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HomeMy WebLinkAboutSDP201900067 Correspondence 2020-04-02 (4)SHIMP ENGINEERING, P.C. Design Focused Engineering April 2, 2020 John Anderson County of Albemarle Department of Community Development 401 McIntire Road, North Wing Charlottesville, Virginia 22902 RE: SDP 2019-00067 Eco Village Charlottesville — Engineering Comment Response Dear John, Thank you for your review of the Final Site Plan for Eco Village. We have revised the plans per Tim's comments dated December 6, 2019. Our responses are as follows: GENERAL 1. Address WPO Plan review comments sent 12/4/19 (WPO201900053). WPO Plan approval is required prior to Final Site Plan (FSP) Approval. Noted. Will continue to work in tandem. 2. If project is to be subdivided, SWM Facility, SWM Facility Access, and public /private drainage easements may be recorded with the subdivision plat, meaning, once WPO Plan is approved, SWM Facility Maintenance Agreement is recorded, VAR10 (DEQ) VPDES permit issued, and WPO Plan bonded, the project is eligible to receive a Grading Permit (eligible for pre -construction). Also: see items 28 and 45. Noted. Property is to be subdivided per updated boundary info. 3. Submit Road Plan and Private Street Authorization request at earliest convenience. Engineering defers to Planning Division on Private Street request, yet is involved and reminds Applicant of code requirements at 14-234 if making private street authorization request. Engineering will support request, given density and comprehensive plan goals, and prior Ecovillage special use permit and initial site plan approvals (SP2018- 00016, SDP2018-00056, respectively), which reflect design consistent with planning goals. Nevertheless, private streets are subject to VDOT design standards /specifications, Albemarle County Design Standards Manual guidance, and Drainage and Road Plan Checklists for plan reviewers. Please submit Road Plan with Application, with minimum number of print copies (or digital road plan) as soon as possible. Roads must be built or bonded prior to Final Plat approval. Road plan must be approved prior to FSP approval. Road plan has been submitted. Since this street serves attached dwelling units, the private street authorization request can be approved by the planning agent, and is included with this submittal. 4. FSP is subject to SP201800016 and SDP201800056 conditions /conditional approval requirements. Engineering defers to Planning concerning interpretation or effect of these approval documents. Noted, this is reflected in the site plan design. C1 5. Slopes Note: Provide LS name /date that 9,866 SF of preserved slopes overlay was surveyed less than 15 %. A 912 E. High St. Charlottesville, VA 22902 1434.227.5140 1 shimp-engineering.com 6. Provide related plan references: SP201800016, SDP201800056, WPO201900053, SUB2019-XXXXX (Road Plan). Referenced on C I. 7. Provide description of any steep slopes waiver granted, with reference to legislative action. Provide details of waiv(- r exemption to disturb steep slopes. Added on new Sheet C3 (no room on C1) 8. Provide copies of detailed PE -sealed geotechnical retaining wall designs for wall ht. > 4' max. associated with parking or any road /travelway prior to FSP approval. See Final Site Plan checklist for plan reviewers, p. 1. Also Retaining Wall Plan checklist; Attached. None of these walls are required for Road Plans, we will provide with next final site plan submittal. C2 9. Show /label preserved steep slopes on TMP #61-210B. Applies to additional sheets; C17, for example. Steep slopes shown. 10. Label stream buffer (TMP #61-210B). Stream buffer shown. C3 11. Label typ. parking stall depth and width, all parking areas. For perpendicular radial (curvilinear) parking, label stall width `at narrowest point along the length of the space.' (18-4.12.16.c.4.) Noted. Dimensions added. 12. Label HC-parking space width (2 separate locations). HC space width added. 13. Revise Road A 32' Private to clarify that paved surface is 20', not 32' Noted. 14. Similarly, revise Road B, C, D, 30' Private to clarify width of geocell pavers (vs. 30' easement width). Noted. 15. At relevant points along Road D, label radii. (See Roads B, C.) Noted. 