HomeMy WebLinkAboutWPO201900053 Review Comments WPO VSMP 2020-04-06COUNTY 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
Project title:
Eco Village Charlottesville
Project file number:
WP02019-00053
Plan preparer:
Shimp Engineering Justin M. Shimp; Keane Rucker
Owner or rep.:
Ecovillage Holdings Inc.
Plan received date:
23 September 2019
(Rev. 1)
25 Oct 2019
(Rev. 2)
28 Feb 2020
Date of comments:
10 October 2019
(Rev. 1)
4 Dec 2019; rev. 13 Dec 2019 (response to 12/12 Meeting)
(Rev. 2)
6 Apr 2020
Reviewer:
WW Associates (J. Anderson, Rev. 1, 2)
Cc:
Tim Padalino, CDD /Planning
If text is grayscale, comments addressed. New orfollow-u comments are included, and listed, below. Additional
follow-up comments a possibility.
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 project is subject to
qpproved SP201800056.
This SWPPP is disapproved, and the reasons are provided in the comments below. Note: It appears SWPPP
d. 2/21/20 addresses few if any comments —it appears the initial version may have been submitted.
1. Notice of general permit coverage (Rev. 1) Pending. Applicant (10/24/19): `Notice of general permit
coverage cannot be included until the land disturbance permit is issued. We add this document to the
SWPPP at the preconstruction meeting.' (Rev. 2) Comment persists. Applicant response (2/21/20):
`Pending —no action until precon meeting.'
2. Nature of the activity (use/development of the site, not the E&S controls). It should refer to redevelopment
of the site, number of units, parking, private roads, support structures and stormwater controls. The
narrative provided properly belongs in Section 4. (Rev. 1) Partially addressed. As follow-up: Minor edit —
Please revise description to reference 38 units. (Rev. 2) Not addressed.
3. Qualifications and contact information for qualified personnel (Rev. 1) Addressed. Applicant: `Qualified
personnel have not been selected yet, this will happen after the project is bid. A note stating this has been
added.'
4. Signed certification
5. Delegation of authority (Rev. 1) Withdrawn. NA at this time
6. The cover and site plan sheets state that 36 units will be constructed, although it appears that 38 units will
be constructed. Please revise wherever it appears.
7. Please include the WPO number above on the cover sheets of the plan, SWPPP and calculations.
8. Please note that additional comments may be generated based on the response to the comments provided.
New
9. Sec. 1, Registration Statement, p.2, Sec. III (A.,13.), Offsite Support Activity Location Information: Revise.
Engineering Review Comments
Page 2 of 11
If data unknown, please enter: Project requires offsite support; location information TBD (or similar).
(Rev. 2) Not addressed.
10. Sec. 1, Registration Statement, p.2, Sec. IV, E —MS4: Enter: Albemarle County, since project within MS4.
(Rev. 2) Not addressed.
11. Sec. 1, Registration Statement, p.3, Sec. IV, F: Check }_es, since project is a common plan of development.
(Rev. 2) Not addressed.
B. Stormwater Management Plan (SWMP)
VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This
plan is disapproved.
1. Show permanent drainage easement recording information on all parcels crossed by the Al-A-4 stormwater
conveyance piping and structures. 17-304.E. (Rev. 1) Persists. Applicant: `Noted, this is still being
obtained.'
2. Provide Albemarle County General Construction Notes for Stormwater Management Plans (three notes).
3. Provide buoyancy calculations for the sedimentation basin riser and the anti -floatation details.
4. Revise the principal spillway detail to show the base (see the previous question).
5. Provide calculations that demonstrate compliance with SP201800016, including hydrographs, routing
calculations and other necessary documentation that the proposed stormwater system is adequate to manage
the 25-year storm without downstream flooding. (Rev. 1) Partially addressed. Asfollow-up: See item
28.1., below. (Ref. pg. 97 of .PDF document of 10/25/19 SWM Calculation Packet — Link 12L.) (Rev. 2)
Comment persists. Applicant response: `(Same response will be used for 281., below) Noted, however the
velocity data is shown on the LD-204, not in HydroCAD Link 12L. We use a different software to
determine velocity. The pipes have velocities <10 fps, except for section A3-A2. We have made this
section of pipe less steep. However, for the flow through this pipe, we would have to reduce the slope to
11 % to achieve a 2-yr velocity of <20fps. This represents a rather significant change in the design.
9VAC25-870-66.B.1.a. specifies that peak flow through manmade systems not cause erosion. We do not
believe that abrasion is of concern for this system, due to the onside nutrient and sediment treatment
provided. Furthermore, we have specified a more durable pipe material (ADS HP -Storm is polypropylene).
