HomeMy WebLinkAboutWPO201300079 Review Comments Erosion Control Plan 2014-06-11� OF AL
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COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, Virginia 22902 -4596
Phone (434) 296 -5832 Fax (434) 972 -4126
Project: 5'h Street Station, phase 2
Plan preparer: Bohler Engineering, [dhines @bohlereng.com]
Owner or rep.: New Era Properties [alan.taylor @redlightmanagement.com]
Plan received date: original: 17 Dec 2013
Rev. 1: 22 May 2014
Date of comments: original: 21 Jan 2014
Rev. 1: 11 June 2014
Reviewer: Glenn Brooks
A. Erosion and Sediment Control (WP0201300079)
Rev.]: Current comments;
1. The large black lines on all the sheets obscure the plan details and lines for control measures. I find
this plan almost illegible because of this. Please correct.
2. It is not clear what is being constructed with this plan. All the road improvements are shown as
complete. Therefore, this plan could not be permitted until after the road is constructed.
3. Provide sediment trapping measures. Fencing is not sufficient.
4. Provide protection for wall construction. There is not enough protection for Moores Creek and the
wall construction.
5. SSF and double X lines are not state approved symbols or standards, and this plan has no variances.
6. Fencing is shown over rip -rap and concentrated discharges, which is not acceptable.
7. Clarify how this plan fits in with other erosion and sediment control plans, mitigation plans, and
stormwater plans.
8. Adequate channels narrative on sheet 7 is referencing an out -of -date design manual. We must follow
"9VAC25- 870 -66 Water quantity ".
Original comments, given on the abbreviated review form;
1. No adequate limits and perimeter measures out of work areas. (Stream area must be protected below
walls. Not clear how this happens.)
2. All stages of construction not adequately protected. SF not adequate as a sole protection.
3. Adequate channels not addressed.
4. This plan shows only limits and fence. There do not appear to be any sediment trapping measures
shown.
5. There is not enough protection for Moores Creek and the wall construction.
6. This plan does not match the stormwater plan.
B. Stormwater Management Plan (WP0201300079)
Original comments, given on the abbreviated review form. Revised comments are preceded by "Rev. 1: "
Engineering Review Comments
Page 2 of 3
1. There is not enough detention storage for on -site areas.
Rev. 1: This was not checked with this revision.
2. System A +B areas should assume forested conditions prior to development. The previous
clearing was an unfinished project.
Rev. 1: The BMP computations are still unresolved. It is safe to say the removal rate is above
75% for each on -site drainage area. The 47 acres on the computation provided was not found
on a drainage area map. The on -site areas and treatment appears to be for three or four
separate drainage areas and discharges that do not add up to this. A removal rate could be
provided for each discharge point, and each facility result compared to the targets. This might
indicate that future development on Avon may need its own site treatment in future. Areas
like floodplains and buffers, which are not developed, are not part of the project disturbed or
developed area, and should not be included in treatment area computations.
3. All facilities, incl. level spreader, need maintenance access
Rev. 1: not addressed.
4. These are non - standard sand filters. Use state approved standards, or provide DEQ approval
for these systems at the desired removal effeciency. Demonstrate WQV is captured in filters.
Demonstrate extended detention will not inundate filters. There is currently no way to replace
for rust, or easily inspect or clean, or replace media. Design for these and provide structural
certifications.
Rev. 1: The sand filters are not a state standard. The DC Sand Filter referenced (VSMH 3) is
limited to 1.25 acres. For larger areas you would need to use a different, separate vault placed
in the drainage system closer to the inlets where drainage areas to each vault could be limited
to 1.25 acres. That said, if you can produce a copy of approval from DEQ for this system, we
would proceed with that approval, and review the details of the system setup.
5. The in- stream flow splitter is a clogging problem and the pond may be below the water table.
I just don't see this as approvable at all. Per the zoning, build a in -line pond upstream of the
culvert and pay the Army Corps fees necessary for disturbance, or request a variance /ZMA.
Rev. 1: This has been addressed by removal of this system.
6. Provide DEQ approval for the landfill pond.
Rev. 1: not addressed.
7. Provide scaled sections and profiles through facilities. Manufacturer's generic drawings are
not adequate.
Rev. 1: Scaled drawings have been provided. If the filter can be approved by DEQ, some
details in need of addressing;
a. The end pipes appear to allow bypass of the filters
b. Filling the bmp manhole with stone prevents maintenance access to outlets.
c. There is no practical way of cleaning these giant vaults. It appears an Austin surface
filter is more appropriate for this size, allowing machine access for maintenance.
d. Groundwater data is required before approval. A wet sand filter may become
anaerobic. Even if groundwater can be lowered, it is not clear a filter this size
underground will ever dry out sufficiently to be effective.
e. Credit cannot be given for water quality in extended detention if it follows the filters.
Extended detention with no biological component is simply a settling chamber, and
Engineering Review Comments
Page 3 of 3
this has likely already occurred sufficiently in the prior treatment. Place any
detention before the filters.
8. The plans are too big for storage in county files. Please separate all the computations into a
sealed package. Clarify all storage volumes used and assumptions and sizing, and outlet
structures, after revised hydrology per above. There were not enough plan details to verify
computations for structure
Rev. 1: partially addressed. There are still narratives and computations in the plan sheets.
File: E2_ phase2_ esc, swm_GEB_5thStrStationPhase2.doc