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Home My WebLink AboutSUB200700133 Review Comments Road Plan and Comps. 2007-05-01� OF AL ,. vIRGI1`IZP COUNTY OF ALBEMARLE Department of Community Development 401 McIntire Road, Room 227 Charlottesville, Virginia 22902 -4596 Phone (434) 296 -5832 Fax (434) 972 -4126 Project: Rolling Meadows Plan preparer: Dustin Greene, DDR [fax 979 -1681] Owner or rep.: Victor Pascarella [PO Box 400 Ivy, VA 22945] Plan received date: 10 Apr 2007 Date of comments: 1 May 2007 Reviewer: Jonathan Sharp A. Road and drainage plans (SUB200700133) 1. Please provide pavement computations. 2. Please provide Albemarle County general construction notes on the plans, verbatim. [DSM CD -19] 3. Please provide the location of street signs on the plans. [14 -423] 4. Shoulders should maintain a slope of 1 ":1' or flatter. [DSM908] 5. Rural intersections should provide a 20' continuance of grade at -2 %. [DSM908] 6. Please provide ditch computations. [DSM909.1A] 7. Please specify end sections and scour protection on the plans. [DSM909] 8. It appears that the culvert may be undersized. The drainage area going to the culvert may be greater than shown. The headwater must be 1.5 feet below the shoulder for the 10 year storm and below the roadway for the 25 year storm. Engineering recommends using RCP instead of CMP. 9. Please show that the 18 inch pipe running across Rte 250 will remain adequate. 10. A road bond amount will be computed once the plans are approved. B. Stormwater Management Plan (WP0200700020) 1. Engineering recommends platting 50 feet of additional stream buffer along the tributary of Stockton Creek to provide water quality for Lots 2 -4 of the site. Plantings should be provided in non - wooded areas of additional platted stream buffer. This will achieve the needed 30% removal rate in this area making BMPs 2 and 3 will no longer be necessary. If done, Engineering will exempt stormwater detention for Lots 2 -4 per Section 17 -314G of the County Code. 2. The area draining to BMP1 requires a removal rate of 50 %, and should be sized to 2.5% of the impervious area draining to it. (Removal rate calculations are attached.) Please provide the sizing calculations. Also, detention needs to be provided with BMP1. Please provide detention calculations. Attached is a detail for combined biofilters and detention structures. This can be found on the web at: httD:// www.albemarle.orL-/uDload/imaL-es /forms center /departments /communitv developm ent/forms /design standards manual/ACDSM Engineerina biofilter basin.ipg 3. The inspection and maintenance access roads cannot be located on critical slopes. The maximum slope of a grass access road is 10 %. Slopes exceeding 10% must be gravel. Access roads cannot exceed a slope of 20 %. [DSM909.2A, 503.1D] 4. The biofilter should specify schedule 40 pvc or equivalent and provide cleanouts for the underdrains. [DSM503.1F] Engineering Review Comments Page 2 of 5 5. The biofilter mix should specify "Luck Bio- Filter Mix or an approved equivalent." [DSM503.1F] 6. The following note should be added to the plans in regards to the installation of biofilters: "Contractor shall contact the water resources inspector 24 hours prior to backfilling the biofilter and request an inspection and approval of the underdrain and the soil mix." [DSM503.1F] 7. Please provide dimensions of the bottom length and width of biofilters on the plans to help ensure proper installation. 8. The scale is incorrect on Sheet 4 of the stormwater plans. 9. The drainage area running to BMP1 is incorrect. 10. Please show easements located around all stormwater facilities. [DSM909.2B(2), 503.1 0,1101 ] 11. A stormwater bond will be computed once the plans have been approved. C. Erosion Control Plan (WPO200700020) 1. Check dams are not adequate sediment trapping measures, as they are only to be used for velocity control. A sediment trap may be necessary on the uphill side of the road entrance to capture runoff. The culvert inlet protection on the downhill side of the road entrance may be adequate depending on the drainage area running to the culvert. Please provide the drainage area going to the existing culvert. [VESCH 3.08, 3.13, 3.20] 2. The check dam details do not match the plans. The details show a 3' ditch depth, where as the ditches shown as not 3' deep. Also, the maximum spacing of check dams should be such that the toe of the upstream check dam is the same elevation of the top of the downstream dam. [VESCH 3.20] 3. The limits of clearing /grading extend into critical slopes. 