HomeMy WebLinkAboutSDP201000013 Review Comments Final Site Plan and Comps. 2010-03-08ALg�,��
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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 - 00011; SDP - 2010 -00013
Plan preparer: Mr. Scott Collins, PE; Collins Engineering
Owner or rep.: Albemarle Housing Improvement Program, Inc.
Date received: 16 February 2010
Date of Comment: 8 March 2010
Engineer: Phil Custer
The final site, ESC, and SWM plan for Treesdale Park Project has been reviewed. The following
comments are provided.
A. SDP - 2010 -00013 Final Site Plan Comments
1. This final site plan shows more disturbance to critical slopes than the plan accompanying the
critical slopes waiver that was approved by the Planning Commission in the fall of last year.
Because of the increase in critical slope disturbance, it is my opinion that a critical slope waiver
must again be granted by the Planning Commission. This decision can be overturned by the Chief
of Current Development, who is the acting agent of the Zoning Ordinance for this project.
2. VDOT approval is required. At this time, VDOT approval has not yet been received.
3. An area for a bus stop, as required by Proffer 5, must be accounted for in this plan. This bus stop
will require the dedication of additional ROW in the future. The placement of Building 1 must
consider adjustment of the setbacks because of the future ROW dedication.
4. All Right of Way needed for this development on TMP 61 -184 must be dedicated before the
approval of this final site plan.
5. The construction and permanent (drainage and greenway) easements on TMP 61 -184 must be
recorded before this final site plan is approved.
6. The construction and permanent easements on TMP 61A -A must be recorded before this final site
plan is approved.
7. The boundary line adjustment combining all parcels into one must be recorded prior to approval of
this final site plan.
8. Streams and wetlands are located within the limits of construction. Please provide an approval
letter from the Army Corps of Engineers. If the applicant contends that streams or wetlands will
not be impacted, please provide a letter from the Army Corps of Engineers that confirms this
statement.
9. Please show all of the existing easements recorded with SUB - 2008 -00253 on the plat with the
deed book and page number listed. [18- 32.6.6]
10. Please add more TOW/BOW spot elevations on the retaining wall along Rio Road and remove the
note referencing a height of 7ft.
11. Please specify the two terminals of the guardrail along Rio Rd.
12. The layback angle of the segmental retaining wall used should be considered in the layout of the
site plan. For every 5.3 vertical feet, the wall loses Ift horizontally. For the series of walls on the
west side of the property, the lost space will likely not be an issue. However, the slope of the
retaining wall should be considered for the wall along Rio Rd. Please show the true thickness of
this wall, from the face at the bottom and from the back edge at the top. This will likely
necessitate moving the wall closer to the building in order to maintain the 2ft spacing between
back of wall and the guardrail posts as specified in the detail is sheet S -4.
13. For the wall along the Right of Way of Rio Road please provide a specific section detail
dimensioning the length of the geogrid system and show how the geogrid is built around the
guardrail. Please also show the ROW line in the section detail.
14. The guardrail along Rio Road should be maintained by VDOT. The retaining wall along the
ROW may need to be maintained by VDOT. Ultimately, the decision regarding maintenance of
the guardrail and wall will be made by VDOT. The applicant should be made aware that the
ROW line could need to be shifted farther into the site.
15. All drainage pipes carrying water from the VDOT right of way must have drainage easements
dedicated to public use before the issuance of the first Certificate of Occupancy. The easements
dedicated to public use should be clearly differentiated from the other drainage easements shown
on the plan. The easements that must be dedicated to public use are over pipes 1, 2A, 2C, 3, 5, 7,
9, 11, 21, 23, 25, 27, 29, 31, and 33. Any portion of the drainage easements located on TMP 61-
184 must be recorded before site plan approval.
16. Please provide a note on the cover sheet below the sheet index stating that the ROW dedication,
public drainage easements, and RWSA easement must be recorded prior to the issuance of the first
Certificate of Occupancy.
17. Please remove all significant trees from the public drainage easements.
18. The entrance has a slope steeper than 4% on the exit from the site. Please reduce this slope to 4%
or flatter.
19. The speed limit on this section of Rio Road is 35mph. For this reason, the sight distance triangles
must be adjusted.
20. Please provide overland flow relief for inlets 12 and 16 so that structures will not be flooded in
case of inlet failure. [DM 18- 32.6.6.s]
21. Please show the crossing of a sewer lateral and fire line for drainage pipe 25.
22. In the calculations, a few of the pipes do not appear to be flowing under open channel flow
hydraulics. Please adjust the design of these pipes.
23. Please provide a channel design, with ditch lining, for the stream reconstruction after Pipe 3 is
placed.
24. The drainage area map doesn't match up with the design of the roofdrain system. Please update
the map and calculations accordingly.
25. Many of the drainage areas in the plan that are >90% pavement should have a time of
concentration of 5 minutes. For instance, drainage areas for inlets 32 and 26 should have a time of
concentration of 5 minutes. Please update the map and calculations accordingly.
B. SDP - 2010 -00013 Road Plan Comments
1. The barricade on Treesdale Way must be removed. Engineering review will not approve a plan for
this development that lacks safe movements from and onto northbound Rio Rd. In order to receive
engineering approval, Treesdale must either provide a full intersection on site (which may not be
allowed by Planning /Zoning because of the approved ZMA), construct the necessary road
improvements proposed in the Stonewater construction set, or wait until these improvements are
built or bonded by the Stonewater Developer before getting a Certificate of Occupancy. If the
applicant wishes to construct these improvements, the necessary road plans should be included in
this set and also accounted for in the Treesdale ESC plan. All necessary offsite easements and
ROW dedication must also be provided prior to site plan approval.
