HomeMy WebLinkAboutWPO201000025 Review Comments Stormwater Management Plan 2010-05-28ALg�,��
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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: WPO- 2010 - 00025, Comfort Suites Inn at Hollymead Town Center
Plan preparer: Mr. Malachi Mills, PE; Rummel, Klepper, & Kahl, LLP
Owner or rep.:
Date received:
Date of Comment:
Engineer:
HTC Hotel LLC
15 April 2010
28 May 2010
Phil Custer
The ESC and SWM plans for Comfort Suites Inn at Hollymead Town Center, received on 15 April 2010,
have been reviewed. Comments from the review of the site plan submittal will be provided in a separate
comment letter at a later date. The ESC and SWM plans cannot be approved as submitted and will require
the following corrections before approval can be granted:
A. Stormwater Management Review Comments
1. The majority of this site appears to have been accounted for in the downstream pond during its
design (though please see the following comment). However, in order to use the water quality and
detention credits, please provide a letter, agreement, or recorded document from the owner of TMP
32 -41133 that authorizes the use of the SWM facility by TMP 32 -41135.
2. This plan must match the previously submitted site plan for the pond parcel, SDP - 2008 - 00106, in
the area of the southern forebay.
3. Please provide clarification of the as -built survey of the offsite pond. The plan shows a water
elevation of 521.1 but an invert elevation of 520 (original design). Also, the top of the facility is
called out as 526.94 but original design called for a crest elevation of 525.50. The rectangular
weirs are 2" higher than the original design. Depending on the responses to the first two issues,
the pond design file and routing may need to be updated to match what was originally constructed.
4. The top of grass elevation is mislabeled in both of the green alley details.
5. The green alley calculations on sheet 15 of 16 appear to overestimate the volume of the facility.
Using a planimeter, I found the volumes of Green Alley A and B to be 843cf and 756,
respectively.
6. We are unfamiliar with the current Green Alley design with the Green Tech pallets. A quick
internet search did not yield any more helpful information. The proposed cross section should be
replaced with the widely accepted bioiilter design with 2.5 of bioiilter mix above 12 " -18" of
gravel with a perforated underdrain directed into the inlet structure. The biofilters must be planted
with trees and shrubs per the recommendations of the VSMH: 1 planting per 100sf; a shrub to tree
ratio between 2:1 and 3:1; and, at least three varieties of both trees and shrubs, if possible.
7. There are slopes steeper than 2:1 within "Green Alley B ". Please revise the grading keeping in
mind that the steepest slope allowed in the county is 2:1 and that any slope steeper than 3:1 must
be planted with a low maintenance, non - grassed groundcover. To treat drainage from the parking
dropoff area, please remove the curbing on the northwest side of the green alley and provide stone
on the slope to the bed of the facility. Also, to provide more room in the biofilter, I recommend
removing the curbing on the southeast side of the island.
8. A Stormwater Facility Maintenance Agreement must be recorded for the parcel because of the
smaller green alleys /rain gardens/biofilters (instructions). The agreement must reference the
current application title and number (WPO- 2010 - 00025).
9. A SWM bond will be computed at the time of WPO plan approval.
B. Erosion and Sediment Control Review Comments
1. This site drains to the existing sediment basin at the corner of Timberwood Blvd. and Route 29.
However, in order to use the facility as the primary sediment control measure, please provide the
county with a letter, agreement, or recorded document from the owner of TMP 32 -41D# that
authorizes the use of the facility by 32 -41D5. The owner of the facility will be required to
maintain the bonds until all developments within the watersheds are stabilized.
2. All offsite construction easements are needed before the plan can be approved.
3. Please make the existing contour lines and labels darker. It is difficult to see which direction water
is flowing and make sure all contours are tied in appropriately. I am most interested in the grading
at the western corner of the property where the temporary road will be constructed and the
perimeter of the existing SWM facility.
4. In phase I, please extend the diversion to the property line of the Target parcel assuring positive
drainage over the diversion.
5. In phase II, please provide a ROW diversion at the southern entrance directing water into the ditch
southeast of the pavement. I do not think silt fence across the pavement is realistic.
6. I do not see the Tree Protection fencing referenced in the construction sequence. I recommend
providing some safety fencing at the limits of disturbance adjacent to the existing Target parking
lots, Connor Drive, and Timberwood Blvd. This is not a requirement.
7. Please provide Dust Control symbols through the site in both phases.
8. Please provide Permanent Seeding symbols in Phase II throughout the site where applicable.
9. Show outlet protection stone and symbol at the outlets of all drainage pipes.
10. In the soil note, please reference the previously approved mass grading plan and mention the
possible indiscernible nature of the soil existing onsite now because of the earlier grading.
11. An ESC bond will be computed by the county at the time of WPO plan approval. The itemized
table on sheet 4 of 16 is helpful, but the unit prices differ from the county's bond computation.
The cost - estimate half of this table may be removed.
File: E1_esc swm_PBC _ wpo- 2010 -00025 Comfort Inn- HTC.doc