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Home My WebLink AboutSUB201400141 Review Comments Road Plan and Comps. 2014-12-19� OF A. kin ��RGt2314' COUNTY OF ALBEMARLE Department of Community Development 401 McIntire Road, Room 227 Charlottesville, Virginia 22902 -4596 Phone (434) 296 -5832 Fax (434) 972 -4126 Project: Fontana — Phase 4C, Section 1 & 2 Plan preparer: Terra Engineering and Land Solutions, P.C. Owner or rep.: Fontana Land Trust Plan received date: 7 Nov 2014 Date of comments: 19 Dec 2014 Reviewer: John Anderson Engineering has completed initial review of application SU132014 -141, Fontana —Phase 4C, Sections 1 & 2 A. Road Plan (SUB201400063) Note: Comments are general in nature since disapproval is thematic. More detailed comments may apply to future submissions, but detailed review at this stage is not possible given need to consider Phase 4C as an integrated whole (sections 1, 2, 3). A section 1 & 2 proposal does not work. The main reason for this is that Section 2 SWM is a proposed biofilter with pipe /ditch/yard systems conveying runoff from a portion of section 1 and nearly all of section 2 to this facility. Section 1 runoff is divided between section 2 and 3 SWM facilities. As an alternative, if the applicant coordinates with Planning and receives approval to plat section 2 (Lots 1- 11 /Belluno Lane RW) alone then Engineering may review Section 2 road plans. There are 2 options; one requires Planning approval: Phase 4C, Section 2 road plan, or a Phase 4C road plan with storm runoff provided by biofilter (sections 1 & 2), extended detention basin (sections 1 & 3), and additional measures that may be required to comply with 9VAC25- 870- 96/ -97. Drainage Area Map 1, Section 1 (Drainage Computations & SWM Report/4- Nov -14) shows: 1. 136 Ac. Post to Sect. 3 basin; 1.197 Ac. Post area to Hyland Ridge, uncontrolled; 0.533 Ac. Post to Sect. 2 Basin. Drainage Area May 6, Section 2 (Report/4- Nov -14) shows: 4.056 Ac. Post to Luxor Pond (via bio- filter); 1.312 Ac. Post to Hyland Ridge (uncontrolled). Planning must confirm a final plat of Sec. 2 that excludes sections 1 & 3 is an administrative possibility. Note preliminary plat covers all 3 sections. Planning comment (1 -Dec) highlights the need: "The title of the road plan reads: "Fontana — Phase 4C, Sections 1 & 2 "; however, when reviewing the plan it appears to cover all 3 sections. Notably Brunello Court is depicted on sheet C2.1, and Belluno Lane is depicted throughout various sheets. Please address this inconsistency." Comments 1. Road plans must provide adequate SWM facilities for storm runoff increase. Please submit WPO/VSMP Applications, either for Phase 4C, Section 2 (biofilter), or entire Phase 4C. Note: Engineering preliminary plat comment, 7- Nov -14: "preliminary review of extended detention SWM facility indicates proposed (or similar) design could provide 2xWQV (210.9cy x 2) needed to treat 113,256 SF impervious, 292,426 SF turf runoff (post- development- /section 3, portions sec. 1) if basin depth = 4.6'(f), x- sectional basin area 2.3' above floor = 2,475SF. Statement does not indicate SWM plan or basin design approval. ACCD will furnish supportive detail. It is imperative that design consider: direction of section 1 runoff, and whether runoff is routed to section 2 bio - filter, to section 3 extended detention basin, or is uncollected (front of Lots 16, 17, 18; essentially all of Lots 12, 13)." 2. Ref. 14 -409, Planning comments on road plan (sent as email, 18 -Dec; Also available in County- View): "[14- -409, 14 -410, 14 -411] The Cascadia Connector is depicted on sheet C2.1 and is designated as Engineering Review Comments Page 2 of 3 being 12' w/ 4' shoulders, 50' R/W. As depicted this road design does not meet the requirements of the ordinance which dictate it to meet VDOT standards (per section 14 -409, 14 -410, and 14 -411). Please work with VDOT, Engineering, Planning, and Fire & Rescue to assure this connection is designed appropriately. Revise." Engineering concurs with Planning comment request for revision; please provide Cascadia Connector design. Ref. VDOT road design manual. 3. Recommend FH, cul -de -sac Belluno Lane since distance from hydrant on Via Florence to Lot 5 residence is 620' (f). 4. 42.75 LF 18" DIA pipe (inlets D4 - D3) is less than minimum 0.5% slope; please revise. 5. P. 31, Report: slope of pipe, YD to pond, is 0.33% ( <0.5% min.); please revise. 