HomeMy WebLinkAboutWPO201900068 Correspondence 2020-06-24 (2)608 Preston Avenue
P 434.295.5624
T I M M O N S GROUP Suite 200 F 434.295.1800
Charlottesville, VA 22903 www.timmons.com
June 24, 2020
John Anderson
County of Albemarle
Dept. of Community Development
401 McIntire Rd, Rm 227
Charlottesville, VA 22902
RE: Red Hill ES — VSMP Plan Review — WP02019-00068 - Comment Response Letter
Dear Mr. Anderson:
We have reviewed all of your comments from March 26, 2020 and made the necessary
revisions. Please find our responses to the comments below in bold lettering.
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. This SWPPP
is disapproved, and the reasons are provided in the comments below.
1. Section, 1 Registration Statement / Sec. V.C.: Check 'No, ' unless land disturbance has
commenced.
Registration statement has been revised accordingly.
Rev. 1: Comment addressed.
2. Section 1, Registration Statement / Pg. 4: Sign/Date.
The registration statement will be signed by the contractor as soon as one has been chosen.
Rev. 1: Comment persists.
The registration statement has been signed and included in the SWPPP.
3. Section 6.A. / Exhibit (p. 21-22, .PDF):Indicate initial location of rain gauge.
Rain gauge has been added to PPP phase 1
Rev. 1: Addressed.
4. Section 6.A / Exhibit (p. 21-22, .PDF): Revise LOD: SWPPP Exhibit + SWM / ESC inserts +
VSMP/WPO Plan. 0.94 Ac. As shown is unrealistic, and includes isolated areas without
connection to CE, or material storage / laydown (unless access is through Ex. Building).
Assume areas crossed with equipment during construction are disturbed by virtue of
compaction or end -of -project typical need to till/amend soil, clear debris, restore, or
install temporary / permanent stabilization. Ref. isolated areas of proposed LOD, image,
ENGINEERING I DESIGN I TECHNOLOGY
below. Again, disturbance will likely exceed proposed limits as a practical matter.
Engineering questions need for limiting LOD<1 Ac. There is no appreciable delay when
applying for a DEQ VPDES VAR10 permit, and no additional requirements since LOD>
1Ac.
LOD has been revised and is now connected throughout the site.
Rev. 1: Addressed.
5. Section 6.A. / Exhibit (p. 21-22, .PDF): Indicate initial location of temporary solvent
/chemical storage (temporary material storage trailer).
Temporary material storage trailer has been added to phase 1 of the PPP
Rev. 1: Addressed.
6. Section 7, Impaired Waters: Revise proposed enhanced inspection frequency (item(2))
consistent with VAR10, Part II G 2.a.(2.) (Ref. pg. 13 / VAR10).
Acknowledged
Rev. 1: Addressed.
7. Section 7: Furnish missing (TMDL/impaired) data for North Fork Hardware River, since
designated for enhanced inspection.
TMDL report is now included in section 7 of the SWPPP Report.
Rev. 1: Addressed.
8. Section 9, Signed Certification: Sign -date.
Section 9 will be completed when a contractor has been selected.
Rev. 1: Comment persists. Note: Albemarle cannot register this project with DEQ or schedule a
preconstruction meeting until the project is registered with DEQ.
Section 9 has been signed and included in the final SWPPP.
9. Section 12: Revise proposed enhanced inspection frequency (item (2)). Also, item 6.,
above.
Section 12 has been revised accordingly.
Rev. 1: Addressed.
10. Section 1, Registration Statement, p.2, Sec. IV, E- MS4: Leave blank since project does
not discharge to Albemarle County MS4. See County GIS/MAP Themes
(Layer)/Utilities/Water-Wastewater-Stormwater/Albemarle County MS4 boundary. Red
Hill is well outside/south of Albemarle County MS4 boundary.
Registration Statement has been revised accordingly.
Rev. 1: Addressed.
11. Revise SWPPP title to include reference to WPO201900068
SWPPP title has been revised to include WPO number
Rev. 1: Addressed.
B. Stormwater Management Plan (SWMP)
VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a
SWMP. This plan is approved pending purchase of 0.50 lb. phosphorus nutrient credits.
