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HomeMy WebLinkAboutSUB201200010 Review Comments Road Plan and Comps. 2012-02-15ALg�,�� �'IRGINZ� COUNTY OF ALBEMARLE Department of Community Development 401 McIntire Road Charlottesville, Virginia 22902 -4596 Phone (434) 296 -5832 Fax (434) 972 -4126 Project: Old Trail Creekside Phase II of Phase III; Road, ESC, and SWM Plans SUB - 2012 -00010 and WPO- 2012 -00008 Plan preparer: Mr. Scott Collins, PE; Collins Engineering Owner or rep.: Mr. Jackie Shifflett Date received: 17 January 2012 Date of Comment: 15 February 2012 Lead Engineer: Phil Custer The construction plans for Phase II of Old Trail Creekside Phase III, received on 17 January 2012, have been reviewed. These plans can be approved after the following comments have been addressed: A. General Review Comments 1. Bonus density was granted to this development for the dedication of open space on the assumption that a trail system was installed by the developer. While the trail standard did not seem to be specifically identified, it is clear from the review of Board of Supervisor meeting minutes that the trail must at least meet the standards of a Class B type 2 path which includes a 10% maximum longitudinal slope and a 2% maximum cross slope. These standards also require a drainage system be designed as if it were a public road. For this path, this requirement will cause a channel to be created on the uphill side of the path with culverts directing the concentrated water to the stream at adequate points. Calculations for the channels and culverts as well as a grading plan meeting the Class B Type 2 standards must be provided on the next submittal. The ESC plan must include the construction of the path within the Limits of Disturbance and protect the construction per the State Handbook. 2. Details of all footbridges proposed with this plan must be provided in this set. Bridge profiles with computations showing the deck has freeboard on the 10 -year storm must also be provided. (Please note that future development plans will need to analyze the stream channel for adequacy so it is recommended that the applicant be conservative when designing the footbridge.) 3. Please move the sanitary sewer line as far as practical away from the stream on lots 14 -16. If allowed by ACSA and VDOT, the sewer line should be able to cross the stream above the culvert when the next phase is constructed. [17- 319.B.1] 4. All references to Mount Vista Lane must be replaced with Windmere Lane. 5. Please supply a mitigation plan for the disturbance to the stream buffer proposed with this plan. [17 -321] B. Road Plan Review Comments (SUB- 2012 - 00010) 1. VDOT approval is required. At the time of this letter, VDOT approval has not been received. VDOT will need to make a determination what subdivision street standards apply to this phase, since new standards were approved in 2009. Please copy me on all correspondence with VDOT so I can be kept in the loop regarding the required road standards. 2. Please provide all horizontal design information (PC, PT, Radius, etc.) on S -1, or provide a new sheet with this information, so a complete road plan review can be performed. 3. Please show sight distance triangles on S -1. 4. Please label the stop and street name signs at the end of Wellbourne. 5. Please provide speed limit signs on all roads. 6. Please provide a note on each drainage profile sheet that IS -1 is required on all structures where there is a drop of 4ft, including from the surface to the bottom of the structure. 7. Please specify a sump on structure Y -2 in the plan and profile. Please specify the grate type on the yard inlet as well. 8. Please update the County's General Notes for Street plans. The first note refers to county inspections. The county no longer inspects streets that are to be accepted by VDOT. 9. In plan view, the side slopes from the roadways are graded at 2:1 but are marked as 3:1 in the road sections. Please correct this discrepancy. Except at the stream crossing, I recommend the use of 3:1 slopes since these slopes are going to be in front lawns. 10. Please show CD -1's and CD -2's in the road profiles where required. 11. Please specify an end section and outlet protection at the end of pipe 83. C. Stormwater Management Review Comments (WPO- 2012 - 00008) 1. The Lickinghole fee for all of Old Trail Creekside Phase III was paid with WPO- 2006 - 00019. The fee was processed for 48 acres of development. 2. A detention waiver for this project was granted with preliminary plat, SUB - 2005- 00259, with the condition that downstream channel calculations were provided confirming adequacy and the first 1 /z" of runoff was treated in addition to the Lickinghole fee. 3. Please modify the biofilter bed cross - section detail so there is not a slope to the media mix. In other words, make sure the boundary between the biofilter media mix and the existing soil is a vertical line. In most facilities, a small slope is negligible to the effectiveness of the facility. But, considering the small width, a sloped biofilter bed in this facility would not operate properly. 4. Please remove all references in the plans to "Luckstone" biofilter mix and replace with "State - Approved Mix." 5. The two biofilter sections in the plan do not match. It seems the one in the upper left corner of SWM -1 should be removed. 6. Nearly all volume -based stormwater quality features in the Virginia Stormwater Management Handbook require sediment forebays. Biofilters are no exception. Please provide a sediment forebay equal to 10 -20% of the bed area in this facility. A simple stone ring, similar to the outlet of the sediment trap, would suffice in separating the biofilter forebay from the main cell without any other changes to the plan being needed. 7. Please move the spillway so that it is in cut and not over fill until the toe of the embankment is reached. 8. There are two bridges shown in the biofilter detail. Please delete the incorrect one. The bridge will need to be relocated to address the previous comment. 9. The Pre - Development condition must be based on what the site looked like before the approval of the previous biofilter plan. In other words, no development should be shown. 10. Please make the length and width dimensions in the plan view detail of the biofilter detail easier to read. Please also label the proposed contours in the plan view biofilter detail. Please do not provide contour lines for any elevation below the bed elevation of 703.5. Please dash the contour line for 703.5 so the dimensions stop at a line. 11. In the biofilter section detail, please specify an impervious core, cutoff trench, and the elevation of the 100 -year storm showing at least 1 ft of freeboard. 12. The Post - Development drainage area map is not correct in the upper reaches of the watershed around Three Board Lane. 13. Before a grading permit can be issued, the WPO bond must be posted. To receive a WPO bond estimate, please provide a completed Bond Estimate Request Form to the County Engineer. Both property owners will need to sign the request document and be party to the bond and grading permit. D. Erosion and Sediment Control Review Comments 1. The maximum watershed for a diversion dike (DD) is 5acres. Please replace the DD on the west side of the construction limits with a designed diversion (DV) channel. Please provide calculations supporting the size of it. Please alter the horizontal placement of it so a minimum slope of 0.5% is provided and no fill is required to construct it. 2. Please show a Construction Entrance (CE) in phase H. 3. In both phases, please provide a RWD across the construction entrance and provide a DD to the sediment basin. 4. Please show the maximum drainage area to sediment trap 1. The two maximum drainage areas should overlap because of changes to the watershed from Phase 1 to Phase 2. 5. The baffle does not increase the flow path as much as intended by the applicant. 6. Please provide Inlet Protection (IP) on structures 38 and 38B. 7. Please label the scale of the sediment basin detail. 8. Please move the spillway so that it is in cut and not over fill. 9. Please clarify the 25 -year freeboard analysis on the sediment basin. When looking at Table 3.14.0 and Plate 3.14 -8, it seems to me the freeboard on the 25 -year storm is less than lft. 10. Please update the County's General Notes for Erosion and Sediment Control plans. 11. Please provide outlet protection at the end of pipe 83. 12. Adequate channel calculations have not been provided. Please refer to the latest edition of the County's Design Manual for expectations for the submittal of adequate channel calculations. 13. Before a grading permit can be issued, the WPO bond must be posted. To receive a WPO bond estimate, please provide a completed Bond Estimate Request Form to the County Engineer. Both property owners will need to sign the request document and be party to the bond and grading permit.