HomeMy WebLinkAboutWPO201600027 Review Comments WPO VSMP 2016-05-21COUNTY OF ALBEMARLE
Department of Community Development
401 McIntire Road, Room 227
Charlottesville, Virginia 22902-4596
Phone (434) 296-5832 Fax (434) 972-4126
Project:
Plan preparer:
Owner or rep.:
Plan received date:
(Rev. 1)
(Rev. 2)
Date of comments:
(Rev. 1)
(Rev. 2)
Reviewer:
WP0201600027
VSMP Permit plan review
Wildrock VSMP
Keane Rucker /Justin Shimp, Shimp Engineering, 201 E. Main St.
Suite M, Charlottesville, VA 22902 [iustin(a)shimp-enizineering com]
Heartrock Family Farm LLC, 2521 Summit Ridge Trail
Charlottesville, VA 22911
15 Apr 2016
6 May 2016
20 May 2016 (e -submittal)
23 May 2016 (print submittal)
25 Apr 2016
15 May 2016
21 May 2016—Provisionallypproved
John Anderson
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.
1. Provide SWPPP, as with past projects. Template Attached. (Rev. 1) Addressed. Asfollow-up, include
ESCP insert (inset) that shows full extent of LOD (Sec. C, New item #7, below.) (Rev. 2) Addressed.
2. Also: revise General VPDES Permit Registration Statement to reflect rev. LOD =5.8 Ac. [With Applicant
permission, county can make and initial this change.] (Rev. 2) Addressed.
3. With Applicant permission, county can revise Registration Statement to include email contact addresses.
Without email, VDEQ correspondence is constrained to letter delivery (Anticipate significant delays).
[Recommend registration statement list: carol In sw a,comcast.net and justinAshimp-enaineering.com ] (Rev. 2)
Addressed.
B. VSMP: SWPPP: Stormwater Management Plan (WP0201600027)
VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This plan is
PROVISIONALLY -approved. Please ensure SWM Plan (print version X 4 copies) +SWPPP insert submitted Monday,
23 -May reflect deletion, addition, or revision outlined below, or in Applicant response letter. All remaining revisions
are clerical; they do not affect SWM design, or compliance. Please call if any questions. Very well done, Keane.
VSMP Plan (booklet) d. 15 -Apr 2016 contains: cover letter; VRRM Re -development spreadsheet; VDOT
LD -268, post -development t,/runoff calculations for ditch /culvert -sizing (Rational Method); post -
development drainage map; soils data; NOAA precipitation frequency. It does not contain: Q1, -2, -10
analysis based on SCS 24 -hr TR -55 model; SWM design based on 9VAC25-870-66.B.3. (channel
protection, i.e. energy balance), 9VAC25-66.C.1 or -66.C.2 (flood protection -discharge to systems that
Engineering Review Comments
Page 2 of 5
currently experience, or do not experience localized flooding); or SWM water quality design based on
9VAC25-870-65. Please provide SWM design based on 9VAC25-870-65 and 9VAC25-870-66. Note:
one -paragraph mention of design without water quality or water quantity design elements is without parallel,
and startling. It is atypical of Shimp Engineering plan submittals, and surprising. Engineering and Planning
have been in contact with Applicant since Jan -2015. Project site plan, VSMP, and special permit expense
may end any chance this project will be built, and we implore complete design submittal that reflects VSMP
plan requirements. We encourage close examination or consideration of:
a. 9VAC25-870-66.D. —"If all runoff from the site is sheet flow and the conditions of this subsection
are met, then no further water quantity controls are required."
b. Ref. discussion /email (J. Anderson -Justin Shimp) on 19 -Apr: Water quality compliance that relies
on forest/open space in post -developed condition requires deeded restriction and easement plat.
This is an option. Alternatively, re-examine VRRM re -development site data land cover acreage.
28.26 Ac. is invalid; it exceeds parcel acreage. Unless Applicant places 23.97 Ac. in restricted
covenant easement (forest /open), site data requires revision. Engineering recommends:
i. Examine effect of reduced site area (revise site data tab).
ii. Calculate Area of proposed trails (stone/mulch/soil) north of existing structure; tabulate
areas. Mulch and soil are pervious. Do the same south of existing structure. Tabulate.
