HomeMy WebLinkAboutWPO201500062 Approval - County Minor Amendment 2016-03-31 Twr
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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
VSMP Permit plan review —Approved
Project: Glenmore Leake K2 Lots 24-27&29 Amendment Plan
Plan preparer: Graham Murray,Collins Engineering[200 Garrett St.,Suite K,Charlottesville,
VA 22902,graham(aeollins-engineering.com,Scott@collins-engineering.com]
Owner or rep.: Neal Sansovich,Central Virginia Real Estate Ventures LLC
2325 Grey Heron Rd,Keswick,VA 22947
Plan received date: 27 Aug 2015
(Rev. 1) 20 Jan 2016
(Rev.2) 31 Mar 2016(.PDFIe-review)
Date of comments: 24 Sep 2015
(Rev. 1) 6 Mar 2016
(Rev.2) 31 Mar 2016—Approved
Reviewer: John Anderson
A. Stormwater Pollution Prevention Plan(SWPPP)
The SWPPP content requirements can be found in County Code section 17-405. A SWPPP must contain(1)
a PPP,(2)an ESCP,(3)a SWMP,and(4)any TMDL measures necessary.
1. Provide SWPPP Exhibit. May use details from WP0201300015 ESC plan, if relevant. A SWPPP
is not requested,but rather Exhibit showing PPP measures. PE-seal(signature/date)is required:
Alternatively,provide a complete SWPPP: Note: A SWPPP has been required by the Virginia
VPDES permit program for projects disturbing an acre or more since 2009,at least. Request
solicits material that should exist for WP0201300015,but 1 regret late request for an Exhibit.
(Rev.2)Addressed.
B. VSMP:SWPPP: Stormwater Management Plan(WP0201500062/Amends WPO201300015)
VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This
plan is approved.
1. Identify WPO Plan Number and Title being amended, Revise Title,sheet I,to include WPO Plan number
and title being amended. (Rev. 1)Addressed.
Remaining comments,sheet 2:
2. Provide SWM Facility Access. (ACDSM.5.BMP for SWM) (Rev.1)Partially Addressed. As follow-up:
Ref photos 1,2(county;9/24/151:Access/guardrail conflict. Provide opening. Reference/adopt VDOT
guardrail specifications in design(GR 2,2A). Show guardrail in both plan view itnages,sheet 2.
Nips/
Engineering Review Comments
Page 2 of 3
Photo 1/view south Farringdon Rd.
(removed--shown with prior comments)
Photo 2/view north--Farringdon Rd.
(removed-ref prior comments)
' ,ardrail details+'design.IVDOT R&B Spec/Vol. 1 -GR-2,2A:sheets 1 and 2:rev.date 7/111
(Rev.2)Addressed.
3. Label road(provide name). (Rev. 1)Addressed.
4. Furnish Approved basin 2-, 10-, 100-yr routings for comparison. (Rev.1)Addressed. Asfollow-up:
WP0201300015:(Apr 17,2013 routings/peak cfs)
Q2==17.07
Qum=64:02
WP0201500062%Amendment(peak cfs): •
Q2=7.59,ok,<Apr 17 2013 routings
Qio=42.83
Qwo=76.70
WP0201500062 Qio>WP02013000.15 Q10. DEQ has advised that a Part IIC facility that proposes to
increase rate of discharge forfeits Part IIC eligibility,writing:"Your summary of our telephone conversation
(below)is correct. "Grandfathered"projects that are subsequently amended or modified resulting in an
increase in the amount of TP leaving each point of discharge,or resulting in an increase in the volume or
rate of runoff are no longer considered"grandfathered under Section 48 of the VSMP regulations. As a
result,the amended or modified project must be designed to comply with the new Part 1113 technical criteria.
[Andrew Hammond,VDEQ email: 12,15/2015.5:42 P1511
Please revise design to prom iiia Q,,,<Apr 17, 2013 (' (Rev.2)Follow-up Addressed.
Routing Pethod: storage-indication
Hydrograph 0
Routing summary of Peaks: 2-yr 24-hr Peak sc5 storm
inflow (cfs) 23.062 at 11.98 (hrs))
discharge (cfs) 15.919 at 12.10 (hrs)
water level (ft) 348.951 at 12.10 (hrs)
storage (cy) 738.266
Hydrograph 1
Routing suwmary of Peaks: 10-yr 24-hr Peak 5(5 storm
inflow (cfs) 9 at 11.98 ((Ms))
discharge (cfs) t 12.14 (hrs3
water level (ft) 351. at 12.14 CCtrs
storage (cy) 1427.689
Hydrograph 2
Routing summary of Peaks: 100-yr 24-hr Peak SCS storm
inflow (cfs 100.505 at 11.98 (Ius)
discharge (cfs 81.120 at 12.06 hrs
water level (ft 353.332 at 12.06 (hrs)
storage (cy 2112.510
5. Identify Approved basin type consistent with 9VAC25-870-96.C. Table 1,or DEQ BMP Clearinghouse
nomenclature(basin is non-specific). (Rev. 1)Addressed.
