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HomeMy WebLinkAboutSDP201000091 Review Comments Minor Amendment 2011-08-16ALg�,�� �'IRGINZ� COUNTY OF ALBEMARLE Department of Community Development 401 McIntire Road Charlottesville, Virginia 22902 -4596 Phone (434) 296 -5832 Fax (434) 972 -4126 Project: Treesdale Park; WPO- 2010 - 00078; SDP - 2010 -00091 Plan preparer: Mr. Scott Collins, PE; Collins Engineering Owner or rep.: Albemarle Housing Improvement Program, Inc. Date received: (Rev. 2) 15 July 2011 (Rev. 1) 25 May 2011 3 December 2010 Date of Comment: (Rev. 2) 16 August 2011 (Rev. 1) 1 June 2011 17 January 2011 Engineer: Phil Custer The second revision to the amendment to the site, ESC, and SWM plans for the Treesdale Park Project (original site plan: SDP - 2010 - 00013; original WPO plan: WPO- 2010 - 00011) has been reviewed. The following comments are provided. A. SDP - 2010 -00091 General Comments 1. Please mimic the sheet numbering system of the previously approved plans so it's clear what sheets are being modified and which are remaining the same. (Rev. 1) Comment has been addressed. 2. Please provide the county with the Army Corps of Engineers permit for the temporary disturbance needed to install the storm line across the intermittent stream. (Rev. 1) Comment has not been addressed. The letter referred to by the applicant in his response letter did not accompany the resubmittal of the plan. (Rev. 2) Comment has been addressed. 3. If no changes are proposed on sheet 8, then please remove it from the set. If there are modifications shown on this sheet, please identify them. (Rev. 1) This comment should be handled by the county planner. I'll note that new sheet DP- 3A is modifying a profile that appeared on sheet DP -3. 4. Similarly, if no changes are proposed on sheet 13, then please remove it from the set. (Rev. 1) Comment has been addressed. B. SDP - 2010 -00091 Minor Site Plan Amendment Comments 1. References and callouts to the previous stormsewer alignment are still shown on the plan. Please revise these notes and remove the proposed riprap from the channel that was to be placed above the pipe disturbance. (Rev. 1) Comment has been addressed. 2. Please provide a safety slab on structure 4D. (Rev. 1) Comment has been addressed. 3. Anchor blocks are needed on pipe 4C. Please use the same note that was provided for pipe from structure S24. (Rev. 1) Comment has been addressed. 4. The drainage system south of building 2 cannot drain to structure 34 without lowering the invert of the VDOT structure significantly. This would require VDOT approval. The pipe from the roofdrain collection system to structure 34 is further complicated by the foundation of the wall. Please provide a detail of how this pipe is to pass through the wall. It may be difficult to get all of the roofdrains of building 1 to structure 32 as well. What are the inverts of some of the southwestern cleanouts? (Rev. 1) Comment has been addressed. 5. In the area of the new wall, please refer to the wall rail detail on sheet S -5 of the original site plan. (Rev. 1) Comment has not been addressed. 6. (Rev. 1) The SWM amendment proposed by the applicant will eliminate the stormwater quality and quantity treatment for most of the Stonewater parcel. Therefore, please revise all applicable sheets in the site plan set eliminating all proposed impervious area not draining to the new biofilter as shown on SWM -1 of the latest plan submittal. This will require most of the 15 Stonewater Sheets within the approved Treesdale site plan to be revised with this amendment. (Please note that the Stonewater road set - SUB - 2007 - 00077 -does not need to be amended.) (Rev. 2) None of the last 20 sheets of the Treesdale final site plan appear to be amended with this application. In my opinion, the county cannot approve this plan until several of these sheets are modified to match what is shown on ESC -4A and SWM -1. However, site plans and site plan amendments are the domain of the Agent, which in this case is the Chief of Current Development. Since he is reviewing this amendment as well, I will defer to him regarding what needs to be amended on which sheet of the original final site plan. I have conferred with the County Engineer and we are in agreement that the ESC and SWM sheets are acceptable except the few minor changes detailed below. C. WPO- 2010 -00078 Stormwater Management Plan Comments (Amendment to WPO- 2010 - 00011) 1. The county is under the impression from statements made by both applicants' representatives over the last several years and the agreement