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HomeMy WebLinkAboutSUB201600092 Correspondence 2018-12-20Attached is our review letter for SUB201600092 North Pointe Section 1- Road Plans - 12-6-16, which includes the following comments: 1. Please label streets on the Overall Plan and Grading Plans. Also, please correct the scale on the Overall Plan, Sheet C-2A. Street names have been added to the requested sheets and the scale correct. See sheets C-2A and C-4-C-4C. 2. Most crosswalks near the roundabouts are not angled at the splitter island but continue straight across, however some do not, please explain. The crosswalks have been shown either straight across or angled at the splitter islands to best align with the CG-12 locations. 3. Please remove the pedestrian crossing near the Northfork Drive intersection with Disregarding this incomplete comment per emails from Justin Deel and Adam Moore on 5131118. 4. The pool house entrance on Northfork Drive does not meet corner clearance spacing requirements. An access management spacing exception, in which we would expect an analysis of the entrance and expected queuing, will be required. This entrance has been removed. See sheet C-3C. 5. All Grading Plan Sheets, C-4 to C-4C — (a) Please provide legible labels of horizontal road geometry to the grading plan sheets (e.g. PC's; PT's). Legible horizontal road geometry has been shown on C-4 to C-4C. (b) Please provide legible street names with their respective design speeds. Legible street names and design speeds have been shown on C-4 to C-4C. (c) Please remove all fire hydrant control valves from the street pavement areas; fire hydrant control valves are to be installed behind the curb per the fire hydrant detail on Sheet C-913. The fire hydrant GVs will be installed behind the curb per the standard detail — we cannot show them outside of the pavement without removing them from the plan due to scaling. (d) Label roundabouts. Roundabouts have been labeled on C-4 and C-4C. 6. Grading Plan Sheet, C-4 — (a) guardrail should be specified in fill sections of roadway where finished roadway grades are 6 vertical feet or more higher than the adjacent finish ground grades; this would include much of Crosscreek Drive. Please provide guardrail warrant worksheet(s). Per Table A-2-1 of the VDOT Road Design Manual, the required clear zone (from edge of driving lane) for a roadway that is 40mph or less, over 6000 ADT, and has a 3:1 backslope is 14-16 feet. The plan proposes 15 feet from edge of pavement to the start of the 3:1 slope on Crosscreek Drive therefore guardrail should not be necessary. 7. Grading Plan Sheet, C-4A — Although the cul-de-sac is designated as a temporary turn -around it is at the end of a 700-foot long road that will serve approximately 13 lots for an unspecified period of time. As such it will need to be constructed to standard cul-de-sac criteria, with the exception of installing curb and gutter around the perimeter, as follows: (a) make the cul-de-sac radius 45' OR a 40' radius with No Parking signs specified around the perimeter; (b) reduce the centerline slope of the cul-de-sac from its current 6.5% to 4.0%; (c) label the station of the radius point and edge of pavement at the end of the cul-de-sac; (d) label the radius of the cul- de-sac that is to be utilized; (e) specify a barricade type to be used at the end of the cul-de-sac at the top of the fill section; (f) label the end of the curb and gutter at or near the curb drop inlets and specify how to transition drainage from gutter flow to the roadside ditch. This comment is no longer applicable due to layout changes and removal of the temporary cul- de-sac. 8. Grading Plan Sheet, C-413 — label the cul-de-sac radius on Northfork Court. It appears to be 45'. The cul-de-sac radius has been changed to 48' and labeled on the plan. 9. Drainage Structure Summary Sheet C-4D — (a) verify that RCP Class III pipe is of adequate strength for the deep -install sections of pipe; (b) Per the Drainage Manual and Road and Bridge Standards, Detail 106.14, SL-1, Safety Slabs are required for manhole and drop inlet structures greater than 12 feet in height. This specification with the required number and spacing of the slabs should be listed for each applicable structure. Pipe class has been revised as necessary due to depth — see "material" column of the drainage structure summary. Safety slabs have been specified in the "steps" column of the drainage structure summary. The appropriate VDOT detail has been added to C-14 which can be referred to for number and spacing of slabs. 