16. Provide VDOT GR-2 guardrail on south side of lower parking lot for any parking space fronting retaining wall, or space facing a grade of -3:1, or steeper. Provided. 17. Label 10' Multi -use pedestrian trail. Noted. 18. Label 14' Emergency Fire Access. Noted. 19. Provide CG-6 (curb with gutter) to match VDOT Road Design Manual typ. CG section in urban setting, not CG-2. Provide CG-6 for Road A between Rio Rd. E entrance and the 4 perpendicular parking spaces just north of the 2 HC- parking spaces on west side of Road A, thru R5' radius return. CG-2 does not meet VDOT standard for urban design; please revise to VDOT standard. Also, 18-4.12.15.g. CG-6 provided at critical points along Road A in accordance to what we identified as the spirit of your request, specifically along the lower parking area, along the point where most of Road A runoff is located, and before/at the intersection with Rio Rd E. 20. Provide CG-6, continuous from point identified in item 19., through last curvilinear parking space (End of Road A). CG-6 is not provided here due to the low amount of runoff, since it is the top of a hill. 21. Provide CG-6, not CG-2, in all parking areas. Ref. 18-4.12.15.g. No exception appears to exist under Resolution adopted May 1, 2019 (SP201800016), or special permit condition 3., which reads (in part): `Improvements related to stormwater, drainage, and grading shown on the final site plan and water protection ordinance plan for Ecovillage Charlottesville shall be in general accord with the same improvements and grading shown on the "Stormwater Improvements" exhibit and "Proposed Entrance Layout" exhibit prepared for SP201800016 by Shimp Engineering, P.C. and dated 2/4/2019 and subsequently revised 2/27/2019, inclusive of additional modifications as noted in a. — c. below, and to the satisfaction of the County Engineer.' CG-6 is required to meet ordinance design requirements for parking, and VDOT typ. section for subdivision roads. We have provided gutter for curb along spaces that see more than 0.1 ac. drainage area. The current design achieves the goal of well -managed overland runoff. We would be glad to review and discuss with engineering with a phone conference as we seek to find solutions acceptable by both parties to this non- traditional development. 22. Recommend Site Summary include Ref. to WPO201900053 1.26 Ac. Forest /Open Space Easement. Noted, (area is now 1.06 ac) 23. Label 12' and 14' turnaround W (narrowest) and L dimensions, to clarify, and avoid misunderstanding. Dimensioning clarified. 24. Ensue SU design vehicle has adequate room to maneuver at proposed 12' and 14' turnarounds, including without striking screening enclosure at trash tote storage adjacent to 12' turnaround. [Ref. VDOT Road Design Manual, Appendix B 1, Fig. 2-2] Enclosure revised, this is achieved. 25. Provide sight distance line to ensure 100' min., unobstructed stopping sight distance through curvilinear section with perpendicular parking, Road A. Per Design Standards manual, this is achieved by having a min. radius of 120' for curvilinear perpendicular parking. This has been achieved, and radius is noted. 26. Label all easement linework. Noted. 27. Label all drainage easements downstream of any SWM facility (incl 38 raingardens) as public drainage easements. Also, reference /address WPO201900053 12/4/19 Engineering review comments. Noted, esmts are public. 28. Provide deed bk.-pg. reference to recorded (off -site) sight -distance easement (right), 390' for 35 MPH, across TMP# 61-190. Ref. Ecovillage Proposed Entrance Layout, SE Engineering, 02-27-2019. This easement is required prior to Final Site Plan approval. There is no safe egress from development unless this sight -distance easement is obtained /recorded. Show /label sight distance easement on C3. Noted, the developer is working on this. We have advised that this is critical, and the entire project approval hinges on this easement. 29. C3/C4: Identify multi -use pedestrian trail material, either in legend, on plan, or both. Provide typ. detail. Noted, a section has been added. 30. C3/C4: Show northern -most extent of 14' Emergency Fire Access (Secondary Exit) point of connection with: Rio Road, Ex. paths /sidewalks, etc. Any work within VDOT R/W Rio Road E, requires land use permit, and VDOT approval. Noted. 