The URL can be used to link to this page

Home My WebLink AboutWPO201300032 Correspondence 2018-07-240 ROUDABUSH, GALE & ASSOCIATES, INC. $ A PROFESSIONAL CORPORATION s p [AND SURVEYING Serving Virginia Since 1956 ENGINEERING LAID PLANNING ENGINEERING DEPARTMENT SURVEY DEPARTMENT 172 SOUTH PANTOPS DRIVE. STE. A 914 MONTICELLO ROAD JIM L.TAGGART, P.E. CHARLOTTESVILLE. VA22911 CHARLOTTESVILLE. VA22902 WILLIAM J. LEDBETTER, L.S. DUN FRANCA. P.E. PHONE (434) 979-9121 PHONE (434) 977-0205 BRIAN D. JAMISON, L.S. DAVID M. ROBINSON. P.E. FAX (434) 979-1681 FAX (434) 296-5220 DAVIDA. JORDAN. L.S. AMMY M. GFORGF, L.A. INFO(a_ROUOABUSH.COM KRISTOPHF.R C. WINTERS, L.S. July 24, 2018 County of Albemarle Department of Community Development ATTN: Paty Saternye 401 McIntire Road Charlottesville, VA 22902 RE: WP0201300032 Amendment Cascadia Blocks 4 - 7 Dear Mr. Anderson, We have reviewed your comments provided on July 7, 2018, and have provided the following responses: 1. Biofilter #2 was approved with WP0201300032 —why remove it? Expense or difficulty are not alone a decisive rationale. RESPONSE: The stormwater management content of the code of development for cascadia states that : Storm water management to include both quantity and quality control (bmp's) will be provided onsite in various locations throughout the Cascadia development. The preservation areas may count towards stormwater quality management for only the dwelling units in block 6 that cannot be effectively diverted to the stormwater management ponds and other structures along route 20. For these residential units in block 6, roof drains and driveways may be allowed to discharge uncontrolled so long as the discharge is dissipated to the satisfaction of the county engineer and does not cause erosion. We are simply trying to show that our proposed plan is better for the overall project than what is currently proposed. 2. Please ref. Attached WP0201300032 excerpt: "so long as the discharge is dissipated to the satisfaction of the County Engineer and does not cause erosion." RESPONSE: The owner is proposing to provide whips on all slopes on the back side of Block 6 so that the rill erosion of the 2:1 slope will be stabilized. We are proposing a french drain system for the lots immediately adjacent to this slope as well. 3. Uncontrolled roof drain discharge by units constructed to -date (block 6) has eroded constructed slopes, especially those without appropriate landscape cover. RESPONSE: See response #2. 0 ROUDABUSH, GALE & ASSOCIATES, INC. $ A PROFESSIONAL CORPORATION 5 p [AND SURVEYING Seming Virginia Since 1956 ENGINF.FRING LAND PLANNING ENGINEERING DEPARTMENT SURVEY DEPARTMENT 172 SOUTH PANTOPS DRIVE. STE. A 914 MONTICELLO ROAD JIM L.TAGGART, P.E. CHARLOTTESVILLE. VA22911 CHARLOTTESVILLE. VA22902 WILLIAM J. LEDBETTER, L.S. DUN FRANCA. P.E. PHONE (434) 979-9121 PHONE (434) 977-0205 BRIAN D. JAMISON, L.S. DAVID M. ROBINSON. P.E. FAX (434) 979-1681 FAX (434) 296-5220 DAVIDA. JORDAN. L.S. AMMY M. GFORC,F., L.A. INFOO ROUDABUSFLCOM KRISTOPHER C. WINTERS, L.S. 4. When we meet Thursday, please prepare to discuss /address: a. Currently eroding slopes, which require repair /remedy. RESPONSE: Whips are going to be planted on the 2:1 slope, in open space areas. b. Albemarle is open to SWM measures that provide equivalent benefit to biofilter #2 —this is not a narrative discussion, but a technical /calculated approach. RESPONSE: The biofilter #2 removes 0.28 pounds per year of phosphorous. The drainage area of biofilter #2 is less than (i watershed) 16% impervious but we need to go above and beyond to show its removal. There is some science to show that providing whips on the 2:1 slope open space will reduce the amount of pounds per year phosphorous more than the biofilter #2. The trading nutrient reductions nonpoint source bmp in the chesapeake bay watershed appendix a gives 0.50 pounds per year of phosphorous for each acre of land conversion going from pasture to forest in the james river basin west of I-95. while we are not applying to become our own nutrient credit bank, adding 0.56 acres of whips essentially converts the grassed area to forest and we would get 0.28 pounds per year of phosphorous removed. c. Slopes are failing, which is strong supporting rationale for collecting driveway and roof runoff from block 6 residential units. RESPONSE: We are proposing French drains for these lots. d. Alternatives should be evaluated against quality /quantity benefits of biofilter #2. Reference approved SWM plan data. RESPONSE: Water Quantity is not at issue here. The post -developed hydrograph is less than the predeveloped for all storm events. e. Albemarle requests RGA obtain updated photos of slopes behind block 6 units, and bring these for discussion 7/12. RESPONSE: At this time construction has not been completed and final stabilization will occur with whip planting. John, I will call and discuss with you. Please let me know if this approach is workable. Best Regards, Dustin Greene 0 ROUDABUSH, GALE & ASSOCIATES, INC. $ A PROFESSIONAL CORPORATION 5 p LAND SURVEYING Serving Virginia Since 1956 FNGINF.FRING LAND PLANNING ENGINEERING DEPARTMENT SURVEY DEPARTMENT 172 SOUTH PANTOPS DRIVE. STE. A 914 MONTICELLO ROAD JIM L.TAGGART, P.E. CHARLOTTESVILLE. VA22911 CHARLOTTESVILLE. VA22902 WILLIAM J. LEDBETTER, L.S. DUN FRANCA. P.E. PHONE (434) 979-9121 PHONE (434) 977-0205 BRIAN D. JAMISON, L.S. DAVID M. ROBINSON. P.E. FAX (434) 979-1681 FAX (434) 296-5220 DAVIDA. JORDAN. L.S. AMMY M. GFORGF, L.A. INFO(a_ROUOABUSH.COM KRISTOPHF.R C. WINTERS, L.S.