HomeMy WebLinkAboutSDP201000091 Review Comments Minor Amendment 2011-06-01ALg�,��
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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 - 00078; SDP - 2010 -00091
Plan preparer: Mr. Scott Collins, PE; Collins Engineering
Owner or rep.: Albemarle Housing Improvement Program, Inc.
Date received: (Rev. 1) 25 May 2011
3 December 2010
Date of Comment: (Rev. 1) 1 June 2011
17 January 2011
Engineer: Phil Custer
The first 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
i. riease 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.
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.)
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 SWMplan 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.
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.
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.
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 VSMH
3.02. Please update the routings accordingly.
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.
f. The two details showing the riser are inconsistent.
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.
h. The stormwater plan must consider the sidewalks associated with the private road and
Stonewater Drive.
i. 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 Ift of ponding). Considering
comment g and h, the required footprint is likely close to 5500sf). Please revise the
routings accordingly.
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.
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.
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. 1) 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. 1) 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.
D. WPO- 2010 -00078 Erosion and Sediment Control Plan Comments (Amendment to WPO -2010-
00011)
. Please modify the limits of disturbance so that all proposed work within the lines.
(Rev. 1) 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. 1) 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.
File: E2_mia esc swm _PBC_wpo201000078- sdp201000091 Treesdale Amendment.doc