HomeMy WebLinkAboutWPO201900039 Correspondence 2020-09-0900i 4oltteverde
9/9/2020
Seth Roderick
Monteverde Engineering & Design Studio
250 E Elizabeth St, Suite 114
Harrisonburg, VA 22801
Albemarle County Community Development Department
Attn: John Anderson
401 McIntire Road
North Wing
Charlottesville, VA 22902
RE: Hillcrest Vineyard Tasting & Venue WPO 2019-00039
Mr. Anderson,
The plans that accompany this letter have been revised per the review comments dated September 1,
2020 transmitted by email. The comments have been addressed as follows:
Review comments (plans d. 9/l/20):
1. Confirm if 1.63" orifice dimension at riser is accurate. Where is this?
Response: 1.63 "orifice dimension on detention basin #1 profile view sheet C6.041R revised to 2 ".
2. Provide inset small-scale plan /profile detail that illustrates how riser elements are arranged similar to
6'R basin 1 flow bypass structure, C-6.03R:
a. Check 2" label against 1.63" label —are there two separate elements? If so, provide 1.63"
orifice INV. If not, revise dimensions to match.
Note: Albemarle does not typically approve orifice openings < 3" DIA. Very small orifices
are prone to obstruction /SWM short-circuiting.
Response: Riser structure details shown on sheet C6.043R. To prevent obstruction, a 20'-
min-length perforated leader pipe wrapped in open -graded stone (#57) is incorporated in the
design; as this stone and pipe flood, inflow is controlled by the 2 " orifice, but the 2 " orifice is
never exposed to any debris that cannot enter the stone and perforated pipe. This has been
deemed more effective and less prone to clogging than a debris cage due to length and
combined area. See further description in response to question 2b, below.
b. Unclear how 1070.5' - 2" low flow orifice elevation works with bottom pool elev.=1071.00'
(plan /profile may help resolve).
Response: Base/ outflow, of riser is lower than bottom ofpond. The plan proposes a gravel &
perforated pipe filter in the bottom of the detention basin (elev: 1071.00) that connects to the
riser with solid pvc. The orifice at the end of the connecting pipe will be at Elev: 1070.50.
Hydraulic head will drive the stormwater through the gravel filter, into the perforated pipe,
through the orifice, and out the riser structure.
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RE: Hillcrest Vineyard Tasting & Venue WPO 2019-00039, Albemarle County, Va. Sept 9, 2020
c. If weir plate is proposed interior to riser, show weir plate in plan /profile views.
Response: There is no weir plate inside riser. Low flaw orifice is cut into a threaded pipe
plug (notation provided in riser detail on Sheet C-6.043R).
d. If weir plate is included with design, specify debris cage sized to prevent obstruction of 2"
(or other small diameter) openings.
Response: No weir plate is specified in design. Detention basin #1 uses a gravel and
perforated pipe filter to protect the low flow orifice at the end of the pipe.
e. Ensure small diameter openings are protected against obstruction from items that may pass
openings in riser crest trash rack.
Response: Low flow orifice is cut into pipe cap and is protected from clogging by gravel
filter. Low flow orifice is not subject to impact or clogging from debris passing through the
riser, as it is on the high side of the base.
f. Since height from riser floor to crest =57, show steps in plan view of riser, and ensure no
conflicts with 18" pipe outfall.
Response: After further discussion with John Anderson on Sept 9, 2020, the note
"maintenance access by portable ladder, not permanent steps" has been added in lieu of
steps for Detention Basin #1 riser. This note has been added to Sheet C-6.043R below the
riser detail Note that riser structure for Detention Basin #2 has been modified to an M11-1
with ST-1 steps, due to 7.5' height.
3. Include riser trash rack detail, StormRaxTM for example: https://www.conteches.com/stormwater-
management/treatment/stormrax .
Response: Trash rack detail added sheet C6.043R
4. Include debris cage detail (for small DIA orifices, interior to riser), as needed.
Response: Debris cage detail is not needed. The only small diameter orifice (2" det. basin #1) is
protected by gravellperforated pipe filter assembly. All other orifices are >6 ".
5. C-6.042, C-6.041R: Include Embankment Note 6 requiring PE -certification be submitted to
Albemarle County attesting that `Items specified at Notes L-5. were met by and during construction.'
Response: Note added Sheet C6.041 R, C6.042R
6. Include construction bullet point below from p. 17 of VA DEQ Stormwater Design Specification No.
2 on C-6.041R (basin # 1).