recorded on DB 3775 PG645 that both Stonewater and Treesdale are committed to a jointly used facility at the location of the recorded swm easements. This SWM plan amendment appears to disrupt this commitment. The County Attorney's office will need to review the applicable agreements and determine if and how Community Development can approve such an amendment. The plan is also confusing on many levels. To name a few points of confusion: • The only modifications to the stormwater sheets appear to be the addition of new contours into the previously approved proposed contours of the enhanced, extended - detention facility and the addition of an underdrain system. • All of the enhanced, extended detention facility details (including the Landscape Schedule) of the previously approved plan are still on sheet 12 even though it is clear that a biofilter is being shown over 90% of the facility. • The wetland planting plan is still shown on the plan view detail on sheet 12. • According to the plan view detail on sheet 12, the stormwater facility will no longer treat runoff from majority of the Stonewater development. Such a reduction would require a drastic alteration to the existing ESC plan. • The modified simple spreadsheet has not been updated based upon the proposed bypass of the majority of the Stonewater drainage area. • The routing and downstream channel calculations have not been updated after the reduction to the volume of the facility. The problems above are not the only point of confusions on the project. I recommend the applicants meet with staff to discuss the reasons for this submittal and potential solutions. (Rev. 1) The applicant has chosen not to meet with county staff regarding the SWM plan but has made strides in providing clarification of this plan amendment's intention. The following comments must be addressed before the plan can be approved: a. Stormwater plan amendments are not treated as intermediate plans. This plan will replace the previously approved Treesdale plan (WPO- 2010 - 00011). When Stonewater wishes to develop, a new ESC and Stormwater plan must be submitted to the county for review and approval. The ESC plan for the Stonewater development will not be allowed to disturb the existing Treesdale biofilter at that time. Please modify all notes in the set to reflect this situation. (Rev. 2) Please remove the last sentence of the Stormwater Management Note on the cover sheet. Please remove "Future storm sewer from Stonewater shall outfall into future enhanced extended detention facility" on sheet SWM -2. Both of these notes imply that the next plan or concept has been approved. As discussed in the meeting between the applicant and the county, the Stonewater development will likely construct an embankment at the property line for an independent sediment basin and SWM facility. b. Please remove all references to the "previously approved Stonewater plans" throughout the set. The Stonewater plan (WPO- 2007- 00045) was superceded by the Treesdale plan (WPO- 2010 - 00011) which is only active plan for the area and is being amended with this current application. (Rev. 2) Comment has been addressed. c. Please remove all references to the extended detention facility and modify the plan and all details removing all design elements of the extended detention facility. (Rev. 2) Please refer to comment La. d. Please modify the plan so that there is no stagnant water, other than the forebay for the biofilter. Please provide a positively sloped channel from the natural gulley on the stonewater site to the facility's riser. The lowest elevation of the riser should also equal the lowest elevation of the basin. The inverted riser should be removed and replaced with a regular orifice with a trash rack meeting state requirements identified in USMH 3.02. Please update the routings accordingly. (Rev. 2) Comment has been addressed. e. Given the elevation of the spillway out of the biofilter of 387 and the required removal rate of the facility (requiring a depth of Ift), the bed elevation must be 386. Please clearly label this in plan view and in both cross - sectional details and revise the design of the facility accordingly. The routing calculations must also be modified. (Rev. 2) Comment has been addressed. f. The two details showing the riser are inconsistent. (Rev. 2) Comment has been addressed. g. The applicant has accidentally omitted the lawn impervious load in the modified simple spreadsheet which has affected the removal rate calculations. Please revise accordingly. (Rev. 2) Comment has been addressed. h. The stormwater plan must consider the sidewalks associated with the private road and Stonewater Drive. (Rev. 2) Comment has been addressed. The 385.5 contour area measures closer to 5700sf than the 7600sf as claimed by the applicant. Please redo the area calculations for the biofilter. (Please note that the county accepts a bed area equal to 4% of the upstream impervious area in order for a biofilter to treat at a 65% removal rate (assuming I ft of ponding). Considering comment g and h, the required footprint is likely close to 5500sf). Please revise the routings accordingly. (Rev. 2) The biofilter footprint is satisfactory. 