This material is designed for high performance applications, including abrasion resistance. See attached
report. Thus, we request that county engineering approve this layout.' Statement at VAC25-870-66.B.1.a.
is a regulation; technical resources (specifically VDOT Drainage Manual) set quantitative limits (standards)
to guide implementation of the regulation at 9VAC25-870-66.B. La.. Albemarle County Design Standards
Manual is another; Alb. Co. Drainage Plan Checklist is another. It is important to ref. 9VAC, but critical
to rely on technical resources that are basis of plan review /approval (VDOT, ACDSM, review checklist).
Engineering relies on multiple publicly -available resources (item 13, below /image); revise design to ensure
V2_yr A3-A2 more nearly aligns with VDOT Drainage Manual 10 fps design standard. Initial design that
reflects published VDOT, ACDSM, county checklists may help limit subsequent plan revision effort in the
future. Approving flow velocity twice the standard may reasonably be assumed to invite twice the abrasive
conditions anticipated by VDOT Drainage Manual standard. There does not appear to be a compelling
reason to abandon VDOT Drainage Manual 9.4.8.7 10 fps standard for storm line A3-A2.
New (Rev. 1)
6. C4, General: Provide, show, label VDOT GR-2 (guardrail) on south side of lower parking, consistent with
pending FSP comments, and recent Oak Hill Convenience Store review comments /discussion (unrelated
project). (Rev. 2) Comment persists. 2/21/20 Applicant response: `Noted, this is still being obtained.'
(Rev. 2) Addressed. Note /C4, New Segmental block walls. 5' Max height each, Avg. 4'. GR-2 Guardrail
for top wall.
7. C5: Building Lot/Str. 7A is partially within drainage easement. Revise structure /easement location. (Rev.
2) Addressed.
8. C5: BMP D label (blue eir-oled to*t image, below; image deleted with Rev 2 comments) is ambiguous.
Please revise for clarity. (Rev. 2) Addressed.
9. C7, Stormwater Note 6. mentions BMP C, Cl, C2 —there are just two biofilters; please revise for clarity.
(Rev. 2) Addressed.
Engineering Review Comments
Page 3 of 11
10. C7, Stormwater Note `D'. Please renumber this, as Note 7. (Rev. 2) Addressed.
11. C7, Offsite Areas: Identify offsite areas as pre -requisite to Grading Permit. (Rev. 2) Addressed.
12. C8/C9: Label existing culverts under Rio Road E (X4, X3, X2, X1). Use light grayscale to indicate
existing. (Rev. 2) Addressed.
13. C13: Provide VDOT Anchoring detail. See VDOT Drainage Manual, 9.4.8.7 —image, below. Note caution
against corrugated pipe (if excessive abrasive bed load); slopes in excess of 16%; and flow velocities in
excess of !kf
ps. Revise design as needed. (Note: Storm profile Al-A5 is excessively steep). (Rev. 2) Not
addressed. Applicant response: `Noted. Anchoring detail added to C12. We are not concerned about
abrasive bed loads as full onsite treatment is provided, thus runoff flowing through the steep portion of the
pipes will be clean. As such, we consider high -velocity flow through these sections of pipes to be
acceptable as low abrasive loads should not significantly contribute to pipe wear.' Al-A5 conveys runoff
for the entire development, including undetained, untreated surface runoff which may carry abrasive load.
Anchoring detail not located on C12 or C13 —please direct reviewer attention to VDOT anchoring detail.
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 VDOT's Road and Bridge Standard PI-1,
for Anchor Details for Corrugated Pipe)
In steeper terrain, large elevation differences can be accommodated using drop
structures, otherwise known as "step down" manholes, to reduce the pipe gradient.
Rev. 7/14
Chapter 9-37 of 70
14. C13: Add SL-1 labels to Str. A4 and Bin profile views. Note alone is more likely to be overlooked.
(Rev. 2) Addressed.
15. C13: Str. A5A INV OUT is shown as 387.50 and 386.50 in separate profiles. Please reconcile. (Rev. 2)
Addressed.
16. C13: Str. C1 — INV IN < INV OUT. Check /revise. (Rev. 2) Addressed.
17. C13: G1 - G2 profile — Eliminate 12" X 8" reducer, since Min. storm pipe DIA —12". (Rev. 12/13)
Withdrawn.
18. C13: B2 - F1 profile — Eliminate 12" X 8" reducer, since Min. storm pipe DIA —12". (Rev. 12/13)
Withdrawn.
