HomeMy WebLinkAboutWPO202100056 Correspondence 2021-11-30L I N E + G R A D E
C I V I L E N G I N E E R I N G
COMMENT RESPONSE LETTER
November 30`h, 2021
TO: County of Albemarle
Community Development Department
401 McIntire Road, North Wing
Charlottesville, VA 22902
ATTN: Emily Cox, plan reviewer
RE: Waverly Residence — WPO-2021-00056
Ms. Cox,
On behalf of Cyrena Sparkman we offer the following responses and plan revisions to
comments dated November 3rd, 2021. Our Responses are in bold italic text below each
comment.
A. Storm water Pollution Prevention Plan (SWPPP)
1. SWPPP will need to be updated to include the final approved plans.
The SWPPP has been updated to include the most recent plan sheets.
B. Pollution Prevention Plan (PPP)
1. No Comment.
The PPP has been updated to reflect changes in the underlying phase 2 erosion
and sediment control elements, but no changes to prevention practices have been
made. See plan in the SWPPP.
C. Storm water Management Plan (SWMP)
1. Since this plan is for the establishment of a single family dwelling unit, according to
County Code 17-403-13, an agreement in lieu of a stormwater management plan
can be used. The conditions listed on the agreement must still be met, but your L I N E +
water quality and VRRM requirements (forest & open space easement) may be
removed. The level spreaders must remain to address the concentrated flow.
Please fill it out and submit with your next submission. GRADE
Sheet C5.3 containing the water quality and VRRM requirements, including
C I V I L E N G I N E E R I N G
the conservation easement has been removed from the plan. The stormwater
113 4`" STREET NE, STE. 100
management agreement for single family residence construction is pending
CHAR LILLE, 22902
LINE-G NE-GR
RADE.COM
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Waverly Residence (WPO-2021-00056)
Comment Response Letter
November 30", 20211 Page 2
selection of a contractor (responsible land disturber) and will be submitted
separately once signed.
2. An easement is not required for the level spreaders, however a SWIM facility
maintenance agreement will be necessary before this plan can be approved. Please
contact Ana Kilmer [akilmer@albemarle.org or 434-296-5832 ext 3246) in our
office to complete that process.
We will be reaching out shortly to start this process.
3. Please add the WPO number to the cover sheet, WP0202100056.
The WPO number has been added to the cover and title block. See revised sheet
C0.0.
4. Ensure no proposed slopes are steeper than 2:1. Area before level spreader B
appears to be steeper.
All slopes on the site have been revised to be less than 2:1. See revised sheets
C2.2, C3.0, C4.0, & C5.1.
5. Please show the 25-year storm for the culvert calculations.
The culvert calculations have been updated to include peak flows from the 25-
year return period design storm. Intensity values reflect those found on the NOAA
Atlas 14 website for this location. Culverts remain adequate. See revised
calculations on sheet C5.2. Please note drainage areas have changed to reflect
revised grading.
6. Ensure that all criteria are met for the level spreaders per the spec. Specifically,
please show downstream of the level spreaders (maximum slopes and possible
stabilization measures necessary).
The following revisions have been made to the design of the level spreaders to
conform with DEQ Spec. No. 2, Sec. 6.3 on Engineered Level Spreaders:
• Level spreader length computations have been revised to utilize the 10- I E
year design storm peak flow, since this is an on-line application.
• A 3-foot-wide section of stone underlain by filter fabric has been added to GRADE
each level spreader downstream of the rigid lip.
• Slopes to the depressions behind the level spreaders have been revised to
be 3:1 or less. CIVIL ENGINEERING
113 4`" STREET NE, STE. 100
CHARLOTTESVILLE, VA 22902
LINE-GRADE.COM
Waverly Residence (WPO-2021-00056)
Comment Response Letter
November 30", 20211 Page 3
Calculations have been revised to show the velocity of sheet flow downhill
from the level spreaders as compared with the allowable velocity. Velocities
from the 10-year peak flow do not exceed allowable velocities downhill.
In addition to the above, EC-3 type 1 matting is now proposed downhill of level
spreaders Al and B. A site visit revealed small unvegetated areas downhill of
these level spreaders (see site pictures emailed to reviewer). These problems are
likely due to the recent clearing for agricultural activities and will be rectified
with the proposed erosion control matting and proposed plantings.
Please note a third level spreader has also been added (ELS "A2") to reduce the
total area draining to each level spreader, thereby more closely matching the
predevelopment drainage conditions. See matting on C2.2, revised grading on
C4.0, revised drainage areas on sheet C5.1, and revised level spreader
calculations and detail on sheet C5.2.
D. Erosion and Sediment Control Plans (ESCP)
1. Please add the county erosion control notes to your plans.
The County E&S notes have been added to sheet C2.0.
2. Please provide the paved construction entrance detail with awash rack from page
8 of the design standards manual. Ensure the wash water has a place to drain.
The standard construction entrance detail from the VESCH has been replaced with
the Albemarle County construction entrance detail, see revised sheet C2.3. A note
has been added to provide drainage to the silt fence prior to wash water exiting
the site: a site visit confirmed positive drainage is available. See revised sheets
C2.1-C2.2.
3. Please show dust control on all E&5 sheets.
Dust control is now shown on all E&S sheets. See revised sheets C2.1-C2.2.
4. Please show a construction staging and parking area. L I N E
Construction staging and parking areas are now shown on the plans. See GRADE
revised sheet C2.1-C2.2.
CIVIL ENGINEERING
113 4`" STREET NE, STE. 100
CHARLOTTESVILLE, VA 22902
LINE-GRADE.COM