Engineering requests: N/S Trail pervious /impervious surface chart /table. Do not include
these areas in VRRM .xls. County recognizes that network of narrow crushed stone and
primitive walking trails to access remote or central areas at Heartrock will not result in
changes to the predevelopment runoff characteristics of the land surface after construction
and stabilization are complete. Sheets C3 /C4 show pre- /post -developed areas. It
appears design proposes equivalent (or slightly less) impervious area than currently
exists. Revise VRRM .xls and design, accordingly.
iii. If off-site nutrient purchase is selected, we urge consideration of on-site features that may
minimize total phosphorus load reduction required.
iv. If on-site BMPs are required /selected, we urge consideration of any practice that may
minimize scale of on-site best management SWM facilities; for example, dissipate ditch -
line flow via series of turnouts to level spreaders that convert concentrated flow to sheet
flow. If BMPs are required, please consider simpler practices —dry or wet swales, for
example, near parking areas. The county seeks to minimize Applicant design
/construction expense, and urges minimum approach to design.
v. VRRM .xls requirements may be reduced by treating 14' W gravel site access as a linear
design element ydesign Q1 ditch runoff does not reach stream to east, or concrete ditch
northeast of site. If design uses series of timber level spreaders or equivalent, VRRM
phosphorus load reduction requirements (BMP, or nutrient purchase) may be minimized.
Applicant response, cover letter d. 6 -May 2016: "The VMSP Plan Booklet has been completely overhauled."
Given this, consider comments above less relevant than comments that follow. (Disregard comments, above.)
1. Note: While SWM strategy has been discussed and is accepted, revised submittal presents several review,
design, or data gaps. (Rev. 2) Addressed.
2. It is important, given strategy that relies on directing a portion of on-site post -development runoff to a level
spreader, with no other BMPs necessary, to provide clear path to understanding.
Please provide:
a. TOC:
i. With pre -development SWM Map, provide TOC (listed as 25.2 min, elsewhere.) Ref.
post -development SWM Map. (Rev. 2) Addressed.
Engineering Review Comments
Page 3 of 5
ii. With pre- /post -development SWM Maps (with maps, or separately) list: time of
concentration for overland, shallow concentrated, and concentrated flow. (Rev. 2)
Addressed.
iii. Provide TOC calculations, not simply values. TOC nomographs provide overland TOC
(pre- TOC =11.4 min; post- =14 min). Kirpich logarithmic chart may be suitable for pre-
/post- regimes, but appears misapplied. 1,240' is an extreme value for shallow
concentrated flow path length. A reasonable limit (L') for shallow concentrated flow is
500'. [Ref. VESCH example, p. V-39; link:
http://vA w.deq.vir ing ia.gov/Portals/0/DEQ/Water/StormwaterManagement/Erosion Sediment Co
ntrol_Handbook/Chapter%205.pdf ] Also, post -development flow is concentrated once it
reaches site access /travel way ditches. It seems post -development concentrated flow
may be reported as shallow concentrated flow. Revise to more nearly reasonable TOC
values; use rev. values wherever needed. (Rev. 2) Addressed.
b. Energy balance:
i. Provide TR -55 graphical methodology for RV values. Using composite (weighted) curve
numbers that reflect soil type infiltration and ground cover, calculate runoff depth (RV)
and runoff volume in watershed -inches (Q) required to support energy balance equation.
Ref. VESCH 1992, pg. V-34, etc. Values used in energy balance are for the moment
unsupported. Encourage .PDF preview prior to resubmittal of SWM calculations booklet
/VSMP Plan. (Rev. 2) Addressed. Ref. p. 11, 13 of Calc. booklet [5/20/2016 6:01 PM
email .PDF Attachment] available County View (CV) viewable project -related .PDF.
Ima¢e (Calc. booklet /p. 8)
Wildrock Energy Balance Equation
24 Hr 1 year Storm:
Qdeveloped:� I•F• Qpre-developad RVPre-oeveloped) Redeveloped
(!31
"W evelaped:5 Qforested RVfo rested Redeveloped
Drainage Area : nn
Qpre-developed — x•72
RVPre-Developed = Ceveioped = 1.22 dfS
RVDeveloped
Qdev must be below pre -developed conditions. Qdev effective max = 0.72 cfs
c. Culvert and Ditch Flow C __ _ions (Calc. booklet)
i. TOC, culvert E (site entrance): Ref. ditch 5, only. Ditch 5 flow comprised of limited
shallow concentrated flow with near immediate transition to concentrated flow (grass
channel). Revise TOC, culvert E. 22.3 Min. is too high. (Rev. 2) Addressed.
ii. Include culvert F & G in calc. booklet, since included with plan. (Rev. 2) Addressed. As
follow-up, please remove culvert G pipe outlet data from plan sheet C5 since culvert G
(carryover from an early concept plan) will not be used.
iii. Label ditches L-6., sheet C4. (Rev. 2) Partially Addressed. Provide explicit plan sheet
Note: "See Exhibit, p. 21 of Calc. booklet under cover d. May 20, 2016, viewable in CV
and project files. Also, see Final Site Plan SDP201600014, Sheet No. _ " [fill in blank].
County recommends but does not require p. 21 Culvert Exhibit be included with VSMP
plan set.
iv. TOC to level spreader (LS) reported as 23 Min. Revise LS TOC (23 minutes) unless
distance (140' f)/velocity, grass channel/ditch 6 =6 minutes. It would appear to take <1
min. (3.33 fps /LD -268) (Culvert C & D TOC =17 min.) (Rev. 2) Addressed.