19. C13: B2 - E3 profile — Provide MH at proposed 22-deg bend, and any location flow is proposed to change
direction other than within a MH (I1 - I3, for example). (Rev. 12/13) Withdrawn, per 12/12 discussion.
Also, item 26.h., below.
20. C13: Provide a E2 - E1 profile — Ref. Calc. report, pg. 57. (LD-229 Table) (Rev. 2) Addressed.
21. C13: Revise E2 - E1 slope to 16% Max., else provide VDOT anchors. (Rev. 2) Addressed.
22. C13: Revise 6" PVC storm pipe design per Min. pipe DIA comments, elsewhere. (Profile I2 - IA2) (Rev.
12/13) Withdrawn. Also, item 26.h., below.
23. C14: Provide biofilter floor dimensions. Label biofilter contours in detail plan views. (Rev. 2) Addressed.
24. C15: Add flow lines to detail 1 internal to Isolator Row, StormTech chambers, Bayfilter, weir, bypass, etc.
Additional follow-up comments relating to this are possible. (Rev. 2) Addressed.
Engineering Review Comments
Page 4 of 11
25. C15: Consider /revise ADS Sheet 4 red text; examples: "The outlet invert needs to be lowered...," "The
Design Engineer must check..." (Rev. 2) Addressed.
26. Provide standalone SWM Plan (1+ sheets). At present, there are only SWM details, no dedicated plan, or
comprehensive SWM plan (view). SWM Plan should include:
a. Drainage divides. While Calculation packet includes drainage divides, plan review requires
graphic drainage information on the plan. Copy /transfer p. 7 (of .PDF) of SWM Calc. Packet to
VSMP /WPO Plan. (Rev. 12/13) Withdrawn.
b. Show and label 1.26 Ac. Forest /Open Space Easement. (Rev. 2) Addressed. Revised to either
1.06 or 1.07 Ac. As follow-up: See item c., below. Revise for consistency.
c. Confirm Forest /Open Space Easement lies on hydrologic soil group type `A' soil. Also, ensure
1.26 Ac. Forest /Open Space Easement meets DEQ land cover guidance, April 2016, table, pgl2
/.PDF. (Rev. 2) Partially addressed. As follow-up: Ensure C11, Note 9 (1.06 Ac. Forest /Open
Space) and VaRRM.xls post -developed site table (1.07 Ac.) are consistent (Calc. booklet, p. 8).
Link: hM2s://www.deg.vir ig nia.gov/Portals/O/DEQ/Water/StortnwaterManagementNRRM/GM14-
2001%2OVirginia%2ORunofi/o2OReduction%2OMethod V3.pdf
d. Provide and label public drainage easements for all storm pipes downstream of SWM Facilities,
including individual raingardens, to the development property line. Ref. 14-431.A.1. (Rev. 2)
Partially addressed. As follow-up: C-11, revise labels for A-, B-series of rain gardens to indicate
typical easement. For example, 13-15 label to read New Public SWM Facility Esmt (Typ, I of 15).
Each rain garden requires public SWM Facility Esmt.
e. Show and label BMP D. (Rev. 2) Addressed.
f. Show and label (1. - 38.) raingardens that will be built with individual lots, that will be bonded
with this WPO, and that are necessary (collectively and individually) for SWM quality
compliance. (Rev. 2) Addressed.
g. Provide plan sheet Note to identify raingarden area (SF) for facilities installed at Lots 18A-23A.
(Rev. 2) Partially Addressed. Asfollow-up:
i. Provide Note similar to text, below (ii), for facilities installed at Lots 18A-23A.
ii. Copy note below from sheet C6 to CI L
NOTE:
ALL RAINGARDENS ARE LEVEL 1 BMPS.
LOTS 113-153 SHALL HAVE RAIN
GARDENS WITH A 67 SF FOOTPRINT.
h 6" or- 4" DIA storm pipe is disaUowe Revise design. Revise LD-229 tables. (Rev. 12/13) As
follow-up: On this site given site constraints and design objectives, Min. 8" DIA HDPE is allowed
(Typically, with rare exception [other than Nyoplast® yard grate systems], a Min. 12" DIA is
required for storm lines in easement/s. See Drainage Plan checklist). 8" X 12" reducers will be
allowed since we anticipate no debris in HDPE raingarden collector lines. Most bends without
MH Str. are allowed, in this instance. Proposed T-connection should be reviewed, carefully. T-
connections are rarely (if ever) seen in gravity storm systems other than at a MH Str. Engineering
will evaluate revised T-connection, and encourages alternative design. Last: provide cleanouts at
terminal ends of raingarden collector lines, and intervals spaced not more than 150' apart. (Rev. 2)
Partially addressed. Applicant response: `Noted. Following Engineering's request, we added
adequate number of cleanouts at terminal ends and —100' intervals. All bends more than 25' from
another cleanout/drain basin now have cleanouts. Str. G1 T-connection revised to be a 24" drain
basin.' As follow-up: Label cleanouts in plan view (C11). Revise IS-1 Note, C14, or wherever it
occurs, since inlet shaping is required for structures irrespective of whether drop is 4' or greater.