2. The applicant has labeled the travelways within the plan as private roads. In looking through the
preliminary site plan file, it appears that these travelways were not approved as private roads. In
order to be referred to as a private road, please provide a request per 14 -234. The private roads
can be authorized by the Chief of Current Development. The appropriate road standards can also
be determined by the Chief of Current Development if approval of the road is granted. A technical
review of the road plans will be performed by engineering once the roads are authorized and the
standards determined. This request is not needed if the applicant changes all references to "private
roads" to "private access easements." Private access easements will be reviewed to the standards
outlined in 18 -4.12 and these standards appear to be met as designed.
3. In the Treesdale Way section, one of the sidewalks should be specified as 6ft wide.
C. WPO- 2010 -00011 Stormwater Management Plan Comments
1. Per Water Protection Ordinance text amendments that were approved by the Board of Supervisors
last year, the WPO application for the Stonewater Development, WPO- 2007 - 00045, has been
voided because approval was given to the plans more than 12 months ago. Treesdale must include
all of the design graphics and calculations for the shared facility in this set for re- review. The
calculations should be updated with the latest proposed hydrologic information. (It looks as
though the drainage area to the BMP has gotten larger since the original design and the post -
development factored C calculation for Treesdale Park in the Stonewater set were incorrect.)
2. Please include a modified simple spreadsheet for the SWM facility.
3. Please specify the design of the concrete trash rack on the riser and provide a stage - discharge
graph so that routing calculations can be confirmed.
4. The pond shall not backwater into the drainage system. Please raise the outlet of the drainage
system to at least the permanent pool elevation.
5. Unless the design of the BMP is changing, please replace all references to an "enhanced biofilter
facility" to an "enhanced extended detention facility ".
6. Please provide a planting plan for the Extended Detention Facility.
7. New Stormwater Facility Maintenance Agreements will be needed for both parcels 61 -183 and 61-
184. The new agreements should refer to the " Treesdale Park SWM Plan (WPO-2010-0001 1)" on
page 1 of both documents.
8. A new SWM bond will be computed once the WPO plan is ready for approval.
D. WPO- 2010 -00011 Erosion and Sediment Control Plan Comments
1. Per Water Protection Ordinance text amendments that were approved by the Board of Supervisors
last year, the WPO application for the Stonewater Development, WPO- 2007 - 00045, has been
voided because approval was given to the plans more than 12 months ago. Treesdale must include
all of the design graphics and calculations for the shared facility in this set for re- review.
2. According to the existing contours, the diversion dike is going uphill in the northwest corner of the
site. The applicant has provided spot elevations but it is unclear how the grading is being
accomplished. Because the reliability of this diversion is critical to the success of the esc plan,
please show the grading and provide calculations for this diversion from the 422 contour to the
sediment basin. (Silt fence downhill of this diversion is not necessary.)
3. In the northeast corner of the site, please extend the diversion running east to west to the water
meter adjacent to Rio Road and provide a note stating that all runoff from the VDOT ditch is to be
rerouted with the diversion dike.
4. The drainage area to the sediment basin must be increased to account for VDOT ditch runoff south
of the development.
5. Please show the drip lines of all trees on each ESC sheet. Please also show the location of the tree
preservation area as approved by Planning in the latest variation on each sheet.
6. Please provide silt fence for the construction of the trail from the clubhouse to the Stonewater
greenway trail /maintenance road. (Please note the greenway and swm access path must be
included in this set.)
7. Please draw the 395 contour line in the basin if it was intended that it would be the bottom.
8. Please provide calculations for the dewatering orifice size. My calculations resulted in a diameter
of 3.5in which should not be rounded up to 4in.
9. There is a not a defined channel at the outlet of the 4.2 acre sediment basin. Discharging into this
area will likely cause rapid erosion. Please direct the outlet to an existing adequate channel or
attach a temporary slope drain to the barrel outlet and run overland until reaching the existing bed
of riprap within the stream channel.
10. The height of sediment trap 2 is taller than the maximum allowed per VESCH. Please redesign.
Considering comment #9, the outlet of the trap should be directed into the stream and not the tree
preservation area.
11. A USC symbol is needed at the pipe crossing of the intermittent stream.
12. Please provide the method use to calculate the intermediate volumes in the sediment basin when
confirming the wet and dry storage elevations. In both instances, my calculation with the stage
area table provided by the applicant indicates a higher elevation is needed for both the dewatering
orifice and top of riser.
13. The MS -19 calculations should be updated. The drainage area shown in the Stonewater set seems
to underestimate the total watershed to this channel. The topography in the vicinity shows the
drainage area including land north of the Waldorf School up to House # 770 on Rio Rd. Please
also be sure to use the 24 -hour storm as well as identify the n- value, permissible velocity and
computed velocity for each segment of each cross - section in the calculations (these are common
comments that adequate channel analyses receive). A site visit identified potential erosion at the
outlet of the facility (on the adjacent property —an easement may be needed to extend outlet
protection to stream) and eroded downstream side slopes.
14. An ESC bond will be computed once the WPO plan is ready for approval.
File: E1_fsp swm esc _PBC_wpo201000011- sdp201000013 Treesdale.doc