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Home My WebLink AboutWPO202100041 Approval - County 2021-12-17t� OF ALB County of Albemarle COMMUNITY DEVELOPMENT DEPARTMENT ��BGIN�Q' VSMP Permit Plan Review Project title: HTC Area C Townhomes — VSNIP Project file number: WPO2021-00041 Plan prepares Shimp Engineering, 912 E. High St., Charlottesville, VA 22902 Keane Rucker, FIT, keane(a),shimp-engineering.com Justin Shimp, PE, Iustin(d,)shimp-engineering.com Owner or rep.: Post Office Land Trust, ArmMae Holdings LLC Charles Wm Hurt and Shirley L Fisher, Trustees charlie(i�virginialandcompany. com P. O. Box 8147, Charlottesville, VA 22906 Plan received date: 16 July 2021 (Rev. 1) 28 Oct 2021 Date of comments: 8 Sep 2021 (Rev. 1) 9 Dec 2021 (Rev. 1/update) 10 Dec 2021, Email addresses C.l.c.i. MEMO DATE: 17 Dec 2021 - Approved Reviewer: John Anderson 401 McIntire Road, North Wing Charlottesville, VA 22902-4579 Telephone: 434-296-5832 WWW.ALBEMARLE.ORG County Code section 17-410 and Virginia Code §62.1-44.15:34 requires the VSNIP authority to act on any VSMP permit by issuing a project approval or denial. This project is approved. 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 title of SWPPP to include ref, to WPO202100041 (Rev. 1) Addressed. 2, Update ESC-SWM I I" x 17" plan sheet inserts, if /when revised. (Rev. 1) Addressed, B. Pollution Prevention Plan (PPP) —Approved The PPP content requirements can be found in County Code section 17-404. C. Stormwater Management Plan (SWMP) VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This plan is approved. (Rev. l) All 8-Sep review comments except item l.c.i are addressed with revised 28-Oct VSMP plan. 1. Cl a. Revise plan and SWPPP title /cover sheet include reference to WPO202100041, b. Replace Stormwater Management Note first sentence with these two sentences: "Per the approved ZMA200200002 and Approved SWM plans, runoff will be directed to existing regional stormwater facilities designed for a full buildout of each site. Reference Engineeringftle 2301, Hollymead Town Center, regional SWMI for block II SWM facility design (adjacent to Rt. 29), and SWM2 for block III SWM facility design (west of Laurel Park Lane). Engineering Review Comments Page 2 of 4 c. Despite Storrnwater Management Note that states `Both facilities, as well as the offsite storm pipes which coney runoff into them, were designed for a maximum of 85% impervious cover....' provide LD-229 storm pipe computations and LD-204 storm inlet design data tables that consider total watershed full build -out runoff reaching offsite storm pipes.' It is unclear that existing storm pipes are designed for total watershed full build -out. It is important to evaluate effects of routing additional runoff to existing pipe networks. i. In the case of Area C, block II, proposed on -site 1-522 18" HDPE connects with Ex. 18" RCP (C7) at Connor Drive. (Rev. 1) Persists. Applicant response (letter d. 28-Oct 2021): `This is now addressed in the SWM plan sheet C20. Specifically, we analyzed all site outfall points (C 1, D2, D 1, 130) to demonstrate compliance with our best estimate of the HTC storm sewer design parameters. We included a factor of safety for the original estimates by estimating that the original design for this site was 5% less impervious than the design of the overall watershed drainage area. Even with this factor of safety included, we are confident that this development's peak runoff (shown as C * A) is less than each storm sewers' original design. Due to this we will proceed with the submittal. Please reference Sheet S 1 "SWM & BMP Plan" from WPO2003-02301 "Hollymead Town Center Regional Service Area C" included with this submittal. We will continue to search for the originals storm channel designs (LD-229, for an easy direct comparison, as was done for Block III below), but we are confident this development design routes runoff into the existing system at rates that comply with the original design, thus satisfying channel protection and flood requirements.' As follow-up: Please ref. LD-229, C 19, Al to AO, which indicates block II runoff consumes 77% (13.42cfs of 17.4cfs) of 18" DIA (1.62%) pipe capacity. At Str. AO, development discharge joins existing runoff within existing storm sewer system. C7 shows 18" RCP (127.6') conveys the combined (existing + block II) runoff from Str. A0. Please evaluate effect of combining Qio peak block II runoff, 13.42cfs, with existing peak flow at Str. AO to ascertain whether pipe network below Str. AO is adequate to carry block II peak runoff. Please confirm existing peak Qio flow within existing pipe network at structure AO. Quantitative analysis is requested. (Rev. 1/update) Addressed. Email, Applicant (December 10, 2021 2:09 PM): `This is correct, no other pipes enter All, I confirmed this in my site visit in October.' Email, Albemarle (December 10, 2021 2:03 PM): `Please confirm Str. AO receives flow from pipe Al -AO, and inlet at AO, only. If that's the case, then, thanks, no further analysis requested. If additional pipes enter Str. AO, then provided AO-BO has sufficient capacity for the Q 10 event, we ask nothing else.' ii. In the case of Area C, block III, proposed on -site 15" HDPE connects with Ex. 24" RCP (C8) at Lockwood Drive. (Rev. 1) Addressed. Applicant response: `This is now addressed in the SWM plan sheets. Specifically, we analyzed the site outfall point (AO) to demonstrate compliance with the original HTC storm sewer design parameters. It is compliant. See included "SDP2005-00019 Abington Place — Phase F (specifically, sheet S11) included with this submittal.' 