i. Show and label two (2) Level 2 bioretention basins. (Rev. 12/13) As follow-up: Also, see item
26.k., below, for comparable level of VA DEQ Stormwater Design Specification No. 9
bioretention installation, inspection, and maintenance detail to include with VSMP /WPO plan.
(Rev. 2) Partially addressed. As follow-up: Provide refence on CI I to installation, inspection and
maintenance details on sheets Cl and C7.
j. Since retaining walls are proposed to the south side of the lower parking lot, shift Bayfilter
Engineering Review Comments
Page 5 of 11
Treatment System and ADS StormTech systems (incl Isolator Row) north and slightly west, to
avoid conflict with segmental block retaining wall anchoring geogrid, and to help preserve parking
during (eventual) future system replacement /maintenance, to maximum extent practical. (Rev.
12/13) As follow-up: Engineering continues to hold it is the long-term interest of development
residents if the stormwater management system shifts, as outlined, north and slightly west. Also,
County Engineer requests plan /profile detail of splitter /weir. Provide a manwav or observation
ports for both chambers of the StormTech system, if possible. At a minimum, provide manwav
access to flow splitter /weir structure, and ensure access is located outside of parking spaces. (Rev.
2) Partially addressed. Applicant response: `Stormwater system cannot be easily shifted due to
the multiple alignments of pipes entering the system. Also, since this is a 1-way, single aisle,
angled parking lot, replacement of the system would obstruct the drive aisle regardless of BMP
location. (Hopefully, by the time the system is replaced, that parking area will be greenspace
instead of vehicle storage which would be in alignment with the future goals of the development.)
Plan/profile detail of splitter has now been provided. Profile of system now provided. Manway
access to the flow/splitter structure has been provided, outside of parking spaces.' While structure
B 1 is not in a parking space, 36" solid lid /steps to Bayfilter is. Relocate manway access to the
Bayfilter outside any parking space. Please address with next submittal (blue circle, image below).
i. Also, as follow-up: Provide ref. to Structure B splitter detail located on C17 on C11
(permanent SWM plan) and C14 (storm profiles).
ii. Revise C17 Structure B Splitter Detail caption to ref. Structure B1.
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k. CT Provide installation, inspection, and periodic maintenance Notes for raingardens; inspection
and periodic maintenance Notes for bioretention basins similar to Notes provided for Bayfilter
BMP. Ref. VA DEQ Stormwater Design Specification No. 9 (and Attached). (Rev. 12/13) As
follow-up: Please ensure Spec. 9, Sections 8.2, 8.3, 9.2 thru 9.4 for raingardens, transfer to plans,
and inform design. Note design specifications for raingardens, Table 9.2. Plans should identify
Level 1 or Level 2 design. Captions for details on C5, C6 should identify whether typ. detail is
Level 1 or Level 2. Include specification for media mix test. Above are specific Albemarle
County Engineer requests. Thirty-eight raingardens to be built with residences, likely by builders
not developer, on separately -owned private lots require initial care in design and installation, while
inspection and maintenance will be essential. Easements must provide private or public access to
Engineering Review Comments
Page 6 of 11
inspect, repair, maintain or replace raingardens. (Rev. 2) Addressed. Ref. C19. Note: ensure text
is readable at print scale.
27. Revise all 6" — 8" HDPE or PVC storm pipe to 12" DIA Min. See drainage Plan checklist for plan
reviewers, pg. 2, Drainage computations, pipe computations, which reads: `For systems within drainage
easements, all proposed pipes are a minimum 15" in diameter.' (Rev. 12/13) Withdrawn. See item 26.h.,
above.
28. SWM Calculation Packet
a. Pg. 7: DA `A' and DA `B' raingarden CF is slightly inconsistent with C5 - C6 raingarden details.
Revise for consistency. Check SF v. CF descriptions. (Rev. 12/13) Partially addressed. As
follow-up: Please check DA D and DA E (purple text) labels. These labels appear to identify DA
E, only. (Rev. 2) Partially addressed. As follow-up: Copy SWM Notes (1.-9.) from C7 to C11.