4. Please provide copies of the construction easements for TMP 56 -105 and 56 -104. Please show the easement locations on the E &S plans. 5. Elevation 650 is incorrectly labeled as 660. 6. Please coordinate all of the plans to reflect the same elevations and benchmark. 7. Please provide a detail of a paved construction entrance, not a gravel construction entrance. Attached is a copy of this detail from the Design Standards Manual. 8. Please provide details of culvert inlet protection and outlet protection. 9. Please specify more clearly the types of seeding to be used for temporary and permanment stabilization. [VESCH ch 6 pgs 13 -14] 10. Please provide existing vegetation and existing drainage patterns. [VESCH ch 6 pgs 13- 14] 11. Please describe stormwater runoff considerations in the narrative. [VESCH ch 6 pgs 13- 14] 12. Please provide the apron length and width for the outlet protection. Please specify the minimum diameter riprap necessary. [VESCH 3.18] 13. Please show that MS -19 is met for runoff draining downstream of the entrance. 14. An E &S bond will be computed once the plans are approved. If you have any questions, please contact me at my email jshaM @albemarle.org, or by phone (434) 296 -5832 ext. 3025. ilx 910-FILTER M IX OR TESTEDAN❑ APPROVED EQUIVALENT V -0" {MINT if{ OUTLET PROTECTION J � � PROTECTION �.I . L ti I I I VNDERDRAIN GRAVEL (AASHTO x+143, CLl:AN�UT W/WATERTIGHT CAP MP) 4"-6" PERFORATED SCHEDULE 44 PVC PIPE OR EQUIVALENT @ 1% 5LOPE (MIN) TO DI OR STORM DRAIN PROVIDE ACROSS ENTIRE WIDTH @ 26 ft O.C. CROSS SECTION Engineering Review Comments Page 3 of 5 TRASH RACK 2' FREE BOARD OR 1' W /EMERGENCY SPILLWAY 4 " -6" NON- PERFORATED PVC PIPE @ 1% SLOPE (P41N) 4" DEEP PEAGRAVEL FILTER LAYER NOTES: 1. THE NEED FOR ADDITIONAL PERMANENT EROSION PROTECTION FROM EDGE OF PAVEMENTTO BOTTOM OF BIORETENTON AREA MUST HE EVALUATED ON AN INDIVIDUAL PROJECT BASIS. Z, PROVIDE 1' -D" PONDING DEPTH TO THE CREST OF AN OVERFLOW STRUCTURE. 3, THE DISTANCE BETWEEN CLEAN -OUTS WILL NOT EXCEED 50 FEET, BIO- FILTER COMBINED WITH DETENTION BASIN NO SCALE Engineering Review Comments Page 4 of 5 STONE 70' MIN- _ CON STRUC -IO N ACCESS 3" SM -2A ASPHALT COURSE 2% EXI5T1 ING PAVEMENT _IF>" MIN, 21A AQQRLFGAIE HAS= PROI ILL STQNF MIN - CONSTRUC -IO'l ASPHALT PAVED ACCESS WA'4 -RACK F_ 2% PAVEMENT FEASTING DRAINIAGE _ TO TO SEaIG "MUST EXTEND =•JL- WIDTH � TRAPPING DEVICE D OF INGRESS AND EGRESS OPERATION PLAN - 12 Y ` POSITIVE DRAINAGE TO SEDIMENT TRAPPING DEVICE FILTER CLOTH SECTION A —A UOL A MINIMUM WATER TAP OF 2" IS REQUIRED WITH A IMINIMUM WASH HOSE DIA. OF 1.5" PAVED WASH H RACK W III pc ¢a�.['"1rx awrr vi v •ax w t'+k . f,t vac rm uw grx.�rs i �ff.wee M i4i Engineering Review Comments Page 5 of 5 Rolling Meadows BMP removal requirements DA #1 13 acres Ipre. 0% Roadway: 780 ft * 8 ft Structures: 2000 sq ft * 3 Driveways: 350 ft * 10 ft Total: 0.36 acres Ipost: 2.7% Removal Rate: 30% DA #2 3.5 acres Ipre. 0% Roadway: 780 ft * 8 ft Structures: 2000 sq ft * 1 Driveways: 100 ft * 10 ft Total: 0.21 acres Ipost: 6.1% Removal Rate: 50% Rolling Meadows DA #1 drainage area; A = 12.9 acres impervious area fraction before; Ipre = 0.00 (min. 20% in develpment area) impervious area fraction after; Ipost = 0.027 water quality volume; A *Ipost *(0.5/12) *(43560/27) _ _23.41 cy pollutant concentration; C = 0.35 (0.35 resevoir cashed, 0.4 rural, 0.7 dev area) pollutant export before; Lpre = 8.77 *(0.05 +0.9 *Ipre) *C *A pollutant export after; Lpost = 8.77 *(0.05 +0.9 *Ipost) *C *A f = 1.0 (see DM p. 5 -39; for dev area where Ipre > 20% use 0.9) REMOVAL REQUIREMENT; (Lpost -f *Lpre) *100 /Lpost = _32.7 Rolling Meadows DA #2 drainage area; A = 3.5 acres impervious area fraction before; Ipre = 0.00 (min. 20% in develpment area) impervious area fraction after; Ipost = 0.061 water quality volume; A *Ipost *(0.5/12) *(43560/27) _ _14.35 cy pollutant concentration; C = 0.35 (0.35 resevoir cashed, 0.4 rural, 0.7 dev area) pollutant export before; Lpre = 8.77 *(0.05 +0.9 *Ipre) *C *A pollutant export after; Lpost = 8.77 *(0.05 +0.9 *Ipost) *C *A f = 1.0 (see DM p. 5 -39; for dev area where Ipre > 20% use 0.9) REMOVAL REQUIREMENT; (Lpost -f *Lpre) *100 /Lpost = _52.3