1. Revise title to: Red Hill Elementary School Additions and Renovations VSMP
WP0201900068. Please QC: do not submit plan titled Site Plan, or Site Plan Amendment
as a VSMP/WPO Plan.
Cover sheet has been revised accordingly.
Rev. 1: Addressed.
2. C2.0: Revise to show TMP 08700-00-00-060BO (Thomas Brendt) since design proposes to
release runoff to a LS, then a slope leading to this property, rather than a defined
channel. Show residence at 3947 Red Hill School Road. Show property boundaries
consistent with GIS. Label TMP# 08700-00-00-060B0. (County GIS, image, below)
The LS location has been revised to direct stormwater into the existing roadside ditch. See
Sheet C5.0.
Rev. 1: Withdrawn.
3. C6.0: Water quality calculations/surplus removal: Plan proposes to utilize 0.44 lb.
surplus phosphorus from Scottsville Elementary School Additions project (0.44 lb. of
0.44 lb. total); plan also proposes to use 0.06 of 0.15 lb. surplus phosphorus from
Woodbrook Elementary School project to meet Red Hill projects 0.50 lb. TP Load
Reduction requirement. This works only if Woodbrook and Scottsville Elementary are
located in the same HUC or upstream HUC (see, below), and Woodbrook and Scottsville
schools are not in the same HUC or upstream HUC. Revise WQ compliance plan. (Ref.
images/link, below. Also: Scottville — WP0201900051; Woodbrook — WP0201600074):
9VAC25-870-69A./ Offsite Compliance Options (5): '5. When an operator has additional
properties available within the same HUC or upstream HUC that the land -disturbing
activity directly discharges to or within the same watershed as determined by the VSMP
authority, offsite stormwater management facilities on those properties be utilized to
meet the required phosphorus nutrient reductions from the land -disturbing activity.'
9VAC25-870-10/Definitions: "Hydrologic Unit Code" or "HUC" means a watershed unit
established in the most recent version of Virginia's 6t" Order National Watershed
Boundary Dataset unless specifically identified as another order.'
Stormwater quality calculations have been revised. Ownership to purchase nutrient credits to
satisfy quality requirements.
Rev. 1: Addressed.
C5.0:
4. Post -developed runoff may not release to undefined channel so close to a neighboring
residential property. Revise design.
Post -developed run-off has been redesigned to out flow to existing channel parallel with road.
Rev. 1: Addressed.
5. Str. 100 / outfall: Evaluate effect of existing impervious runoff on existing channel along
Red Hill School Road. Evaluate 10-year event, whether Ex. Roadside ditch has adequate
capacity, and whether ditch flow bypasses driveway entrance to 3947 Red Hill School
Road to reach tributary to South Branch.
The existing ditch has been analyzed for the 10-year event. See detail "Road Side Ditch
Calculation" on Sheet C6.0
Rev. 1: Addressed.
6. LS in this location is problematic. Ref. 9VAC25-870-66.D., which cautions against
downslope effects. Also, item 4., above. LS releases to featureless slope toward 3947
Red Hill School Road (Brendt property).
The LS has been relocated to prevent downslope effects to 3947 Red Hill School Road
property.
Rev. 1: Addressed.
9VAC25-870-66.D.
D. Increased volumes of sheet flow resulting from pervious or disconnected impervious
areas, or from physical spreading of concentrated flow through level spreaders, must be
identified and evaluated for potential impacts on down -gradient properties or resources.
Increased volumes of sheet flow that will cause or contribute to erosion, sedimentation, or
flooding of down gradient properties or resources shall be diverted to a stormwater
management facility or a stormwater conveyance system that conveys the runoff without
causing down -gradient erosion, sedimentation, or flooding. If al runoff from the site is sheet
flow and the conditions of this subsection are met, no further water quantity controls are
required.
7. C5.2, C6.0: Consider effect of relocated (impervious) modular trailers on post -developed
ground cover. Analyze trail DA (C5.2). Show trailer leader line outfalls. Adjust post -
redeveloped ground cover (C6.0).
Per changes in direction, ownership will provide one (1) trailer to be located over the existing
asphalt pavement. Trailer is temporary and will not create disturbance to the asphalt surface.