• Construction of the gravel diaphragm or engineered level spreader shall not commence until
the contributing drainage area has been stabilized and perimeter E&S controls have been
removed and cleaned out.
Response: Note added sheet C6.041R.
7. Add note at ELS detail, C-6.041R blue circle, image below rt., requiring each end of 56' ELS be
embedded 2' in surrounding fill.
Add note to construct a rising 4:1 slope (2:1, max.), away from each end of embedded ELS to ensure
concentrated flow does not cut a path around either end of the ELS.
Additional detail re. this item: please see email sent August 28, 2020 1:25 PM.
Response: Note added sheet C6.041 R indicating 2' lip burial and compacted slope on either end of
ELS.
8. Recommend label basin #2, C-6.03R. (unless it is labeled, and overlooked)
Response: Label added to detention basin #2 on sheet C6.03R.
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RE: Hillcrest Vineyard Tasting & Venue WPO 2019-00039, Albemarle County, Va. Sept 9, 2020
9. Provide note and detail for anchors for 18' — 15" CMP @ 33% ; ref. VDOT Drainage Manual, 9-37.
18" CMP WITH F.E.S. 60 FT ® 1.0%
INV IN : 1070.40'
INV OUT: 1069.80'
CONCRETE FLOW BYPASS STRUCTURE
6' DIA. 4' HEIGHT
RIM: 1072.10 RIF
WEIR CREST: 1070.10 TO
OF
;RETE
ON BASE
AT RISER FOR
& CLEANING
�CALQ
VDOT Drainage Manual, 9.4.8.7:
N V1hk..ifirt7J 90
INV OUT: 1063.00
GE-
FAI
CO
BO
SIC
9.4.8.7 Maximum Grades
Slopes that incur uniform flow velocities in excess of 10 fps should be avoided because
of the potential for abrasion. Slopes in excess of 16% are not preferred because of the
need for anchor blocks. When anchor blocks are used, they should be installed at
every other pipe joint, as a minimum. (See Special Design Drawing No. A-73 and MA-
73 for Anchor Details for Concrete Pipe)
Corrugated pipe may be used on steep slopes in situations similar to those where
shoulder slot inlets are proposed. Corrugated pipe should not be used in areas where
the flow is expected to carry an abrasive bed load or that have PH and resistivity factors
beyond the ranges specified in the Allowable Pipe Type Table C in Standard PC-1 of
the VDOT Road and Bridge Standards. (See VD0J& Road and Bp pl-1,
for Anchor Details for Corrugated Pipe)
Response: Note added in plan/profile (sheet C6.041R) 15"pipe @ 33% to be anchored per detail PI -
I (sheet C6.043R).
10. Include VDOT 2016 R&B Anchor detail for CMP, PI-1
Response: Pipe anchor detail added sheet C6.043R.
11. As follow-up to Item 2.e., email (August 21, 2020 6:05 PM); option a /b:
a. Item 2.e. states: `Revise /amend WPO201900039 recently -amended ESC Plan to reflect
measures required to construct detention basin'. Item 2.e. with this email is revised to read
/require: `Provide note on SWM Plan Amendment to `Reference ESC Plan Amendment #2
for ESC plan measures relating to basin #2 construction." At this point, we leave it with
Monteverde, but envision a straightforward single sheet Amendment #2 (WP0201900039
ESC Plan) that provides measures needed to construct basin #2, in phases (access/clear,
construct, stabilize basin #2). A single sheet divided into quadrants might suffice; for
example —quad/phase 1: access /clearing /perimeter measures; quad/phase 2: basin #2
construction; quad/phase 3: final stabilization; 4t' quadrant, details /notes.
OR
b. Revise C-0.01 Note, last sentence, since next SWM plan sheet does present ESC
measures. Reference ESC measures in revised C-0.01 Note. C-3.02-B:
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RE: Hillcrest Vineyard Tasting & Venue WPO 2019-00039, Albemarle County, Va. Sept 9, 2020
i. Include additional measures and/or sequencing notes that consider all aspects of
basin #2 construction.
ii. Provide corresponding measures, clearing thru final stabilization.
iii. Label basin #2 construction access.
iv. Provide construction entrance (CE) detail.
v. Provide TS, PS, MU.
vi. Note: With this option, Albemarle does not request Amendment to ESC Plan
(Amendment #1), but would instead rely on SWMP, and be guided by C-3.02B.
Response: Detention basin #2 construction erosion and sediment control measures for phase 1, 2,
and 3 shown on C3.02B.
