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Home My WebLink AboutZMA202000011 Study 2021-01-04608 Preston Avenue P 434.295.5624 Suite 200 F 434.295.1800 T I M M O N S GROUP Charlottesville, VA 22903 www.timmons.com January 4, 2021 Frank Pohl, County Engineer County of Albemarle Dept. of Community Development 401 McIntire Rd Charlottesville, VA 22902 RE: ZMA 2024340-011 Premier Circle Preliminary Pavement Investigation Dear Mr. Pohl, Timmons Group has performed a preliminary investigation of Premier Circle on the existing pavement, including visual inspections, as well as asphalt corings. Calculations, using the VDOT Pavement Design Guide have been prepared and attached to this letter with a recommended pavement section that is acceptable for the proposed use. In addition to pavement thickness and sizing, we also reviewed Premier Circle's geometry, noting variations from VDOT design standards that may preclude its future acceptance into the VDOT system. VISUAL INSPECTION During a visual inspection of Premier Circle it was noted that pavement was cracking, but in general was still safe, functional, and navigable. Striping and signage was faded or non-existent (there was no stop sign located at the southern connection), presenting some safety concerns at both the signalized and non -signalized intersections. Additionally, there was vegetation encroaching into the through lanes that is in need of trimming. PAVEMENT CORING To determine the existing pavement section Timmons Group has conducted a Pavement Exploration consisting of three asphalt cores along Premier Circle. The results of the pavement section cores are included in the table below. A Core Location Plan has been attached as well. ENGINEERING I DESIGN I TECHNOLOGY Measured Pavement Section Thicknesses Asphalt Pavement Base Stone Total Section Core Thickness Thickness Thickness inches (inches) (inches) C-01 4.5 3.0 7.5 C-02 3.0 6.0 9.0 C-03 1 2.5 1 5.5 8.0 The current schedule did not allow for a full geotechnical investigation to field determine the soil's CBR which would be required before construction of a new road. The Pavement Design Guide list CBR values for Albemarle County in Appendix 1. These values are typically very conservative and need to be verified during construction by on -site testing. Due to this, Timmons Group used CBR results from a nearby site for this preliminary analysis (CBR = 18.9). Any final evaluations or design of the pavements section will require a field run CBR test. For the existing condition, as shown in the attached pages from the Pavement Design Guide, the average thickness index provided (Dp) value of 10.3 is less than the thickness index required (Dr) value of 13.3. It is assumed that the average annual daily traffic under the existing conditions is around 960 trips per day, while the thickness of the average pavement supports slightly less then 500 trips per day. It should be noted that this does not mean the pavement will fail, but that resurfacing may be necessary sooner. For the proposed condition, including the housing and commercial space, as shown in the attached pages from the Pavement Design Guide the average thickness index provided (Dp) value would need to be at least 13.9 to equal the thickness index required (Dr) value. If this road was being developed under today's standards it would require 4.5" of asphalt over 8" of stone. Under the proposed condition the trips per day value goes up to 1,120 or just over 18%. Again, this does not result in immediate pavement failure, but the maintenance needs will most likely accelerate. VARIATION FROM CURRENT VDOT STANDARDS Given that Premier Circle was constructed as a private road over thirty years ago, there are inevitably design elements that do not comply with today's VDOT standards for a public road. This is largely due to VDOT's standards being based on a minimum design speed of 25 MPH. While Premier Circle is not currently signed with a speed limit it appears to operate similarly to a private access road in a shopping center which would assume much lower speeds. Should Premier Circle be evaluated for public