HomeMy WebLinkAboutWPO202200001 Correspondence 2022-04-14p' Draper Aden Associates
/%V Engineering • Surveying • Environmental Services
110 Avon Street
Charlottesville, VA22902
434.295.0700
www.daa.com
April 14, 2022
David James
Engineer
County of Albemarle
Department of Community Development
401 McIntire Road, North Wing
Charlottesville, VA 22902-4596
RE: Southern Albemarle Convenience Center — WP0202200001
Draper Aden Associates Project No. 2200656
Dear David:
The enclosed copies of the WPO submittal documents for the Southern Albemarle Convenience Center
were revised to reflect your comments dated February 17, 2022. We offer the following responses
(shown in bold) to your comments.
Stormwater Pollution Prevention Plan (SWPPP)
Registration Statement:
a. Please complete section I operator/permittee information.
Response: This will be completed by contractor prior to WPO approval.
b. Fix spelling error for project name under section II.
Response: Corrected.
c. Sign & date form prior to permit issuance.
Response: This will be completed by contractor prior to issuing permit.
2. Complete Section 4&5: Insert reduced sized copies of the approved ESC & SWM plans.
Response: Reduced sized copies of the plans will be included into the overall SWPPP
template once all plan comments are satisfied, prior to overall WPO approval.
3. Complete Section 2 prior to grading permit issuance.
Response: Noted.
4. Complete Section 6 prior to grading permit issuance.
Response: Noted.
Blacksburg • Charlottesville • Manassas • Newport News • Richmond • Virginia Beach • Raleigh
David lames
April 14, 2022
Page 2 of 5
5. Complete Section 9 prior to approval.
Response: Noted.
6. Complete Section 8 & 10 prior to grading permit issuance.
Response: Section 8 is completed. Section 10 will be completed prior to permit.
Pollution Prevention Plan (PPP)
1. Provide a PPP exhibit sheet showing controls in place prior to plan approval.
Response: Noted. This will be provided once all plan comments are satisfied, but prior to
overall WPO approval.
Stormwater Management Plan (SWMP)
1. Sheet C5: Label 'Conserved Open Space' area as 'SWM Forest and Open Space' Easement.
a. Show amount (acres).
Response: Notes updated on sheet CS.O and acreage added.
2. Include note on the cover: "The SWM Forest and Open Space Easement is subject to the
guidance set forth by DEQ in the Virginia Stormwater Management Program. The areas will
remain undisturbed in a natural, vegetated state, except for activities as approved by the local
program authority, such as forest management, control of invasive species, replanting and
revegetating, passive recreation (e.g., trails), and limited bush hogging to maintain desired
vegetative community (but no more than four times a year)."
Response: Note added to sheet CO.0.
3. Show SWM narrative (summary) addressing water quality/quantity (Part 11B) on the plans.
Response: A summary is shown on sheet CO.2. References to the regulation section have
been included as per our phone call on 3/7/22.
4. Ensure bioretention meets all requirements per DEQ specifications:
https://swbm pvwrrc.wp.prod.es.cloud.vt.edu/wp-content/uploads/2017/11 /BM PSpec-No-
9_BIORETENTION_v1-9_03012011.pdf
Response: The bioretention has been updated to match 2011 standards from the
previously referenced 2013 standards.
5. Specifically, please do the following for Bioretention 1 (w/underdrain):
a. Ensure 2-ft minimum bottom to bedrock separation.
Response: Confirmed by geotechnical report.
b. Ensure 2-ft minimum bottom to seasonal high water table separation.
Response: Confirmed by geotechnical report.
David lames
April 14, 2022
Page 3 of 5
c. Filter media: Please go with the 2011 standards on recommended bioretention soil mix
composition. We have found that higher % of fines (clay content) have caused issues
with water filtrating though.
Response: Media changed to 2011 version.
d. Filter media: Ensure an infiltration rate of 2 in/hr (min). Test will be required prior to
project termination.
Response: Note added under bioretention specifications on sheet C6.2.
e. Provide a trash rack for 3" orifice.
Response: A trash rack has been called for on the orifice on sheet C6.2.
f. Observation well should be above and tied to underdrain (C4).
Response: Observation well moved so that it is connected to the underdrain.
g. Provide impermeable liner since this project is considered a Hotspot Land use (solid
waste disposal).
Response: This use will not be considered a Hotspot Land Use as per your email on
3/15/22 so no liner is required.
6. Show level contour elevation along gravel diaphragm to ensure sheet flow from it. Drop can be
2-4-in minimum (C4, C6.1).
Response: Grading plan updated to provide more consistent elevations across the gravel
diaphragm. Detail on C6.1 updated to reference a 2"-4" drop.
7. SWM Calc. Packet:
a. Correct (should be 'Post') on page 14 of 16
Response: Chart in report update.
Erosion and Sediment Control Plan (ESCP)
1. Cover: Show'WPO202200001' under or near title.
Response: WPO202200001 added to C0.0.
2. Remove sheets C3.1, C3.2 from the WPO plan.
Response: Sheets C3.1 and C3.2 removed from WPO set.
3. Sheet Cl: We require topographic data to be field verified by the designer within the year.
Please provide date of this field verification.
Response: The topographic data was verified with a site visit on December 16, 2021.
David lames
April 14, 2022
Page 4 of 5
4. Sheet C2:
a. Show existing drainage divides.
Response: Drainage Area to sediment trap was previously show. Drainage Area to
silt fence added to sheet C2.0 and C2.1.
b. Please show a paved construction entrance [ACDSM, pg. 81. Contractor can work with
E&SC Inspector should a stone CE be sufficient.
https://www.albemarle.org/home/showpu blisheddocument/270/637202458267970000
Response: Construction entrance updated to the County Standard paved entrance.
Detail on C6.0 updated accordingly.
b. Show sediment trapping device at CE location.
Response: A trapping measure has been added to sheet C2.0.
5. Sheet C6: Label the channels so they can be identified on C3.0.
Response: The chart under the sections identifies the channels and corresponds to the
channel call -outs on C4.0.
6. Show E&SC controls for the pipe & channel. Also, show the grading for the outfall channel.
Response: ESC measures and grading added to the outfall channel.
Please show a phase II E&SC. Notes and E&SC sequence make sense and are helpful guidance
but a second sheet showing these measures in place would provide better clarity.
Response: Sheet C2.1 has been added to show Phase 2 measures.
8. Based on the final grading stormwater will enter the pretreatment area of bioretention and likely
act as a trap. It's unclear how this runoff area will reach the sediment trap.
Response: The bioretention basin will not be constructed until upstream areas are
stabilized. Therefore, the sediment trap will no longer be needed once the forebay is
installed.
9. Have you considered placing the sediment trap at the bioretention location? Consider the cost -
savings. See Section 8.1 Construction Sequencing:
https://swbm pvwrrc.wp.prod.es.cloud.vt.edu/wp-content/uploads/2017/11 /BM PSpec-No-
9_BIORETENTION_v1-9_03012011.pdf
Response: Thanks for the suggestion. We looked into the possibility and this isn't practical
given the grades.
10. Note: Applicable VDOT entrance permit will need to be acquired prior to grading permit
issuance.
Response: Noted; the permits will be obtained by the contractor.
David lames
April 14, 2022
Page 5 of 5
If you have any questions, or would like additional information, please feel free to contact me at 434-
284-4782 of cbolton@daa.com.
Sincerely,
Draper Aden Associates
6 L70�
E. Campbell Bolton, P.E.
Project Manager
Site Development & Infrastructure