6. Multiple references to As-built are inconsistent with site inspection,24-Sep 2015(discussed briefly with
Scott,24-Sep). Correct existing grade to reflect As-built grades. In places,grade is 1:4,near vertical
Steepest existing rade on WPO Plan Amendment is 1:1. Accuracy is critical Avoid inaccurate grades
which may have contributed to conditions that required this plan amendment. (Rev. 1)Addressed
Appreciate response:"Tile extended detention basin's topography and spot shots shown reflect asbuilt data
provided to Collins Engineering by Commonwealth Land Surveying, LLC. The September 24,2015
comments reference a site visit where County Engineering observed grades of 1`4 This is in contrast to the
licensed land surveyor's topography which triangulates grades of I:1:33 in the vicinity of the basin's steeper
areas. In both cases though,the steeper grades to the east are mitigated with the proposed grading
modifications. The proposed grading changes consist of filling the lower 6' and shrinking the bottom
footprint's length slightly. To offset this minor shortening of the basin floor,it was expanded in width.
Raising the facility 6'now allows the contractor to catch grade more easily while burying steep side slopes.
Shrinking the footprint's length also allows the contractor to grade back to the 350'contour from the new
basin floor elevation of 342'over a greater horizontal length. It is the applicant's hope that the paid 3rd
Engineering Review Comments
Page 3 of 3
party survey,coupled with the proposed modifications,resolves County Engineering's concerns regarding
the proposed side slopes of the extended detention basin." [Last pp.:24-Sep 2015 site photos]
7. Specify means of sealing existing low-flow orifice,and three 12 DIA mid-flow orifices: This requires
engineering,not flexibility. Specify materials;products,etc. Specify with level of detail to ensure orifices
are watertight. Alternatively,specify which sections of existing 42"DIA concrete riser must be replaced.
(Rev. 1)Addressed.
8. Revise profile description to be sealed.' Revise to reference details,narrative,notes,specifications. See
item#7. (Rev. 1)Addressed:
9. Delete reference to `Equivalent trash rack'(Hanson typical,bottom margin); `Contractor may elect to install
a different trash rack.' Design cannot leave this degree of unapproved plan change to a contractor's
discretion. (Rev.1)Addressed.
10. Specify Hanson Anti-vortex frame and grate. Grate access to 42"DIA riser is essential. Design must
specify precast Hanson Anti-vortex device with frame and grate,or alternative device: (Rev. 1)Addressed.
11. Provide field survey As-built Exhibit(not just spot shots)to accompany Plan Amendment,an exhibit based
on field survey data obtained after today. (Rev. 1)Addressed.
12. Note: A number of photos support comments,and are available. [pp. following] (Rev.2)Acknowledged.
C. VSMP: SWPPP: Erosion Control Plan(WPO201500062)
Virginia Code§62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan is approved.
Provide Exhibit that provides ESC measure details including storm runoff bypass/diversion during period of
constructed modifications to facility. This is not request for a complete ESCP,but is essentially equivalent.
Required for SWM Plan Amendment Approval. Focus on practical measures and potential for downstream
impact since hipass of storm events during period,of construction would appear essential May revive
WPO201300015 ESC plan sheet's to show ESC measures, if helpful. (Rev.2)Addressed.
Please submit four(4)copies of the WPONSMP plan for Approval. Please also provide 2 copies of SWPPP
exhibit,and 2 copies of revised ESCPNSMP SWPPP inserts(11"x 8.5").
Thank you.
COLLINS 21tgARRETT ST, SUITE K CHARLOTTESVILLE VA 22902
434.293.3719 PH 434.293.2813 FX
www.collins-engineering.com
John Anderson,P.E.
Community Development
County of Albemarle
401 McIntire Road,Room 227
Charlottesville,VA 22902
RE:Glenmore Leake K2 Lots 24-27&29 SWM Amendment(WPO 201500062)
Thank you for your comments on the project referenced above.Please let this letter supplement the revised plans in response to your
comments dated March 6,2016.
A. Stormwater Pollution Prevention Plan
1. A stormwater pollution prevention plan exhibit has been provided with this submittal.
B. Stormwater Pollution Prevention Plan
2. The plans have been revised to show an opening in the guardrail to allow construction and stormwater management access.The location
of the opening was strategically located at an embankment and VDOT standards and specifications have been added to the plans
mandating construction adhere to these requirements.Also,the plans have been revised to show the existing locations of guardrail.
4. The previous plans called for the new installation of a 12"orifice.The revised plans now call for the installation of three new 12"orifices.
The orifice inverts are proposed at the same elevation,so the 30 hour low-flow drawdown water quality orifice calculations previously
approved are not impacted.The addition of the orifices only impacts hydraulically the storm events that crest above the elevation 346.63'
(the invert of the 12"orifices).The result is a 2-and 10-year peak outflow below the previously approved flows.Hereby adhering to
County Engineering's direction.Additionally,the revised routing calculations attached provide the minimum 2'of freeboard.
12. This is comment is acknowledged.
C. SWPPP-Erosion Control Plan Exhibit
1. An 11"x17"erosion and sediment control exhibit has been provided with this submittal,outlining an acceptable method for the
modifications to the basin.
If you have any questions regarding the proposed plans please do not hesitate to contact me.
Sincerely,
Graham Murray,PE