Engineering Review Comments
Page 4of5
3. Title Sheet: Add SWM Narrative, the visual equivalent to (as prominent as) other title Notes. Include
reference to Calc. booklet /booklet date. Address water quantity/quality through VSMP Plan, not booklet
only. It is vital to include reference to Level Spreader "depicted on C4" as a "SWM -associated permanent
site measure (though not a BMP)." ESC measures are removed once upslope areas are stabilized. The
Level Spreader will not be removed, ever, and must be maintained. Albemarle County is not requesting
SWM bond or maintenance agreement for this measure. A level of practical oversight and implicit faith and
trust in Applicant affect decisions. (Rev. 2) Partially addressed. As follow-up, please replace last
sentence of SWM Narrative with: "The level spreader, a velocity -attenuating permanent site measure, must
be appropriately maintained. In design and performance, the level spreader supports a strategy discussed
and accepted by Engineering. It is not a (Part IIB) BMP but is accessory to SWM compliance strategy.
Not strictly a Part IIB best management practice SWM facility, the level spreader does not require a SWM
bond, or stormwater maintenance agreement. Overall site design and strategy support this approach."
4. Approach to compliance (discussed at length with county) revolves to a degree on LS design. To this end,
we recommend conservative design; for example: concrete footer beneath 6 X 6 treated timber that extends
below frost line to ensure 0° slope. If settling distorts level placement, there is potential for erosion expense
for downslope play-scape and trail features. (Rev. 2) Addressed.
5. LS detail reference to `detail 4 on sheet C5' points to construction entrance detail; revise. (Rev. 2)
Addressed.
6. Although LS detail is a standard detail, detail may benefit from direction of flow arrow. (Rev. 2)
Addressed.
7. It is county hope and intent to approve this plan with next submittal. To this end, please call if any
questions. .PDF preview of plan sheets, calculations, booklet, and SWPPP are welcome. (Rev. 2)
Addressed —ref. email sent with Provisional VSMP Plan Approval, 21 -May 2016, 2:20 PMf.
C. VSMP: SWPPP: Erosion Control Plan (WPO201600027)
Virginia Code §62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan is approved.
1. C2 Include demolition in sequence of construction; existing site access or parking that will be removed,
for example. (Rev. 1) Addressed.
2. C3 —Show existing features to be removed (TBR). Consider ESC for items TBR, as necessary. (Rev. 1)
Addressed.
3. C3 —Label existing rectangular shaded features (existing parking?). Label surface material of these features.
(Rev. 1) Addressed.
4. C4:
a. Show trees/tree lines (compare with C3). (Rev. 1) Addressed.
b. Show all proposed grading. Ref. culverts F/G, for example: no grading shown at these locations.
(Rev. 1) Addressed. As follow-up, see New item #8, below. (Rev. 2) Addressed.
c. Label Area of Disturbance —4.68 Ac. (Rev. 1) Addressed. (5.8 Ac.)
d. Though Site Plan identifies features, please label: overflow parking; parking area surface type;
building footprint dimensions (i.e., impervious area); access width (14'); circular features;
walkway/trail width/surface type; etc. There is a general lack of descriptive information.
Reviewers need to understand site without needing to refer to Site Plan. (Rev. 1) Addressed.
5. C5 —Show sediment trap profile, not just VESCH plate image. Show existing grade/ground elev. in profile.
(Rev. 1) Not addressed. Also, New item # 8, below [request intended in part to reduce or eliminate error].
(Rev. 2) Addressed.
New
6. C3: Remove Limits of Disturbance from Existing Conditions plan sheet, except as outlined in item #4,
below. (Rev. 2) Addressed.
Engineering Review Comments
Page 5 of 5
7. C4: Provide inset (scale 1"=150' or 100') that shows full extent of LOD. Transfer image from calc. booklet
post -development SWM Map to C3 (there appears to be space on C3). With this C3 image, label: "Gravel
road to be converted to turf' for LOD prongs leading off -sheet (development maps) since it appears gravel
roads in each area will be converted to turf Display this label prominently with image on C3. Full extent
of LOD should be shown on plans. Also, include Note on C3 (image) that references C4, the ESC Plan for
this project. (Rev. 2) Addressed.
8. C4/C5 —Sediment Trap: check A, B, C elevations (109, 111, 114) against C4 (inconsistent site elevations).
Ensure proposed (trap) contours accurate; for example: floor and downslope berm elevations. Tie proposed
contours to existing contours to aid review, ESC bond estimate, and construction inspection. (Rev. 2)
Addressed.
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 request a pre -construction conference by completing a 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;
htW://www.albemarle.org/deptforms.asp?department--cdengMTo
Thank you -434.296-5832 —x3069
File: WP0201600027 Wildrock 052116rev2