2. C2 a. Label Connor Drive east of Timberwood Blvd. b. Recommend a label to clarify that Area of block C north of Connor Drive and Timberwood Blvd, east and adjacent to Berkmar Drive Ext. is not included in WP0202100041. c. Identify regional SWM facilities as SWMI and SWM2. 3. C5, C6 a. Revise sheet title to read Site Layout, rather than Site Plan, A WPO plan does not approve a site plan. 4. C7, C8 a. Revise Conner Drive to read Connor Drive, 5. C9 a. Name roadway network (streets /Orchid Bend). 6. C11 Engineering Review Comments Page 3 of 4 a. Road profile will be evaluated with HTC Area C Townhomes ROAD plan. Please submit ROAD Plan at earliest convenience. b. Revise block II road & WL profile captions (since identical). c. Check block III structure profile labels Note: 2 A2 labels); please revise. d. Check /revise block II storm profile captions, as needed (Profile Al-A7). e. F3-A7 profile: provide label /note specifying subgrade compaction for pipes /structures. Entire pipe -structure network is in fill. D. Erosion and Sediment Control Plan (ESCP) Virginia Code §62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan is approved. 7. C14 a. Acquire offsite temporary construction easement to construct stepped retaining walls, if needed, TMP 32-43. (Rev. 1) Addressed. Applicant response: `An offsite temporary construction easement will not be necessary for the stepped retaining walls as the walls will be constructed from above.' b. Please remove extraneous linework that may be mistaken as a third (stepped) retaining wall, this linework crosses DD, proposed grade, and a feature that is unknown. Eliminate linework unless relevant to ESCP Phase 1. Highlight yellow, image, bolo . (Rev. 1) Addressed. [image/s removed with Rev. 1 comments.] c. During HTC hotel construction downslope in the same development, a sediment trap (sized per VESCH) positioned near the edge of the hotel development failed on several occasions. In that instance, sediment -laden release to neighboring parcels following storm events proved resistant to remedy. Experience of failed attempts to modify a trap with limited offset distance to property line is sufficient basis for Engineering to request additional volume for STI, ST2. Any failure of either ST will result in release of sediment -laden discharge to Connor Drive, existing storm inlets, and ex. storm network. Note: proposal to use existing culvert as sediment trap 1 outlet is virtually identical to proposal at HTC hotel, where this approach failed. Gig image, below[ HT-C e __a G Meek, 11 tin a_.._i,....... ent blue ,.:_,a_ left. hotel ST bit._ ^:_ [image/s removed with Rev. 1 comments.] (Rev. 1) Addressed. Applicant response: `Noted, this is an agreeable request, with the trap location in a developed and heavy -trafficked area, in an equivalent situation to a location with documented trap failure. Both STI and ST2 have been oversized by 15% to prevent sediment trap failure on block II.' Process: After approval, plans will have 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 have to be completed by the owner and submitted along with cash, certificates or sureties for the amounts specified. The agreements will have to be approved and signed by the County Attorney and County Engineer. This may take 24 weeks to obtain all the correct signatures and forms. Stormwater Management Facilities Maintenance agreements v 11 also havo to be ,.,... pleted and are recorded. TIC Engineering Review Comments Page 4 of 4 After bonding and agFeements aFe is complete, county staff will enter project information in a DEQ database for state application processing. DEQ will review the application information based on local VSW authority approval. At this time, the DEQ portion of the application fees will have to be paid directly to the state. For fastest processing, this is done electronically with the entails 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 must 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 VSNIP 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 Applications: httos: //www.albemarle. org/govemment/communitv-develonment/aooly-for/engineering-anol ications Thank you. Please call if any questions — tel. 434.296-5832-x3069, or email 4anderson2(a_)albemarle.ora. WP0202100041_HTC Area C Townhomes_121621_approv.doc