These notes must be on this sheet. Confusion may result from absence (not presence) of notes.
b. Pg. 21: Compare 6" PVC Inv. =441.5' with C14 /Biofilter C1 6" PVC Inv. =441'. Revise. (Rev.
2) Addressed.
c. Pg. 21: Revise Pipe Out Inv. Elev. (table value), consistent with C14. (Rev. 2) Addressed.
d. Pg. 21: Compare 15" HDPE OUT vs. 12" HDPE OUT with C14 /Biofilter C2. Revise. (Rev. 2)
Addressed.
e. Pg. 21: Check /revise table DA C-2 Pre-treatment Vol. (Rev. 2) Addressed.
f. Pg. 21: Biofilter bottom area (sf), 660 and 155, inconsistent with C14 profiles. Revise. (Rev. 2)
Addressed.
g. Pg. 22 thru 50: Relocate select material to plans. SWM Cale. Packet will not guide construction
installation, inspection, or periodic maintenance (an obscure location for this data). Transfer
relevant data to plans. (Rev. 12/13) As follow-up: Not all 28-pg of material needs to transfer to
the plans. Consider range of material already included on C 15, refer to very useful descriptions on
C7 for Bayfilter BMP (Installation, Inspection, Maintenance), and please ensure comparable data
is included for the ADS StormTech detention system. It is possible minimal additional BMP
installation, inspection or maintenance material now included in the Cale. packet should transfer.
(Rev. 2) Addressed.
h. Pg. 53-54: Transfer to plans. (Rev. 12/13) Withdrawn.
i. Pg. 55: Revise C2 and D2 throat length: C2, so no carryover across lower parking lot; D2 since
any carryover at this inlet is untreated, yet inlet is included in `treated' DA. (Rev. 2) Partially
addressed. As follow-up: Revise catchment area for Str. D2 since less than initial 0.34 Ac., and
check design calculations. Ensure all LD-204, LD-229 values are accurate. QC all values.
j. Pg. 55: Revise A5Z throat length so no carryover; project may not release carryover into Rio
Road. (Rev. 2) Partially addressed. Asefollow-up: A5Z (now A6Z) listed in LD-204 (p. 76 /Calc.
booklet) with identical catchment area and runoff coefficient. Post-dev inlet drainage maps appear
identical between this /last submittal. Clarify how 0.03 cfs bypass (last submittal) is reduced to
0.0 cfs, with this submittal if design parameters are constant. Also, item i., above. QC all values.
k. Pg. 57: Revise LD-229 table, as needed, to reflect revised Min. storm pipe DIA. (Rev. 2) Partially
addressed. As follow-up: Design flow in pipe A5-A4 appears to exceed pipe capacity. Revise
/QC all values.
1. Pg. 97: Provide Additional Link 12L data (velocity for comparison with channel protection
requirements at 9VAC25-870-66.B.1.a. 2-yr. vel. (in pipe) Max. =20 fps. Also, size riprap at
outfall near Meadow Creek. If riprap design is overlooked, please notify reviewer. (Rev. 2)
Partially addressed. As follow-up: See item 13, above (revise /reduce max. velocity). Also, item
49, below.
New (12/13/19 rev.)
29. Storm lines need not be centered within drainage easements. (Rev. 2) Addressed.
30. Min. easement width for raingarden collector lines =10'. (Rev. 2) Addressed.
31. Locate easements such that there is 2'-3' minimum clearance to any portion of a structure (footing, deck
support, etc.) In the future, current design participants /developer may be unavailable to mediate disputes
Engineering Review Comments
Page 7 of 11
concerning right of access to repair or replace structures located within public drainage easements. (Rev. 2)
Addressed. Applicant response: `Noted, 2' clearance from storm pipes, and rain gardens, to all home
structures has been provided. Easements as shown next to the homes are due to tight configuration. Please
note that we have been working with the architect for this project, home layout is not conceptual, but
represents each lot's building. Thus we are confident in the tight spacing shown herein, as the developer
will not offer other house footprints.'
32. With revised design or storm line placement, please ensure minimum water line v. storm line horizontal
/vertical offset. Similarly, ensure minimum sanitary line v. storm line horizontal /vertical offset -clearance.
(Rev. 2) Addressed.
33. Curb for private street is required. (Rev. 2) Partially addressed. As follow-up: Wherever proposed grade
concentrates storm runoff against curb, revise CG-2 to CG-6 to provide gutter as required at 18-4.12.15.g.
