HomeMy WebLinkAboutWPO200800063 Review Comments Stormwater Management Plan 2008-06-10ALg�,��
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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- 2008 - 00063, Oliva and Son Major WPO
Plan preparer: Mr. Tim Miller, PE (fax 434.979.1681)
Owner or rep.: Richard A Oliva and Sons (fax unknown)
Date received: 28 May 2008
Date of Comment: 10 June 2008
Engineer: Phil Custer
The WPO plan for the Olivia and Sons site has been reviewed. The following comments are provided.
A. WPO- 2008 -00063
1. The proposed disturbances are slightly under the 10,000sf threshold for the requirement of an
Erosion and Sediment control plan (I estimate the disturbances to be just under 9,500sf). If
disturbances are increased in later revisions to the plan or during construction, an Erosion and
Sediment control plan will be required. If the over 10,000sf violation occurs during construction
operations, a stop work order will be given until an ESC plan is approved. The owner should be
made aware of this risk now.
2. A requirement for adequate channel analyses is also provided for in the state stormwater
management law. Section 4VAC50 -60 -70 references the adequate channel requirement. An
analysis of the downstream pipe system will be required for this project.
3. The BMP spreadsheet indicates that a biofilter with a 65% removal rate is required but no sizing
calculations were provided. Please provide these calculations indicating that the bed area is 4% of
the impervious area draining to the facility.
4. All water quality facilities require sediment forebays for inflow points. The sediment forebays
should be sized for a 0.1" to 0.25" of the impervious area draining to them.
5. The county now requires that a mix meeting the "state approved standards" be placed in the
biofilter and not "Luck Bio- filter Mix." Please adjust the detail. [DM]
6. The soil media layer must be 2.5ft. [DM]
7. The gravel layer must be 1.5ft. [DM]
8. Please remove any reference to a sediment trap on the biofilter detail.
9. The perforated underdrain must be 6" in diameter. [DM]
10. The minimum diameter for pipes in stormwater facilities is 15 ".
11. Please provide an access path to the facility. [DM]
12. Please label the contours in the biofilter on the drawing.
13. Please show the underground electric line on the profile of the biofilter outlet pipe.
14. The planting ratio (shrubs to trees) should be between 2 to 1 and 3 to 1. Therefore, 2 trees (two
different species) and 6 shrubs (3 different species) will be required in this biofilter, though it
appears 8 plantings are more than enough for a biofilter of this size.
15. Three to one slopes are required in the biofilter. [DM]
16. Please provide Ift of freeboard during the 100 -year storm. [DM]
17. Please provide the county notes on the plan for "General Construction for SWM plans."
File: El swm PBC 08 -00063 Oliva and Sons