Rev. 1: Addressed.
8. C7.0: Provide Std. VDOT MH with STR206-STR200 profile. Nyloplast does not meet
Drainage Plan checklist, ACDSM, or VDOT drainage manual guidance. Nyloplast is
appropriate only for yard grates, or limited conveyance over limited distance. Use Std.
VDOT MH Str. With 12" RCP storm pipe.
Nyloplast basins have been changed to VDOT standard structures as requested.
Rev. 1: Addressed.
9. C7.0: Str 218 — 214: Revise 4" storm line to 6" Min.
Storm has been re -designed. All storm line is a minimum 6".
Rev. 1: Addressed.
10. Remove sheet C0.4, Site Plan Photometrics.
Sheet has been removed from Plan set.
Rev. 1: Addressed.
C. Erosion and Sediment Control Plan (ESCP)
Virginia Code 62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP.
This plan is disapproved for minor reasons listed at items 6 and 11, below. The erosion control
plan content requirements can be found in County Code Section 17-402.
1. C3.1: Include ACDSM paved construction entrance detail.
Detail is not included on sheet C3.1
Rev. 1: Addressed.
2. C3.2, C3.3: Revise LOD. Also, SWPPP comment, item 4., above.
LOD has been revised accordingly.
Rev. 1: Addressed.
3. C3.3, C3.4: Label mulched areas, trails, etc. (blue arrows below). Confirm whether trails
or play areas are to be constructed on existing grade, with no disturbance, whatsoever
(i.e. outside LOD). Label circular features shown below.
The LOD has been revised to incorporate the mulched areas, trails, etc.
Rev. 1: Addressed.
C3.2:
4. Label ST floor dimensions.
Sediment trap floor dimensions have been added.
Rev. 1: Addressed.
5. Provide break in SF at ST stone weir (outfall).
Silt fence has been broken at stone weir outfall
Rev. 1: Addressed.
6. Revise CE label to PCE (paved construction entrance).
Label has been revised to PCE
Rev. 1: Not addressed.
The construction entrance label on sheet C3.2 have been revised to "PCE"
7. Revise ST L: W ratio to more nearly resemble (VESCH Std. & Spec. 3.13) 2:1 length -width
ratio.
The current dimension of the ST is 66.1x10.1 which exceeds the minimum 2:1 length -width
requirement. The stone weir has been shifted to allow for a longer flow path throughout the
sediment trap.
Rev. 1: Addressed.
8. C3.3: Provide labels to identify five circular areas material surface type. Show proposed
grading for level circular areas, if areas are to be level. If grading is required, revise LOD
/ VaRRm.xls. Also, see SWPPP item 4., ESCP item 3., above.
The five circular areas shall consist of concrete. Proposed grades have been shown as
requested on C5.0.
Rev. 1: Addressed.
9. C3.2, C3.3: Show PS, MU for five circular area, within areas of land disturbance, or
grading.
The five circular areas shall consist of concrete and will not require PS or MU stabilization.
Rev. 1: Addressed.
10. C.S: Show grading required to level pads for relocated modular trailers, an activity
included with this project (Note Ex. Contours: 723, 722, 721). Revise LOD.
Per changes in direction, ownership will provide one (1) trailer to be located over the existing
asphalt pavement. Trailer is temporary and will not create disturbance to the asphalt surface.
Rev. 1: Addressed.
11. C6.0 Riprap channel detail: It is unclear whether this detail defines C3.3 ESC feature, or
permanent feature. Please clarify.
The riprap channel detail located on C6.0 will be a permanent feature.
Rev. 1: Partially addressed. As a follow-up: Please revise detail caption, C6.0, to include
descriptor permanent.
The riprap channel detail on sheet C6.0 has been revised to call the riprap channel permanent.
D. Pollution Prevention Plan (PPP) Ref. SWPPP, Sec. A, items 3, 4, 5, above. Rev. 1: Addressed.
The PPP content requirements can be found in County Code section 17-404. PPP is approved.
We have included PDF copies of the plans and calculations for your review. If you have any
questions or comments, please feel free to give me a call at 434.295.5624.
Sincerely,
Andrew Allison, PE
Project Engineer