stop is required on site for the southbound lane of Lewis and Clark Drive. [Proffer 9.2.a] 31. In note #6 on the drainage profile sheets, please clarify that the 4ft drop includes water falling from the inlet to the bottom of the manhole. 32. For all curb inlets that do not have overland flow to SWM facilities, the sizing criteria must use 6.5in/hr. [policy] 33. Structures 2 and 3 should be located at the low point of the roadway. 34. I recommend reevaluating the placement of handicap ramps in parking areas where significant runoff will be traveling in the curbline across ramps. 35. In the Landscape Plan, please provide a low maintenance, non - grassed groundcover on all slopes steeper than 3:1. [DM] C. Road Plan review comments (SDP- 2010 - 00021) 1. Before the final site plan can be approved, all road improvements as outlined in Proffer 5.3.1.c must be approved and bonded. The WPO plans associated with these road improvements must also be approved and bonded prior to site plan approval. The design of two of these road improvements (i and iii) has been included in a plan that was previously submitted to the county (WPO- 2009 - 00067). The other three proffered improvements (ii, iv, and v) have not been included in any plan received by the county. All easements (drainage, SWM, ESC /construction, etc.) and ROW associated with the U4101 of the offsite road improvements must be platted prior to road plan approval. [Proffer 5.3.1.c] 2. Prior to the approval of the plans for improvements at any US Route 29 intersection, Owner shall provide VDOT traffic signal network timing plans that VDOT finds acceptably address the jmpacts of the proposed traffic signals for peak traffic periods. Please provide proof of this ✓approval from VDOT. [Proffer 5.3.21 3. Currently, there is some question as to whether the primary road section for Northwest Passage (Lewis and Clark East) is acceptable to VDOT. If a modification to the typical road section is re uired by VDOT, a variation must be submitted to the Planning Department so that cross - section t P3 as shown on sheet D1 of the Rezoning Plan may be altered to meet VDOT standards. [Proffer 5.11 4. The Right of Way must be placed 1 ft outside of the sidewalk and not on its edge. 5. In the construction set for the extension of Northwest Passage to North Pointe Blvd., the applicant must design and construct a public road to the TMP's 32 -22P and 32 -22G. [18- 32.7.2.5 and 14- 409] 6. Please remove the temporary turnaround from all sheets since the roadway will be constructed to Z North Pointe Boulevard. 7.1 Condition 7 of SP- 2006 -00034 has not been met.' 8. Inlet 2 and 3 should be located at the low point of the road and the low point should be moved farther into the site. 9. Immediately prior to site plan approval, the applicant must submit a road bond request form for each road plan. With each bond request, the applicant must fill out a schedule of completion. All bonds (roads, swm, and esc) must be posted prior to final site plan approval. [Proffer 5.3.1.cl D. SWM review comments (WPO- 2010 - 00017) 1. Approval from Filterra for the current design has been received. If any change to the Filterra watersheds or placement occurs, an updated letter will be required. 2. An approval letter from the manufacturer of the Stormfilter system is required. 3. Please provide a stormwater facility maintenance agreement and fee for each property a facility is located on. 4. I have reviewed the detention waiver request with the County Engineer. The County Engineer will grant the waiver of 2 and 10 year detention for the northern drainage area on the condition that detention is provided upstream of both Stormfilter systems so that the water quality volume is guaranteed to be routed through the water quality units. This must be demonstrated through routings of rational method storms of varying durations. 5. Please show all roof drain collectors on the site plan. Roof drain collectors are required for any portion of any building that does not have overland flow to a drainage inlet. 6. The ARB must approve all design aspects of Stormwater Facility 10. 7. Water quality requirements for the site will be met if the applicant can provide enough detention to route the entire water quality volume through the stormfilter systems. This must be demonstrated through routings of rational method storms of varying durations. 8. For the CN calculation for the post - development drainage area for SWM 10, use higher CN values than 85 and 90 for townhouses because the impervious percentage for this site is greater than the 65% found in the VSMH table. 9. Stormwater Facility 10 must also provide detention for as much of the extension of Northwest Passage (and surrounding land that drains to Northwest Passage) that the stubout from 35.3 would collect. Once the full road plans for Northwest Passage are prepared, the detention calculations can be evaluated again for compliance. 10. For all curb inlets that do not have overland flow to SWM facilities, the sizing criteria must use 6.5in/hr. [policy] 11. The downstream slope of the embankment of SWM facility 10 must be 3:1. [VSMH MS 3.01 -13] When this change is made please make sure the embankment width is compliant with Table 3.01 -1 and the work is shown outside of the conservation area and floodplain. 12. If SWM -10 is to remain a dry detention basin, please provide a low flow channel to the riser from all inlet points. 13. Proffer 9.1 states that the applicant will grant all permanent and temporary easements for the use of SWM facility 10 when the county's school lot is developed. Although the proffers and plan do not explicitly require the applicant of this development (NW residential area) to design or build this facility for the school's stormwater runoff, engineering review understands that the approval of the variation to allow buildings 25, 26 and 27 in the current proposed location is contingent upon the design of several aspects of the land surrounding this facility. As proposed, the intent of the design of SWM facility 10 appears to provide detention of only the impervious area from this development, the Northwest Residential Area (though, see comment 9). It can safely be assumed that the facility would require a considerable expansion in order to satisfy a portion of the school's water quality and quantity requirements. There are two ways the facility could be increased to meet SWM requirements for the future development of the school. Without an easement from the property owner of TMP 32 -22P however, the only option for expansion of the facility would be to the east towards Northwest Passage, which would likely require steep slopes and retaining walls. Because the design of the school site has not be initiated and the ultimate size and shape of the facility is unknown, the applicant must show a temporary construction easement bounded by the property line with TMP 32 -22P (south), the conservation line (west and northwest), the road ROW (east), and a line running from east -to -west at structure 34.1 from the ROW to the conservation area (north). The stormwater quality system must be '%/ . of shown outside of this temporary construction easement. The construction easement will need to be platted prior to approval of the final site plan. The plat should indicate that all of the construction easement is reserved for possible future SWM dedication upon demand of the county when the school lot is developed. 