acceptance at a future date at a higher speed, it is likely that VDOT would expect the following to brought up to current standards: • Sight Distance is not met for the southern entrance of the Royal Inn, as only 130-150' is available, while 280' is required for a 25 mph road. Site distance is not met for Royal Inn at its northern entrance either, as it only has around 210' looking south. In both cases the only solution would be to move the building. • Sight distance issues also existing for Marks & Harrison's office and the Classic Furniture building. Site distance could be achieved, however it would require approximately 20 parking spaces to be removed. • Clear Zone requirements may not be met for VDOT required minimum design speeds. • Entrance spacing to meet Corner Clearance on a Minor Side Street is not met in several instances, with the minimum requirement being 225'. The Waffle House is approximately 60' from the signalized intersection, while the Royal Inn's entrance is approximately 110' from the unsignalized entrance. • Entrance spacing on local roads (50') is not met at the Marks & Harrison entrance and the southern Classic Furniture entrance. • VDOT would require all asphalt, curb, storm infrastructure to be in "like new" condition. In this location, most of the infrastructure is 30-35 years old. • Some of the existing inlet configurations don't comply with current VDOT standards, which would require additional inlets to be added, flanking inlets in a sump. • Curb and gutter do not extend along the entire length of both sides of the road. Adding curb and gutter would also change the drainage patterns and require additional stormwater inlets. While a full evaluation of these items in coordination with VDOT would be required to determine if this road could be accepted by VDOT we believe it is unlikely that VDOT would accept this road. CONCLUSION While there is visible pavement cracking, it does not appear to be creating any safety concerns, however new striping, signage, and general landscape maintenance should be addressed as soon as possible. Furthermore, while a private road maintenance agreement is in place, it is suggested that it should be improved upon and managed with the input of current ownership of all parcels. If you have any questions or comments, please feel free to give us a call at 434.295.5624. Sincerely, � 4 zza*,2, Craig Kotarski, PE Jonathan Showalter, PE Principal Project Manager VDOT — Pavement Design Guide for Subdivision and Secondary Roads in Virginia (revised 2018) Appendix IV Flexible Pavement Design Worksheet for New Subdivision Streets This sheet is intended for use and submission in conjunction with VDOT's Secondary Street Acceptance Requirements County Date: Subdivision Street Name Design Engineer Phone: AADT Projected traffic for the street segment considered, as defined in the Subdivision Street Requirements. CBRD Design CBR = Average of CBRT x 2/3 and modified only as discussed in the Pavement Design Guide. CBRT CBR value of the subgrade sample, taken and tested as specified in the Pavement Design Guide DME VDOT District Materials Engineer EPT Equivalent projected traffic HCV Number of Heavy Commercial Vehicles (e.g. trucks, buses, etc., with 2 or more axles and 6 or more tires). %HCV Percentage of the total traffic volume composed of Heavy Commercial Vehicles. RF Resiliency Factor = Relative value of the subgrade soil's ability to withstand repeated loading. SSV Soil support value of subgrade (SSV =CBRD x RF) Dr Thickness index of proposed pavement design computed by the Conventional Pavement Design Method DR Thickness index required, based on Design AADT and SSV, determined by Appendix II. Step 1: Determine Design AADT Step 2: Determine Design Values CBR, RF, and SSV AADT Sample No. CBRT Resiliency Factor RF %HCV = 100 ( HCV / AADT) or EPT = 20 x HCV Note: For %HCV <_ 5%, use AADT 1 Source Value 2 Table 1 Note: For %HCV>5% , EP->AADT 3 Appendix I DME a roved RF For preliminarydesigns, use the lowest RF value in the equation CBRD x RF = SSV (� x L� Design AADT Use greater of AADT or EPT Step 3: Pavement Design (Check