31. Note: Road Plan should provide profile of 14' Emergency Fire Access for comparison with fire apparatus ground clearance requirements. Noted. C5 32. With CG-6, ensure no nuisance ponding. Provide spot elevations as needed to ensure positive drainage. Noted. Positive drainage provided. 33. Revise 8% grade < 5% where Road A serves perpendicular parking spaces. (18-4.12.15.c.) Noted, this is achieved. 34. Revise 6% grade < 5% where Road A serves perpendicular HC-parking spaces. (18-4.12.15.c.) Noted, this is achieved. 35. Road Plan approval requires 70' CL radius (20 MPH design speed) 4% super -elevation, but proposed grade reverses required super -elevation, causing inadequate side friction through the 70' R curve. Revise per Exhibit 5, AASHTO Guidelines for Geometric Design of Very Low -Volume Local Roads (ADT < 400). Noted, a 2% superelevation for a 70' CL radius achieves adequate side friction for this radius. See attached calculations. Combined with the added guardrail, this curve is safe for the residential low - volume, low speed use. Calcs attached to this response. 36. Provide inlet capture along inside of Road A revised 70' R curve (w CG-6). Noted, provided. C6 37. Relocate SWM Facility access (MH) from parking space to parking lot access aisle, to permit access. Due to drive aisle width for angled parking, this could not be fully achieved. However, MH access is on the stripe, which leaves room for maintenance access even if there is a car parked there. In reality, the HOA will coordinate BMP maintenance with the residents, and part of this coordination responsibility will be to ensure there is access to the system. While this might not be an ideal situation, we have had similar BMP setups in several other subdivisions without issue. It just take a bit more communication on the ground. 38. With CG-6, revise depiction of VDOT-typ. inlets. Integrate inlets with CG-6 as opposed to cut /fill section. Noted. 39. Label StormTech /Bayfilter SWM Facility Easement width. Compare with ACDSM diagram /equation, p. 15; image, below (Ensure Min. width for proposed SWM Facility — provide calc. /show equation): BMP diam. = 17', depth=5'. Max grade above BMP = 418, BMP Stone invert = 404.5. Esmt width = (17+2+2*(418-404.5-5)+10) = 46' 46' width provided. Dimensions labelled. 40. C6/C7: Revise storm inlet /pipe design consistent with WPO201900053 Engineering review comments. Noted. 41. C8: Relocate plantings to resolve conflicts with proposed SWM Facility or public drainage easements, including 38 individual raingardens (easements not currently shown). As a general rule, do not locate plant center -points within 2' of an easement for storm pipe, or SWM facility, since plants are not points, but develop central stems /trunks, and extensive root systems. Tree protection typically requires canopy to be located outside limits of disturbance. In this case, a better design is to ensure mid- to large -caliper species canopies lie outside public drainage easements. Once SWM facility easements are shown, Engineering anticipates revision to plant locations. At least 3 large shade trees are shown inside raingardens; at least 3 large shade trees touch raingardens. All six, and perhaps others, must be relocated for raingardens to function, or be maintained, or for FSP /WPO plan approval. Noted, street trees are now medium shade trees. Trunks have been moved out of easements, and out of raingardens. However, there is not enough space onsite to place trees such that canopies are outside easements. We have provided a plan that balances zoning requirements (street tree locations) and locations for better maintenance practice. 42. C15/C16: Revise storm sewer profiles consistent with WPO201900053 12/4/19 Engineering review comments. Noted. C16 43. Revise easement across TMP #61-21013 to New 20' Public Drainage Esrnt. An easement downstream of a SWM facility is public. Albemarle requires access for future inspection /possible maintenance. Noted, they are now public. 44. Please check (TMP #61-21013) Parcel A-1-A label; this appears inconsistent with GIS /Real Estate records. Label updated. 45. C17: Provide copy of recorded on -site sight -distance easement, left. Sight -distance easements (left /right) are prerequisite to FSP approval. Noted, this is pending. See response 28, above. The developer has not secured these, yet. 46. Sign /date C1 of FSP. There is instance of recorded Shimp Engineering Site Plan with unsigned /undated C1 PE -seal, marked review only. Albemarle will (try to) avoid this in the future. (Ref. SDP2018- 00039) Noted, all sheets signed and dated. 