34. Revisit super -elevation in 70' R curve. (Rev. 2) Comment persists across site /road plans. Addressed on
VSMP /WPO plan. Applicant response: `Super -elevation provided. Details will be shown on road plans.'
35. Ensure no drainage release to Rio Road E. (Rev. 2) Addressed.
36. Curb cuts are an option; release of uncontained runoff across lower parking lot is not an option. (Rev. 2)
Addressed. Applicant response: `Noted, this is no longer an issue.'
37. All easements downstream of raingardens are public drainage easements. (Rev. 2) Addressed.
38. Consider effectiveness of pretreatment vis-a-vis proposed grade for private street, Road A (blue circle area;
image, blow). (Rev. 2) Comment withdrawn. Applicant response: `We believe this will be an effective
pretreatment, the 2% cross slope is unlikely to cause erosion at the edge of pavement/sidewalk from
sheetflow. Native grasses will function as a pretreatment for debris, and gentle slopes to the grass, and then
right before the biofilter C, will protect against channelization and/or erosion.'
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39. Recommend continuous SWM Facility Easement fronting units 9A thru 16A, to provide easement access to
raingardens sandwiched between drives. Image, below (blue -circled area, left). (Rev. 2) Partially
addressed. Revise line types to show 10' public drainage easements (to include portions of raingardens).
Then, for portions of raingardens lying outside public drainage easements, define new public SWM facility
easement line type, and carry these through to the easement plat. Provide Note on plans that SWM
facilities collectively will be maintained by the HOA. If this is not the case, if individual raingardens are to
be individual owners' responsibility, please revise locations of raingardens so that SWM facility easements
do not cross any lot lines (so facility maintenance and county access to any given rain garden involves a
Engineering Review Comments
Page 8 of 11
single property (lot) owner). Both easement types are dedicated to Albemarle, to public use.
40. Propose `delineators' for geogrid /grass-pav e fire -rescue access (Roads B, C, D) to limit vehicles operating
beyond stabilized geogrid. Image, above (blue -circled area, right /Typ.). (Rev. 2) Addressed. Applicant
response: `Noted, luminaire bollards have been provided at 20' intervals.' Asfollow-up: Label luminaire
bollards, C3.
41. Albemarle recommends propose raingarden collector lines at (minimal) depth that still meets material
design specifications for minimum cover, and minimum slope. (Rev. 2) Addressed.
42. Ensure all individual lot lines are shown, that lot lines continue to exterior property boundary, and provide
a complete boundary for each lot —this is not a request for platting, but to help ensure raingardens do not
cross lot lines. (Lots 213, 313, 413, for example.) (Rev. 2) Addressed. As follow-up: While raingardens do
not appear to cross lot lines, twenty-three (or 24) of thirty-eight (SWM facility) easements for individual
raingardens do, which may be problematic. Ref. item 39, above.
43. Raingarden for Lot 7A appears to be located on Lot 8A. This cannot be approved. SWM Facility for Lot
7A may be located in common, or open HOA space, but not another private residential lot. (Rev. 2)
Addressed.
44. Raingarden collector line for Lots IA, 2A (storm J2 J1) appears to dead-end. Ensure these raingardens
on these lots connect with downstream treatment. (Rev. 2) Addressed. Applicant response: `The collector
line for these rain gardens runs under a flume in the sidewalk and outlets into the pavement. This area does
not run into BMP E, however BMP E would provide minimal extra treatment for 3000sf. We have
designed a 0.14 lb. treatment buffer into this development. For these 2 lots, there is a phosphorous load of
0.12 lbs. Treatment via rain gardens removes 0.07 lbs. The remaining 0.05 lb. of load would be routed to
BMP E, which would provide a 70% removal (0.7* 0.05 =0.035 removed, if routed to E). Thus, not routing
these lots to BMP E, means that 0.035 lb. are not treated. This is covered by the treatment buffer already
built in.' As follow-up:
a. C11: Clarify whether rain garden collector line is 8" steel beneath sidewalk (trench drain),
b. If flume is a surface feature in sidewalk, provide detail consistent with VDOT standard sidewalk
detail (reviewer cannot visualize flume as a surface depression in sidewalk),
c. If flume is raingarden collector line that transitions to a trench drain at this location, provide detail.
Engineering Review Comments
Page 9 of 11
d. (If d., then...) C11: Revise steel sidewalkflume label to include ref. to trench drain detail.
e. If J1, J2 raingardens outfall to paved surface, extend new 10' public drainage easement from CG-2
at parking area west of Unit IA, across parking area to Str. A6C, to Str. A613, then Str. A6A, then
to Str. A6. Note: wherever grade concentrates flow against CG-2 west of Unit 1A, revise to CG-6.