10. On all Street Profile Sheets - (a) underneath the street name list the design speed and the corresponding minimum allowable Sag and Crest K values; Design speeds, minimum K values, and minimum SSDs have been provided with the street name on each profile. (b) Per the Road Design Manual, Appendix B(1), page 22, a 50' landing at 2% maximum grade is required. Landings have been provided where requested. Additionally, please show stopping sight distance and K values per the design speed at each street intersection and at all vertical curves. As noted above, design speeds, minimum K values, and minimum SSDs have been provided with the street name on each profile. Showing the required stopping sight distance and minimum K values at each intersection and vertical curve would be excessive since the requirements are now noted at the top of each road profile and the design K value corresponding to each vertical curve is provided in the curve labels. Road and Drainage Profile, Sheet C-7 — (a) there appears to be a missing centerline intersection label at about 13+60, please verify that all pipe crossings are shown on the profiles; (b) label Roundabout 2 on the profile from about 19+75 to 21+50 (similar to the horizontal arrow used for the vertical curves); there appears to be a missing pipe label for Pipe #17 on the storm profile. These items have been addressed as requested on the C-7 road profile. 11. Road and Drainage Profile, Sheet C-7A — (a) an intersection landing, per item 6 above, is needed at 30+50. Design has been revised to include the appropriate intersection landing. 12. Road and Drainage Profile, Sheet C-76 — (a) the vertical curve at 25+80 must be redesigned to the appropriate Sag K value; this will likely affect the crest vertical curve at 28+80; (b) label Roundabout #1 as occurring from 23+50 to 25+50. The vertical curves designs have been revised to meet minimum K values and the roundabout labeled as requested. 13. Road and Drainage Profile, Sheet C-7C — (a) label Roundabout #2 as occurring from 41+50 to 44+00; (b) redesign the vertical curve at 43+80 to the appropriate crest K value; (c) label the slope of the tangent (-4.16%) at approximately 33+75. The roundabout has been labeled, the vertical curve design revised, and the tangent slope labeled. 14. Road and Drainage Profile, Sheet C-7D — (a) redesign the vertical curve at 14+40 to the appropriate sag K value; this will likely affect the intersection elevation of NorthFork Drive (b) Show the intersection sight distance at 14+40; (c) the intersection sight distance labeled 19+00 to 23+50 should be corrected to 280'. Vertical curves for this profile have been redesigned appropriately and the intersection sight distances shown/corrected. 15. Road and Drainage Profile, Sheet C-7E — (a) the vertical curves at 28+40 and 29+50 must be redesigned to the appropriate K values; (b) there appears to be an incorrect intersection label at 28+75; (c) label the items listed for the cul-de-sac revisions from comment #3 above, onto the profile and show the slope of 4% or less. Vertical curves for this profile have been redesigned appropriately; the intersection label has been corrected, and the temporary cul-de-sac discussed in comment #7 above has since been removed from the plan. 16. Road and Drainage Profile, Sheet C-7F — (a) adjust the starting elevation at 10+00 as necessary from comment #11 above and design a landing per comment #6 above; (b) there appears to be an incorrect intersection label at 14+25; (c) redesign the vertical curve at 14+75; (d) design an intersection landing for the intersection at 20+75. Starting elevation and landings have been revised per comment #10 and those above, intersection label has been corrected, and vertical curve at 14+75 has been redesigned. 17. Road and Drainage Profile, Sheet C-7G — Label Roundabout #1 as occurring from 16+20 to 18+25. Roundbout has been labeled on the Rocky Creek Drive profile, now located on C-7H. 18. Typical Sections, Sheet C-9C — (a) Show the "decorative wall" on the Cross Creek section, outside of the street right-of-way; (b) Provide alternative typical sections for locations that may require guardrail. The decorative wall has been shown on the typical sections as requested; R/W has been narrowed such that the wall is outside of it. See response to comment #6 regarding guardrail. 19. Please include pavement design worksheets (submitted on separate 8.5 x 11 pages) on Sheet C- 9A. Pavement design worksheets have been added to C-9A as requested. Roundabouts 20. Include the fastest path calculations ('R' values) as recommended in the NCHRP guidelines. We have included a table of the applicable R values on the plan as requested. 