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HomeMy WebLinkAboutSDP201000021 Review Comments 2010-04-16 (2)led K7S- �'IRGINIP COUNTY OF ALBEMARLE Department of Community Development 401 McIntire Road 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. (ASK GLENN AND BILL about timing) 2. The current ESC plan shows new disturbance to critical slopes that were absent 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 else 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 boundary. A plat must be submitted and recorded prior to final site plan approval that corrects this issue. The simplest solution would be to combine the two parcels. 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 on 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. Bill- Must all offsite road improvements be shown in this site plan or because we are bonding the improvements before site plan approval, can the plans be separate? 6. B. Site Plan review comments (SDP- 2010 - 00021) 1. The current site plan does not appear to be in general accord with the approved rezoning plans and the variation approved by the Planning Department. The retaining wall on the west side of the site has grown significantly in length and height, the sediment basin and associated regrading has been proposed in a location where disturbance was not expected, and the orientation of all the buildings and access around Discovery Court has been modified. These discrepancies must be rectified through the Planning Department prior to final site plan approval. 2. The distance between the private access easement 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 in discussion with the Planning Department. r.. NOW 3. The connection to TMP 32 -22K1 must be design and constructed with this development. This ; travelway will be deemed a private street and must be designed to the standards determined by the Chief of Current Development. [18- 32.7.2.5] 4. 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 will need to 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 approval given 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 easement. 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 three plans must be received before the final site plan can be approved by the County. 18. Curbing is 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. All 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. [I 8-4.12.15.c] 20. A few spaces on the south side of building 6 are less than 18ft 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 direction of flow is at least 90 degrees. [DM] 25. Pull the guardrail behind the fire hydrant north of building 12. 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 v the ROW. However, each of the four entrances, Discovery Court, and the travelway from the southern portion of building 19 to building 15 must be upgraded to a more substantial section. Please provide a detail that shows the projected ADT's of each travelway so that the pavement section 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 the lost horizontal space as the wall height increases. 30. A bus stop is required on site for the southbound lane of Lewis and Clark Drive. [Proffer 9.2.a] 31. The drainage profiles must show the crossings of all water and sewer laterals. 32. 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. 33. Please explore alternatives to providing a drainage pipe at a slope steeper than 16 %. Before the county accepts a pipe for maintenance over 16 %, other designs should be explored. 34. For all curb inlets that do not have overland flow to SWM facilities, the sizing criteria must use 6.5in /hr. [policy] 35. Structures 2 and 3 should be located at the low point of the roadway. 36. The placement of handicap ramps in parking areas should consider the placement of inlets and significant runoff across the ramps. 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. Lc must be approved and bonded. 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, and ESC /construction) and ROW associated with the development 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 impacts of the proposed traffic signals for peak traffic periods. Please provide proof of this approval from VDOT. [5.3.2] 3. Based upon comment 8 in VDOT's email dated 7 April 2010 and Proffer 5. 1, a variation must be submitted to the Planning Department so that cross - section NWP3 as shown on sheet D1 of the Rezoning Plan may be altered to meet VDOT requirements. [Proffer 5.1 ] 4. The pavement section designed by the applicant uses just the projected traffic of this development. Considering the future single family homes in the northeast corner of the development, the school site, and the yet to be constructed 2nd entrance at Northside Drive, the pavement section should consider the full ADT. 5. The Right of Way must be placed 1 ft outside of the sidewalk and not on its edge. 6. In the construction set for the extension of Northwest Passage to North Pointe Blvd., the applicant must design a public road connection to the TMP's 32 -22P and 32 -22G. [18- 32.7.2.5 and 14 -4091 7. Please remove the temporary turnaround from all sheets. 8. The site walls at the stream crossing appear to have been replaced by two standard guardrails. Since the site walls were shown on the plan approved by the Board of Supervisors, the retaining walls are required. Since these site walls will act as a guardrail, the walls must be structurally approved by VDOT. 9. Condition 7 of SP- 2006 -00034 has not been met. 10. 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. 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 and placement occurs, an updated letter will be required. 2. An approval letter from the manufacturer of the Stormfilter system is required. %004 44 3. Please provide a stormwater facility maintenance agreement and fee for each property a facility is located on. (Glenn, do we do anything differently if the county will wind up maintaining Facility 10 ?) 4. The majority of this site has no detention provided. The applicant has provided a drainage area map of Flat Branch and wishes to compare the amount of development being released without detention to the whole watershed as justification. The 1 % rule is mentioned. However, the I% rule is mostly referenced when trying to find the termination point for adequate channel calculations, which is an Erosion and Sediment Control requirement. And though the development area that must be compared to the whole watershed of Flat Branch is the entirety of the North Pointe Development because it was planned as one unit, engineering review will not require a channel adequacy analysis of Flat Branch itself Regarding detention, in Albemarle County, all developments over an acre must provide detention onsite. [17 -314] For an exemption of this requirement, please provide the County Engineer with letter with this request per 17 -314G. 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. Should we count the Contech Stormfilter in series as 60 %Removal rate? We are looking at Phosphorous in addition to sediment, yes? 8. GLENN AND MARK- use of contech without upstream detention using only a 0.35in/hr water quality rate (show them my graph) 9. 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 these items is greater than 65% used in the VSMH table. Using the 85 and 90 curve numbers basically counts the grass areas twice because 10. Stormwater Facility 10 must also provide detention for as much of the extension of Northwest Passage (and surrounding land that drains to Northwest Passage depending on the grading) the drainage system which is routed to structure 35.3 collects. 11. The downstream embankment for SWM facility 10 must be 3:1. [VSMH MS 3.01 -13] When this change has been made please make sure the embankment width is compliant with Table 3.01 -1. 12. If SWM -10 is to remain a dry detention basin, please provide a low flow channel to the riser. 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 or plan do not explicitly require the applicant of this development (NW residential area) to design or build this facility for the County'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 designed, SWM facility 10 has been sized only to provide detention for this current application's runoff (see also comment 10). It can safely be assumed that the facility would require a considerable expansion in order to satisfy the school's water quality and quantity requirements. There are a two ways the facility could be increased to meet SWM requirements for the schools development. But, without an easement from the property owner of TMP 32 -22P, the facility would need to expanded to the east which would likely require significant retaining walls ( >10ft) between the facility and the travelway behind buildings 26 and 27. Before any variation is approved, engineering recommends that the applicant design (but not necessarily construct fully) a BMP that meets both stormwater quality and quantity requirements for the future development of the school site to the county's satisfaction. E. Site ESC review comments (WPO- 2010 - 00017) 1. Gfdsgfdg 2.