6. C3.5 —there are two details #3 — please renumber one or the other. Advance WPONSMP comments Please REF email, October 31, 2014 5:12 PM, ACCD to Terra Engineering: "of relevance- 1. Please use, complete, and include the (Attached) SWPPP template, with VSMP (WPO) Application 2. Attached: Application review process diagram. This process reflects adoption of revised County Code, Ch. -17, Eff. 1 -Jul -2014 3. Attached: VSMP Permit Application form, with fee schedule 4. Link, Additional VSMP resources: http:// albemarleengineer .blogspot.com/2014_10 01 archive.html 5. Link, VPDES Registration Statement: http: / /www.deg.vir i� nia.gov/Portals /O/DEO/ Water / Publications /CGPRegistrati2nStatement2Ol4.p df 6. Relevant sections of Albemarle County Code: § 17- 104.B.; §17 -400, - 401, 402, -403, -404, -405; § 17 -412; § 17 -417 [other sections may apply]" 1. SWM hydrologic modeling must utilize TR -55 (MRCS) 24 -hr distribution rainfall in SWM design. Rational, modified rational, and/or Manning equations, while acceptable for pipe /ditch conveyance system design, are not acceptable for SWM facility design [9VAC25- 870- 95.General, B.]. [Phase 4C, Sections 1 and 2, Drainage Computations and Stormwater Management Report, November 4, 2014] Also, please use curve numbers (CN) in hydrologic calculations consistent with NRCS, rather than runoff coefficients (C /rational formula). 2. Ref. item #6, 31- Oct -14 email, above —with emphasis on Sec. 17 -403 (documentation demonstrating compliance), 17 -404, (PPP), 17 -405 ( SWPPP), and 17 -4052 (ESCP). 3. VDOT approval is required. Please furnish VDOT LD -204 (stormwater inlet computation sheets), and LD -229 (storm sewer design computations) or required information in equivalent (table) format. Engineering cannot evaluate inlet systems based upon Drainage Computations and Stormwater Management Report (4 -Nov, 2014) alone. VDOT comments on road plan design will be forwarded when received. 4. Email -Wed 10/29/2014 12:21 PM —ACCD to Terra Engineering: "If a WPONSMP application for section 1 and 2 is submitted prior to section 3, please note that natural and final contours (back yards, Lots 14 -18) direct a portion of post - development runoff to the proposed extended detention basin. This basin treats section 3, primarily, but also receives section 1 runoff. In effect, WPONSMP applications for all sections should be coordinated for near - simultaneous submission. There is no advantage to the owner in splitting sections (though I will review and comment on section 1 and 2 separately) since there is no feasible way to authorize land disturbance in section 1 without also obtaining section 3 WPO approval." As stated at the outset in this letter, sections 1 and 2 do not work from a WPONSMP Application perspective, without section 3. 5. Report does not lend itself to easy comparison of design against water quality standards found at 9VAC25- 870 -96 / -97. Similarly, a straightforward, (hydrologic) model - supported demonstration of pre- /post - developed 2 -yr and 10 -yr events for comparison with water quantity requirements is not included or easily identified in the Report. It is important and necessary to include: TR -55 graphical peak discharge method, or TR -55 tabular hydrograph method (VSWMH, First Edit., 1999, Vol. 2); explicit reference to Water Quality BMP Pollutant Removal efficiencies (VSWMH, 5 -14, p. 5 -106 [bio- filter /section 2]); and Appendix 5D worksheets needed to determine: which water quality regime Engineering Review Comments Page 3 of 3 applies (9VAC25- 870- 96.B.1 -4); post - developed pollutant load; and, load reduction achieved by the proposed bio- filter and extended detention basin. This information, if implicitly included with Report, is elusive. Design must reflect procedures found in the VA Stormwater Management Handbook (VSWMH). Please make explicit connection between design, standards found at 9VAC25- 870- 96/ -97, proposed SWM design, and VSWMH. Although other design methods yield useful information, for purposes of VSMP Application review, procedures found in VSWMH are source of reference. It is difficult to evaluate design or calculated data contained in the report against compliance requirements that are prerequisite to WPO/VSMP plan approval. Please feel free to schedule a plan review meeting to discuss road plan or WPO/VSMP Application requirements for Fontana, Phase 4C. tel - 434.296.5832 — x3069. File: SUB201400141- fontana4C -sect 1 & 2 road- 121914.doc