14. The SWM bond will be calculated at the time of WPO plan approval. E. Site ESC review comments (WPO- 2010 - 00017) 1. The current ESC plan shows disturbance to critical slopes that were shown as being preserved in the approved rezoning plan. Because of this, a critical slope waiver must be approved by the Planning Commission before the current plan can proceed or the ESC plan must be redesigned to stay within the limits shown on the plan approved by the Board of Supervisors. Engineering review recommends placing the sediment basin on the access easement to the church property (after coming to a mutually acceptable agreement with the property owner) and phasing the construction of buildings 1 and 2. 2. A portion of Sediment Basin 1 is currently proposed in the conservation area. The program authority will not allow this disturbance inside the conservation area. Engineering review recommends placing the sediment basin on the access easement to the church property (after coming to a mutually acceptable agreement with the property owner) and phasing the construction of buildings 1 and 2. I Please identify separate limits of construction for both this ESC plan and the Stream Crossing Plan (WPO- 2009 - 00061). Please provide notes on Sheets 24 and 25 in the area of the stream crossing that refers to the previously approved plan. Please also refer to the previously approved stream crossing plan in the construction sequence and eliminate the reference to guardrail demolition to establish the entrance; this work will be covered by the other plan. This comment assumes that the plans will not be combined. 4. A grading permit for this project will not be issued until the stream crossing is in place unless the stream cross plan is combined with the site plan set. 5. Per Proffer 4.3.a., this development is required to provide extra erosion and sediment control on site to the satisfaction of the Program Authority. The applicant has identified 6 items that were provided in this plan that he stated were above and beyond standard erosion and sediment control practices. Those 6 items are: l) All 2:1 slopes to have EC -2 lining, or annual rye hydroseed with tackifier. 2) Use of wire - supported fence on the east side of the site bordering NF Rivanna River. 3) For E &S Control Phase 1, the volume of SB -2 is greater than the required minimum by approximately 60 %. 4) For E &S Control Phase 1, the volume of SB -1 will be greater than the required minimum by more than 200 %. 5) Existing sediment traps, silt fence and other E &S control features installed under WPO- 2009 -0061 will remain in place for as long as feasibly possible. 6) Temporary Slope drains will be installed from the outlets of SB -1 and SB -2. Though engineering review considers at least half of these items normal requirements, we will consider this proffer satisfied if the applicant extends the temporary slope drains from Basins 1 and 2 to the stream. The applicant must also place a note on sheets 24 at no heavy equipment Q'l. must be used to install this slope drain and associated riprap SP Condition #41 W�,..�;r� SP � 6. The concept for sediment basin 2 does not seem to work during t e m erme late stages between the two phases. An additional phase to the plan is necessary to clarify the construction sequence. Please provide a phase between the two existing phases that shows what the site would look like the day before Sediment Basin 2 must be removed. The proposed layout, grading, and stormsewer plan appears to require the basin to be removed or affected too soon. Similarly, the changes required to address comments 1 and 2 will likely have the same issue which could be addressed with this intermediate phase sheet. 7. In the Phase I plan, please show the retaining walls needed to install the fill diversions being constructed. The work to install the walls will be performed below the at -grade diversion dikes. 8. Please move the construction entrance for this ESC plan to just east of the diversions so that the entrance can drain to a sediment trapping measure. The construction entrance in phase 1 should be placed on the existing haul road and in phase 2 the entrance should be placed on Northwest Passage. This comment assumes that the plans will not be combined and the grading permit for this plan will be given after CRS and grass has stabilized the majority of the stream crossing plan. 9. In the set, please include the paved wash rack detail found in the county's design manual, available online, and remove the standard detail from the VESCH. 10. Please provide more DC (both phases) and PS (in Phase 2) symbols throughout the plan. 11. Please show a location for a staging and parking area on the plan. 12. Please provide a location for the soil stockpile on the plan. The erosion and sediment narrative refers to an offsite stockpile and waste area plan on another North Pointe parcel. The stockpile must be shown within the limits of an erosion and sediment control plan. 13. Please clarify what Phase 1 mass grading is, as referenced in note 7 of the construction sequence. 14. Please lightly shade or hatch all critical slopes on sheet 24. 15. Please label the proposed drainage areas to basins 1 and 3 on sheet 25. My calculations show the drainage area to Basin 1 being 10.6 acres in Phase 2. 16. The phase 2 portion of the ESC plan appears to have omitted the grading required at Sta. 26 +00 of Northwest Passage. 17. For sediment basin 1, please show the 401 contour in plan view. The actual width of this embankment is only 6ft and must be widened to 8ft. [VESCH MS 3.14] 18. Please provide safety fences surrounding all sediment basins stating "danger, quicksand, do not enter." 19. Please provide the hydraflow routings of the sediment basin to confirm that the 25 -year storm is at an acceptable elevation. 20. For the CN calculation in the sediment basin calculations, use values of 82 (B soils) and 87 (C soils) for exposed earth. Please also consider the impervious area in Phase H in basins 1 and 3 when checking the 25 -year storm elevation. 21. The ESC bond will be calculated at the time of WPO plan approval.