12. As follow-up to email (August 28, 2020 10:45 AM, J. Anderson to Lisa Perry, Monteverde), and as
follow-up to conversation between Seth Roderick and County Engineer, please delete sentence, Calc.
packet, p. i., that reads: `The slope below the level spreader will be mitigated with earthen berms for
65'.'
This statement appears unnecessary given conversation with Albemarle County Engineer, and
assurance that vineyards are planted below basin #L Please delete stated reference to earthen berms,
since request for downslope earthen berms is withdrawn at this time.
(Also: email, F. Pohl to J. Anderson, September 2, 2020 9:38 AM. Also, Monteverde comment
response letter, 9/l/20, p. 5, referencing discussion with Albemarle County Engineer on 9/1.)
Note: Photos taken by inspector (attached to email 8/28/2020 10:09 AM) do not (appear to) indicate
vineyards below basin #L
For this reason, vineyard planting assumed to have occurred between time photos taken and
discussion with county engineer Sep-L
Response: Statement in calc package referencing earthen berms deleted. Vines proposed to be
planted down slope of the ELS are not part of this project and cannot be relied upon. Areas indicating
vines on sheet C6.02R are the areas currently planted. Proposed vine locations have been removed
from the plans. The current land cover for the slope below the proposed ELS is brush and dense
vegetation as of 812812020 (John Yerby Photos).
13. C-6.03R: Label basin #2 SWM facility access.
Response: Detention basin #2 access label on C6.042R has been added to C6.03R as well.
14. C-6.03R: Add note that `Existing permanent fill diversion is installed and was observed to be
adequate during site visit on 6/27/2020 by Monteverde design professional.'
Response: Note added sheet C6.03R.
15. C-6.041R: If vineyards are planted below proposed ELS / basin #1 /Ex. SB, restore graphic image of
vineyards (Typ.) below basin #1 (visible /shown with C-6.041R on 8/7/20 plan), to indicate vineyards
exist.
Image, below, 8/7/20 vineyards circled.
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RE: Hillcrest Vineyard Tasting & Venue WPO 2019-00039, Albemarle County, Va. Sept 9, 2020
ERFORATED PVC WRAPPED IN #571
& NON -WOVEN GEOTEXTILE, CAP
INAL END, MOUND ASSEMBLY WITH)
#57 STTOONEE` 16" HIGH, 2' WADE
_OW ORIFICE PLATE TO BE INSIDE
ACCESSIBLE FOR MAINTENANCE
AND CLEANING
SEE DETAIL C6.041-R - /
/ UPPE
/ UPPER
Response: As of last site visit vines were not installed as shown in above referenced sketch. Vines
proposed to be planted down slope of the ELS are not part of this project and cannot be relied upon.
Areas indicating vines on sheet C6.02R are the areas currently planted. Proposed vine locations have
been removed from the plans. The land cover for the slope below the proposed ELS is brush and
dense vegetation as of 812812020.
16. Pg. 4 comment response letter indicates POA shift, per county request. Please all sheets carefully;
edit /delete or relocate labels, as needed. For example:
a. C-6.02R: Label that reads New Road 0.16 Ac. to drain as sheet flow to PDA A. [ Delete ref.
to PDA A.]
b. C-6.02R: Post development drainage to POA A 48.15 Ac.
c. C-6.01R: PDA A label near Agricultural pond
Response:
a. Label revised, reference to POA A removed.
b. Label revised to read "Post Development Drainage area 48.15 Ac"
c. POA label and indication point removed.
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RE: Hillcrest Vineyard Tasting & Venue WPO 2019-00039, Albemarle County, Va. Sept 9, 2020
17. C-6.03R; basin 1 flow bypass structure: Provide grate or similar at 15" pipe outlet across entire 15"
DIA, since 6" riprap in 6' M 4 ring extends below 15" pipe INV, slightly. Design must prevent riprap
dislodging /obstructing 15" pipe to ELS.
Resoonse: Detail has been modified to specify grouted riprap, with note added to indicate riprap not
to be placed higher than invert of 15 " outlet pipe at outf d/. Depth of riprap revised to be 0.75'.
According to the stormwater calculations a 10yr storm event (4.3 cfs) exiting detention basin #1 will
not be erosive to 6" riprap outlet protection; grout will ensure riprap does not dislodge. Additional
notation added that standard MH-1 base may be utilized in lieu of grouted riprap.
It is my hope that these revisions accurately and adequately address your comments. Should you have
any follow-up questions upon review of this re -submittal, please contact me at your earliest
convenience.
Thank you,
Seth Roderick
Managing Partner
Monteverde Engineering and Design Studio
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