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Home My WebLink AboutWPO201600012 Approval - County 2016-04-07COUNTY 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 Approved Project: Landmark Aviation Hangar (VSMP) Plan preparer: Kent O'Donohue, L.A./Scott Kesecker, EIT / Balzer & Assoc. Inc. dodonohuekbalzer.cc 1561 Commerce Road, Suite 401, Verona, VA 24482; skeseckerkbalzer.cc Owner or rep.: Charlottesville -Albemarle Airport Authority 201 Bowen Loop, Charlottesville, VA 22911 Plan received date: 19 Feb 2016 (e -plan) (Rev. 1) 29 Mar 2016 (e -plan) Date of comments: 13 Mar 2016(e -review) (Rev. 1) 7 Apr 2016 e -review —Approved Reviewer: John Anderson WP0201600012 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. Revise Sec. 3/Construction Sequence Notes 7, 9 to include with County ESC inspector approval. (Rev. 1) Not addressed, but relatively unimportant. 2. Replace 11" x 17" ESC/SWM plan sheet inserts, if sheets revised. (Rev. 1) Addressed. 3. Sec. 6.G.l.a. —check here/elsewhere, please remove reference to separate project. (Rev. 1) Addressed. 4. Recommend coordinate with Airport Authority on any restrictions: hours of operation, site access, etc. (Rev. 1) Addressed. B. VSMP: SWPPP: Stormwater Management Plan (WP0201600012) VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This plan is approved. 30" Nyloplast MH inconsistent with VDOT Specifications (VDOT R&B Std., Vol. 1). If designer aware of VDOT approval of Nyloplast as VDOT-equivalent, please notify County. (p. 50, SWM Report; 16 Feb 2016) (Rev. 1) Addressed. Nyloplast structures #2, 4, & 6 have been changed to MH -2 VDOT approved precast structures. ST -1 added as well. Revised storm calc. sheets have been provided that reflect this change and plans have been updated. Nyloplast 48" DIA MH equipped with steps may be substituted* but recommend VDOT MH -1 (30" DIA too narrow). Site plan should follow VDOT standards (ACDSM, 6.A.1.), especially since Charlottesville - Albemarle Airport is a public use facility. County will consider Alt. to VDOT MH -1.* * Nyloplast 48" DIA MH may be used (structures # 2, 4, 6) at Landmark Aviation Hangar, provided: • Shown equivalent to brick /concrete (VDOT MH -1) • Nyloplast Str. details w/plans (link, below) Engineering Review Comments Page 2 of 3 • Installation Notes w/plans (Last p.) • MH equipped with steps (reqd.) • PE -Certification: Installation per design 2. Pipe slopes, p. 49 (Sfo), appear identical: 0.20. Please revise LD -347 (SWM Report; 16 Feb 2016). (Rev. 1) Addressed. 3. Bioretention /Level 2 (No request for revision): a. BMP surface elev. =600.00' b. 6" orifice elev. =600.50' c. 24" riser elev. =601.50' d. 1 -yr event peak elev. =600.60' @ 24.03 hrs e. 10 -yr event peak elev. =601.43 @ 12.68 hrs f. Ponded depth; time to peak, Acceptable. g. Bottom of sediment trap elev. =595.5' h. Bottom of bioretention stone elev. =594.67' (0.83' /Acceptable) 4. Energy balance QDeveloped, Allowable :S 0.8 x (QPre-Developed x RVPre-Developed)/RVDeveloped (9VAC25-870-66•B•3) (No request for revision; one recommendation) 16 -Feb SWM Report (HydroCAD); 1-31 event for DA A only evaluated. Typically, would evaluate all developed areas: A, B, C. `A'/pre- (0.87 Ac./No impervious); `A'/post- (1.39 Ac./ 0.76 Ac. impervious) `B'/pre- (0.29 Ac./ 0.11 Ac. impervious); `B'/post- (0.13 Ac./ 0.09 Ac. impervious) `C'/pre- (0.82 Ac./ 0.16 Ac. impervious); `C'/post- (0.45 Ac./ 0.16 Ac. impervious) Recommend confirm DA `C' Developed Imp =0.16 Aa. (ref DA maps) (Rev. 1) Addressed. Confirmed at 0.1588 acres. a. Qpre-D /A, B, C (cfs): 0.14 x x = ? b. RVpre-D /A, B, C (af): 0.026 x x = ? C. RVDeveloped /A, B, C (af): 0.012 x x = ? (DAs B, C: 1 -yr not evaluated) d• QDeveloped, proposed /A, B, C (cfs): 0.03 x x = ? (DA A: routed) e. QDeveloped, Allowable = ? i. May drop DAB C from Energy balance Eq. (runoff Vol/peak discharge for DA B, C developed < existing). Portions of impervious currently uncontrolled will be routed. ii. QDeveloped, Allowable <- 0.8(0.14)(0.026)/0.012 111. QDeveloped, Allowable C 0.24 cfs 1V. QDeveloped, Allowable > QDeveloped, proposed v. YES: 0.24 > 0.03; Acceptable f. Please Advise if QAllowable =0.24 cfs appears an error. SWM Report lists Q.,, =0.05 cfs. (Rev. 1) Addressed. 0.05 is correct. (3/22/16 comment response letter) Table 3: Pre- to Post -Developed Storm Rates after Detention Storm Event Flowrate cfs Pre Enemy Post Balance Max Q1 = 0.14 0.05 0.03 10 = 1.04 -- 0.78 5. Please label bioretention basin width, sheet C3 (W -22.4'). (Rev. 1) Addressed. 6. Please include VA DEQ Design Spec No. 9 / Sec. 8.2 / Installation notes to aid construction and inspection. (Rev. 1) Addressed. C. VSMP: SWPPP: Erosion Control Plan (WPO201600012) Virginia Code §62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan is approved. 1. Label OP dimensions, sheet C5 (L =9', W1 =3.75', W2 =10.25', D =?) (Rev. 1) Addressed. 2. SWM Report, p. 51 SCC #1, 2 -yr Vel. (4.63 ft/s) appears > 10 -yr Vel./p. 52 (1.71 ft/s) -please clarify. (Rev. 1) Addressed. Engineering Review Comments Page 3 of 3 3. Plan LOD =1.97 Ac.; SWPPP General VPDES Permit Registration Statement =1.80 Ac. Please reconcile. (Rev. 1) Addressed. 4. Recommend a second CE at Dickerson Road if construction access is via existing non -paved travel way, via Dickerson Rd (visible in image, below). If existing travel way is paved, please disregard comment. (Rev. 1) Addressed. Travel way is paved. 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 (received . 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; htt2://www.albemarle.org/deptforms.asp?departrnent--cdengMo Thank you / 434.296-5832 —x3069 File: WP0201600012—Landmark Aviation Hangar _VSMP-040716rev1 Approv