appropriate box and show proposed pavement design below.) ❑ (A) Limited to Design AADT 5 400 - Show pavement material notations and thickness from Appendix IV Tables A and B. -------------------------------------------------------------------------------------------------------------------------------- ❑ (B) Show pavement section as developed in the Pavement Design Guide. Dn = (See Appendix m for material notations and thickness equivalency values (a)). from Appendix II Description of Proposed Pavement Section Material Notation Thickness, h a (a x h) Surface Base Subbase DP must equal or exceed the value of DR. DP = F (a x h) _ 28 30 1 13 12 11 10 9 8 7 6 4 1 VDOT — Pavement Design Guide for Subdivision and Secondary Roads in Virginia (revised 2018) 30,000 Example 20,000 DR = 10.7 (interpolated) 10,000 or more for design parameters 6, 000 SSV 11 and Design AADT = 480 4, 00.0 (intemolated) 3, 000 2,000 SSV Scale 00 ......... . 800 .............. ...... 40600 300 200 100 50 Design AADT Scale 25.0 24.0 23.0 20.0 19.0 18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 MOM 9.0 8.0 7.0 6.4 Minimum 6.0 DR Thickness Index Please refer to Appendices 11 and V for the application of this diagram in the design of pavement. 32 VDOT — Pavement Design Guide for Subdivision and Secondary Roads in Virginia (revised 2018) Appendix IV Flexible Pavement Design Worksheet for New Subdivision Streets This sheet is intended for use and submission in conjunction with VDOT's Secondary Street Acceptance Requirements County Date: Subdivision Street Name Design Engineer Phone: AADT Projected traffic for the street segment considered, as defined in the Subdivision Street Requirements. CBRD Design CBR = Average of CBRT x 2/3 and modified only as discussed in the Pavement Design Guide. CBRT CBR value of the subgrade sample, taken and tested as specified in the Pavement Design Guide DME VDOT District Materials Engineer EPT Equivalent projected traffic HCV Number of Heavy Commercial Vehicles (e.g. trucks, buses, etc., with 2 or more axles and 6 or more tires). %HCV Percentage of the total traffic volume composed of Heavy Commercial Vehicles. RF Resiliency Factor = Relative value of the subgrade soil's ability to withstand repeated loading. SSV Soil support value of subgrade (SSV =CBRD x RF) Dr Thickness index of proposed pavement design computed by the Conventional Pavement Design Method DR Thickness index required, based on Design AADT and SSV, determined by Appendix II. Step 1: Determine Design AADT Step 2: Determine Design Values CBR, RF, and SSV AADT Sample No. CBRT Resiliency Factor RF %HCV = 100 ( HCV / AADT) or EPT = 20 x HCV Note: For %HCV <_ 5%, use AADT 1 Source Value 2 Table 1 Note: For %HCV>5% , EP->AADT 3 Appendix I DME a roved RF For preliminarydesigns, use the lowest RF value in the equation CBRD x RF = SSV (� x L� Design AADT Use greater of AADT or EPT Step 3: Pavement Design (Check appropriate box and show proposed pavement design below.) ❑ (A) Limited to Design AADT 5 400 - Show pavement material notations and thickness from Appendix IV Tables A and B. -------------------------------------------------------------------------------------------------------------------------------- ❑ (B) Show pavement section as developed in the Pavement Design Guide. Dn = (See Appendix m for material notations and thickness equivalency values (a)). from Appendix II Description of Proposed Pavement Section Material Notation Thickness, h a (a x h) Surface Base Subbase DP must equal or exceed the value of DR. DP = F (a x h) _ 28 30 1 13 12 11 10 9 8 7 6 4 1 VDOT — Pavement Design Guide for Subdivision and Secondary Roads in Virginia (revised 2018) 30,000 Example 20,000 DR = 10.7 (interpolated) 10,000 or more for design parameters 6, 000 SSV 11 and Design AADT = 480 4, 00.0 (intemolated) 3, 000 2,000 SSV Scale 00 ......... . 800 .............. ...... 40600 300 200 100 50 Design AADT Scale 25.0 24.0 23.0 20.0 19.0 18.0 17.0 16.0 15.0 14.0 13.0 12.0 11.0 MOM 9.0 8.0 7.0 6.4 Minimum 6.0 DR Thickness Index Please refer to Appendices 11 and V for the application of this diagram in the design of pavement. 32