21. The approach deflections still do not appear to be acceptable. The 'R' values above should show if these are adequate. Some reverse curves on the approaches may be needed to achieve acceptable deflections. It's my opinion we are properly balanced between the R values being large enough to needed to allow the Natural Path alignment objectives while still maintaining speed control. For 20-25 MPH single lane roundabouts the R values within the roundabout should be between 75 and 175 which the R values we show accomplish. https://safetV.fhwa.dot.gov/intersection/innovative/roundabouts/fhwasa10006/ 22. The auto -turn analyses appear to be adequate. However, it appears that the approaches have been designed based on these analyses. Note that larger vehicles can use the apron if necessary to traverse the roundabout. Agreed. The inscribed radii of the two roundabouts were discussed and agreed to with Chuck Proctor, Nathan Umberger, and Troy Austin on December 1, 2015 in a meeting at the Culpepper district. The Northern Roundabout (120ft inscribed diameter) and the Southern Roundabout (150ft inscribed diameter) are within the FHWA single lane roundabout criteria (90-180ft inscribed diameter). In addition, we have designed multiple roundabouts in the Richmond Market that mirror those proposed at North Pointe. Enlrancc Il�c Clrculalery roadway Cerrtral Island Len4scep� brAfar Splltt9r Island 7n Xaproa .' i ri Exll Enay lk c ldle padaslrlan uses kg igure 2: Roundabout Design Features oundabouts have been classified into three basic categories according to size and number of lanes to facilitate discussion of specific performance or design issues: iini-roundabouts, single -lane roundabouts, and multilane roundabouts-1- These are summarized in Table 1. Tahlo '1• Anrsn�lvhn:rtf aYnnnry !'mm�a�ienn Design Element Mini Roundabout Single -Lane Roundabout Multi -Lane Roundabout Desirable maximum entry 15 to 20 mph 20 to 25 mph 25 to 30 mph design speed (25 to 30 kmm) j (30 to 40 kri (40 to 50 kmlh) Maximum number of entering 1 1 2+ lanes per approach Typical Inscribed circle diameter 45 to 90 ft 90 to 180 ft 150 to 300 ft (13 to 27 m) (27 to 55 m) (46 to 91 m) Central island treatment Fully traversable Raised (may have traversable Raised (may have apron) traversable apron) Typical daily service volumes on Up to approximately Up to approximately Up to approximately 45.000 4-leg roundabout below which 15,000 vehlday 25,000 vehlday vehlday for two-1 may be expected to operate roundabout without requiring a detailed capacity analysis (vehlday)` 'Operational analysis needed to verify upper limitfor speck applications. 23. It is also recommended and that the last 20 feet of the approach be a tangent section that aligns with the receive path so the vehicle is pointed toward the lane not the apron. We agree and have had our fastest path geometry reflect this tangent section. 1 believe where your comment is also meant the request opening up the acute angle radius within the roundabouts to allow the entry vehicle the ability to align more easily with the receiving path so we have modified the previously shown roundabouts to accomplish that per the markup below: Figure 7: Fastest Vehicle Path Through a Single -Lane Roundabout I �I I111 'I I f 5�+ �i Northern Roundabout — red shows modifications: 24. Consider offsetting the entries to the left slightly to provide room for the deflection. Note that the exit lane does not need much deflection, similar to a pinwheel. We have modified the entry islands slightly to the left to provide for the additional deflection room. 25. Roundabouts that are on a grade (tilted plane) will require special drainage design to insure the water drains properly away from the apron and does not freeze during the winter weather conditions. Please consider revising the roundabouts so their profiles are on plane (i.e. a landing at each entry). While we also like roundabouts that are center crowned we must have both of these roundabouts on what 1 term modified tilted planes. For example, on the southern roundabout the main road through (Northpointe Boulevard) will remain in a crown section but Crosscreek Drive will have to be a tilted plane as we are coming up grade wise across a FEMA floodplain crossing and exploration with a track hoe has determined that rock is underlying the area (approx. 8-10 feet in depth). So Crosscreek Drive must continue to rise in elevation across the roundabout as that roadway continues uphill. Furthermore, on the northern roundabout once again the main road through (Northpointe Boulevard) will remain in a crown section but Lewis and Clarke Drive is dropping in elevation towards a major stream/creek crossing and such it must continue to fall in elevation towards that natural low so that the fill is minimized in the wetlands crossing that will occur at this location. 1 should point out that we have included multiple flanking storm drop inlets to assure that drainage and cross slopes can be achieved.