47. Revise per 18-Sep 2018 Engineering ISP review comment 10, image, below: "Slopes steeper than 3:1 must specify a plant type or grass on the landscape plan that can withstand the steep slope" Noted. Steep slopes groundcover spec provided. 48. Provide geocell paver detail. Detail provided. If you have any questions or concerns about these revisions, please feel free to contact me at keane@shimp-en in�g com or by phone at 434-299-9843. Regards, Keane Rucker, EIT Shimp Engineering, P.C. AASHTO—Guidelines for Geometric Design of Vei)� Low -Volume Local Roads (ADT 5400) Metric Maximum Minimum radius (m), Rmin design side Max. superelevation rate (%), emax Design speed friction factor, (km/h) fmax 4. 6 20 0.350 10 10 30 0.312 20 20 40 0.252 45 40 50 0.214 80 70 60 0.186 125 115 70 0.163 190 175 US Customary Maximum Minimum radius (ft), Rmin design side Max. superelevation rate (%), emax Design speed friction factor, (mph) fmax 4 6 15 0.330 40 40 20 0.300 80 75 25 0.252 145 135 30 0.221 230 215 35 0.197 345 320 40 0.178 490 450 45 0.163 665 605 Exhibit 4. Maximum Side Friction Factor and Minimum Radius for Horizontal Curves on Higher Volume Low -Speed Urban Streets (1) A risk assessment by Neuman (3) found that because established horizontal curve design criteria are based on driver comfort levels, rather than loss of control, the criteria for fm,,x and Rmm can be relaxed for very low -volume local roads with no discernable degradation in safety. The specific criteria applicable to horizontal curve design for new construction projects and for existing very low -volume local roads are presented below. New Construction The following guidelines are recommended for design of horizontal curves in new construction of very low -volume local roads: • For the design of very low -volume local roads without substantial truck and recreational vehicle volumes, acceptable operations can be obtained with smaller curve radii than those shown in Exhibit 3. Design radii based on a reduction in design speed of 10 to 20 km/h, or 5 to 10 mph, may be used. The maximum reduction, in design speed of 20 km//h or 10 mph is generally appropriate for roadways with speeds of 70 km/h [45 mph] or more and with average daily traffic volumes of 250 vehicles per day or 24 Design Guidelines ! less. For roadways with average daily traffic volumes of 250 to 400 vehicles per day without substantial truck volumes, the appropriate maximum reduction in design speed is 15 km/h or 10 mph. • For the design of very low -volume local roads carrying substantial recreational vehicle and truck traffic, design radii based on no reduction in design speed should be used at very low speeds (e.g., 20 km/h or 15 mph). This guideline reflects the greater likelihood of truck rollover at low speeds.,,1t higher speeds, design radii based on a reduction in speed of no more than 10 km/h or 5 mph, may be used. - The specific guidelines for the design of horizontal curves are presented separately for six categories of very low -volume local roads. These are: • rural major access, minor access, and recreational and scenic. roads with average daily traffic volumes of 250 vehicles per day or less • rural major access, minor access, and recreational and scenic roads with average daily traffic volumes from 250 to 400 vehicles per day ■ rural industrial/commercial access, agricultural access, and resource recovery roads • urban major access streets with average daily traffic volumes of 250 vehicles per day or less and urban residential streets • urban major access streets with average daily traffic volumes from 250 to 400 vehicles per day • urban industrial/commercial access streets, ` Horizontal curve design criteria for new construction of roads in each of these six categories are presented below. "••-�� Maier Access. Minor Access, and Recreational and Scenic Roads �o h0�•'zd� c ✓�vCs a cca vr'lr�se R r",'„ = 70 ' A104 (pfi'vrOr- rhrCcf, cl�� i/,�os/Q(qy, Cv/--e I CS q FFrr f:ke n�u,'� p4/k'n1 �o{-� V 2 _Dole 15R = 0,3 3 (exh#h,'L y) R , 70 e 1� 2 �/o SV pere fe�4 f•� n 0,33 = V -0.v2 i s • 70 361,5 = 1,/ 2.