(Also, item 33, above.)
f. Add labels /notes that clarify design intent at outfall, storm profile J142, C14.
45. Include Construction Record Drawing (As -built) for VSMP (.PDF) on the plans; link:
http://www.albemarle.org/upload/images/forms center/departments/Community Development/forms/En ing eerie
g_and WPO_Forms/WPO_VSMP_Construction _ Record_ Drawings Policy 23May2014.pdf (Rev. 2)
Addressed.
New (Rev. 2)
46. Provide match line, C5-C6.
47. Calc. booklet: rotate p. 43 180-deg.
48. Rotate C2 90-deg counterclockwise.
49. Copy OP (riprap) L X W X D data (Str. Al at Meadow Creek) from table on C13 to plan view at C15.
50. C15: Revise sheet title to Biofilter & Offsite Storm Sewer Details.
51. C4: Provide grading plan for storm sewer between Rio and Meadow Creek, if change in grade proposed
(C15 shows no proposed grading). If no change in grade proposed, provide note on C4 to that effect.
52. C4, C8: Provide labels on these sheets to C15 for offsite storm sewer details, as is provided on C5.
53. C15: Provide measure to dissipate CWD channelized flow at base of slope prior to discharge to Meadow
Creek. Ref. VESCH Plate 3.15-1, since the CWD channelizes flow like a TSD.
C. Erosion and Sediment Control Plan (ESOP)
Virginia Code §62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESOP. This plan
is disapproved for reasons listed below. The erosion control plan content requirements can be found in
County Code section 17-402.
1. Sheet C2 has overlapping labels, making them difficult to read. Please revise.
2. Sheet C2 does not show all of the disturbed area (omits the sanitary sewer and stormwater piping offsite).
Please revise. (Rev. 1) Addressed. Asfollow-up: Please show full extent of storm pipe conveyance
between Rio Road E and Meadow Creek, ESC, Phase 2, C9 (see C2 /Matchline, which shows pipe to
creek). Show Phase 2 ESC measures required to install this stormwater pipe. (Rev. 2) Partially
addressed. Applicant response: `offsite disturbed area now shown on C2.' Asefollow-up: C2 displays
existing conditions and demolition. Address items 49-53, above.
3. Sheet C7 Offsite Areas narrative appears to have a typo. Please clarify. (Rev. 1) Addressed. As follow-up:
Please revise offsite narrative, if offsite locations identified. At a minimum, by preconstruction meeting
and prerequisite to issuance of a Grading permit, provide offsite information to Albemarle County. Provide
an offsite ESC plan, if required, or an Agreement in lieu of a plan. Again, offsite borrow /waste site
information is required prior to Grading Permit issuance. (Rev. 2) Comment persists. Applicant response:
`Understood, offsite soil stockpile narrative note updated.'
4. Sheet C8: Note on Sheet C2 states that driveways are to remain until Phase 2 of construction. This sheet
(Phase 1) shows the sediment basin in conflict with the driveway. Revise to correct conflict.
5. Detail references on Sheet C8 appear to refer to incorrect detail or sheet numbers. Please revise.
6. Sheet C8 appears to have a stray SF symbol SW of Agnes Road. Clarify or delete.
7. Sequence of Construction does not mention the Stormtech system construction. Please include the
detention basin in the sequence of construction.
New (Rev. 1)
8. C8: DD is shown outside Limits of Disturbance (LOD). Show inside LOD, or expand LOD. (Rev. 2)
Comment withdrawn. Review error.
Engineering Review Comments
Page 10 of 11
9. C8: Phase 1 ESC shows proposed grading and utility (storm) system A that is to occur in Phase 2. Revise
Phase 1 to remove Phase 2 grading and utilities (storm pipe). (Rev. 2) Comment withdrawn. Review
error.
10. C9: Legend shows LOD. Show LOD on plan view using legend line -type. (Rev. 2) Addressed.
11. C9: SB primary riser and portion of principal spillway pipe are not visible; please show, consistent with C8.
(Rev. 2) Addressed.
12. C10: Show Phase 3 LOD on plan sheet. (Rev. 2) Addressed.
13. C10: Provide soil stabilization blanket (VESCH Std. & Spec. 3.36) between Rio Road E and retaining walls
at lower parking, ESC, Phase 3. (Rev. 2) Addressed.
D. Pollution Prevention Plan (PPP)
The PPP content requirements can be found in County Code section 17-404. This plan is disapproved, for
the reasons provided below.