2. If a biofilter is still being proposed, a revised landscape plan is required. The plan must show 1 planting for each 100sf of biofilter bed area. The landscape plan must possess a shrub -to -tree ratio between a 2:1 to 3:1. There must also be 3 species each of tree and shrub. (Rev. 1) The three species requirement assumes that the species are evenly specified so that in the case that one species doesn't flourish in the biofilter facility, 213 of it will still be covered. (Rev. 2) Comment has been addressed. 3. If a biofilter is still being proposed, a revised section of the biofilter meeting all state and county requirements is required. (Rev. 1) Comment has not been addressed. The biofilter embankment must meet the embankment standards of VSMH 3.01. A minimum width of 8ft is required. A 3:1 downstream slope is required. A 2:1 upstream slope is required. (Rev. 2) Comment has been addressed. 4. If a biofilter is still being proposed, the overflow from the biofilter must be a rigid surface like a concrete weir, wall, or other drainage structure. A grass or riprapped overflow is too variable and susceptible to erosion. (Rev. I) Comment has been addressed. 5. Since this plan is proposing to replace the existing stormwater management plan (WPO -2010- 00011), new stormwater facility management maintenance agreements will be needed. An agreement on TMP 61 -184 will currently be required because the embankment of the stormwater facility will be provided on that property. (Rev. I) Through discussions with the County Engineer it is my understanding that the previously recorded maintenance agreements are acceptable. 6. If any variation of a SWM amendment is approved, another bond computation may be necessary. (Rev. 1) A revised SWM bond will be necessary. After plan approval, please send to the County Engineer a completed Bond Estimate Request Form. (Rev. 2) Comment remains unchanged. D. WPO- 2010 -00078 Erosion and Sediment Control Plan Comments (Amendment to WPO -2010- 00011) 1. Please modify the limits of disturbance so that all proposed work within the lines. (Rev. I) Comment has been addressed. 2. If the revised ditch grading west of the offsite sanitary sewer work appeared on the previous ESC plan, please include the grading on this amendment (currently 14). (Rev. I) comment has been addressed. 3. The revision to the ESC measures and limits on the Treesdale parcel (61 -182) does not necessitate any modification to the ESC bond. However, depending on the resolution achieved after the meeting suggested in comment Cl, the limits of disturbance of the ESC plan will need to be reduced and a bond reduction would be justified. (Rev. 1) The SWM amendment proposed by the applicant will eliminate the stormwater quality and quantity treatment for most of the Stonewater parcel. Therefore, the majority of the Stonewater subdivision cannot be constructed. Please include in the ESC amendment all applicable sheets necessary to revise the construction limits to only authorize the construction of the Stonewater roads draining to the biofilter as shown on SWM -1. (Rev. 2) On sheet ESC 4 -A, please add a note that states the following: "This sheet replaces Sheet 2 and 3 of the approved Treesdale ESC Plan WPO- 2010 -00011 and the limits of construction and improvements on the Stonewater property is restricted to what is shown on this sheet." Also, Stonehenge Way is shown as being constructed on the ESC sheet but is not included on the Storm water Management Plan sheet]. Please make the WPO plan consistent regarding what construction is authorized. For the Treesdale project, it does not matter whether Stonehenge Way is constructed now or with the Stonewater development as long as the plans are sheets are consistent and Stonehenge Way is being treated adequately by the biofilter. I will note that the connection to Stonehenge will help towards meeting the traffic signal warrants. File: E3_mia esc swm _PBC_wpo201000078- sdp201000091 Treesdale Amendment.doc