1. If fueling will occur onsite, provide location and address it in the plan.
2. On the Phase 2 sheet, only 10 feet of width between the dike and edge of pavement is provided to the
dumpster, portajohns and rinse supply area. The extent of the RWD is not provided. Please clarify whether
that section of DD is RWD and that service trucks will not damage the dike. (Rev. 1) Addressed.
Applicant: `Note added to direct that RWD be properly maintained.'
3. Table in section C:
a. Show the location of the leakproof container for concrete washout.
b. Show dewatering sites on the plan, and relationship to E&S and/or PPP measures.
c. Show material delivery areas on the plans.
d. Solid waste disposal area is downslope of hill; stormwater from this location bypasses all
stormwater BMPs. Please show protection of the site from upland runoff and PPP measures for
leakage and spills.
e. Vehicle washing area(s) not shown on the plans. If the activity will occur, show on the plans how
the wash water will be handled. Detail for "Paved Wash Rack" (Sheet C11) shows wash water
draining to trapping device. Therefore, provide a trapping device in the vicinity of the construction
entrance. (Rev. 1) Addressed. Applicant: `Due to the slopes and the nature of the cut in this area,
we cannot provide a sediment trap. However, we have added a note provide a trapping device and
for wash rack runoff to be pumped into the sediment basin.'
f. Show a contractor laydown/storage area on the plan. (Rev. 1) Partially addressed. Asfollow-up:
PPP exhibit may show relic Phase 2 stockpile labels; please check /remove unintentional labels.
(Rev. 2) Comment withdrawn. Applicant response: `These stockpile labels are intentional, to
show reference to areas where stockpiling may occur. This guides grading of other lots, first.'
Additional:
Text image from 2/21/20 comment response letter, p. 7-8.
E. Additional comments provided by Frank Pohl
1. I don't recall seeing the proposed property lines on the drawings. Please show those as it will
help confirm if additional easements are needed, if they need to be adjusted, etc.
Property lines are now shown.
Engineering Review Comments
Page 11 of 11
2. l forgot to vcrify, plcasc include construction (sections 8.2 and 8.3 of DEQ Spec 9) and
maintcnancc (sections 9.2, 9.3, 9.4 and table 9.7). This project has a large number of rain
gardens, which is not typical, so additional notes is warranted.
These notes are now included (see last sheets)
3. Do the raingardens pass the 10-yr event without flooding into the streets? If not, additional
inlets to prevent flooding are required.
Rain gardens do pass the 10-yr event, updated HydroCAD analysis has been provided (SWM
calc packet pages 120-130).
The VSMP permit application and all plans may be resubmitted for approval when all comments have been
satisfactorily addressed. For re -submittals please provide 2 copies of the complete permit package with a completed
application form.
Engineering plan review staff are available from 2-4 PM on Thursdays, should you require a meeting to discuss this
review.
Process:
After approval, plans will need to be bonded. The bonding process is begun by submitting a bond estimate request
form and fee to the Department of Community Development. One of the plan reviewers will prepare estimates and
check parcel and easement information based on the approved plans. The County's Management Analyst will
prepare bond agreement forms, which will need to be completed by the owner and submitted along with cash,
certificates or sureties for the amounts specified. The agreements will need to be approved and signed by the County
Attorney and County Engineer. This may take 2-4 weeks to obtain all the correct signatures and forms.
Stormwater Management Facilities Maintenance agreements will also need to be completed and recorded. The
County's Management Analyst or other staff will prepare the forms and check for ownership and signature
information. The completed forms will need to be submitted along with court recording fees.
After bonding and agreements are complete, county staff will need to enter project information in a DEQ database
for state application processing. DEQ will review the application information based on local VSMP authority
approval. At this time, the DEQ portion of the application fees will need to be paid directly to the state. For fastest
processing, this is done electronically with the emails provided on the application. DEQ should notify applicants
with instructions on how to pay fees. When DEQ approves the application, they will issue a permit coverage letter.
This should be copied to the county.
After DEQ coverage is issued, via the coverage letter, the County can hold a pre -construction conference.
Applicants will need to complete the request for a pre -construction conference form, and pay the remainder of the
application fee. The form identifies the contractor and responsible land disturber, and the fee remaining to be paid.
This will be checked by county staff, and upon approval, a pre -construction conference will be scheduled with the
County inspector. At the pre -construction conference, should everything proceed satisfactorily, a joint VSMP and
grading permit will be issued by the County so that work may begin.
County forms can be found on the county website forms center under engineering;
hLtp://www.albemarle.org/dgptforms.asp?department--cdengmTo
WPO201900053 Ecovillage 040620_rev2