The URL can be used to link to this page

Home My WebLink AboutWPO201200091 Review Comments Stormwater Management Plan 2012-11-30i" ,. `IRGINZP 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: Plan preparer: Owner or rep.: Plan received date: Date of comments: Reviewer: Keswick Club LLC Golf Course Townes Site Engineering Keswick Club LLC 20 November 2012 30 November 2012 Max Greene WP0201200091 [fax 804 - 748 -25901 [fax 804 - 643 -4208] The Water Protection Plans (WP0201200091) submitted 20 November 2012 have received Engineering Review and do not appear to meet Albemarle County minimum checklist items for approval. Please adequately address the following comments for final approval: A) Variance Request 1) The request to use Modified mud Traps (Wire- supported silt fence with stone weirs outlet installed at the low points along the silt fence) can be approved with the following adjustments to the plans and these notes added to the plan: a) Modified mud traps shall not have a drainage area in excess of 3 acres during any part of the construction process. b) Drainage areas over 1 acre shall have a wet storage pit excavated in front of the stone weir outlet equal to the requirements for temporary sediment traps (Std. & Spec. 3.13) (i.e. 67 cubic yards of storage per drainage acre, not to exceed 4' in depth, with side slopes not to exceed 2:1) C) Modified traps shall not be used in areas where rock or some other hard surface prevents the full and uniform depth anchoring of the barrier. d) An effort shall be made to locate the barrier at least 5 to 7 feet beyond the base of slopes with grades greater than 7%. e) Wire fence reinforcement for silt fence shall be a minimum of 14 gauge and shall have a maximum mesh spacing of 6 inches. f) The wire shall extend a minimum 4 inches into the ground and must be fastened securely to the upslope side of the posts using heavy duty wire staples at least one inch long, tie wires or hog rings. g) If wooden stakes are utilized for modified mud trap construction, they must have a minimum diameter of 3 inches when oak is used and 5 inches when pine is used. Wooden stakes must have a minimum length of 5 feet. h) If steel posts (standard "U" or "T" section) are utilized for the modified mud trap construction, they must have a minimum weight of 1.33 pounds per linear foot and shall have a minimum length of 5 feet. i) Support posts or stakes for this type of application shall be placed a Maximum 10- feet apart (see Plate 3.05 -1) except within the wet storage area. The wet storage area Engineering Review Comments Page 2 of 3 shall have the posts or stakes placed a Maximum 3 -feet apart for added support. j) Silt fence shall conform to the construction specifications for "extra strength" found in table 3.05 -B and shall be cut from a continuous roll to avoid joints. k) The fabric shall be entrenched a minimum 8" in depth and back filled with clean soil. The soil shall be compacted to 95 % over the filter fabric. 1) The height of the silt fence shall be a minimum of 34 inches above the original ground and shall not exceed 48 inches above ground elevation. m) The outlet for the modified mud trap shall consist of a stone section of the wire — supported silt fence located at the low point or point of concentration for storm flows. For drainage areas less than one acres, the measure shall consist of wire - supported silt fence installed as a continuous structure with class Al stone carefully placed on either side of the fence for outlet stability, no filter stone required. For drainage areas from 1 to 3 acres, the measure shall consist of the wire - supported silt fence installed with an opening from 4 to 8 feet wide located in the low point or point of concentration for storm flows. The opening shall have a combination of course aggregate and riprap installed to provide for filtering /detention as well as outlet stability. The smaller stone shall be VDOT #3, #357 or #5 Course Aggregate (smaller stone sizes will enhance filter efficiency) and riprap shall be "Class I." Filter cloth which meets the physical requirements noted in Std. & Spec. 3.19, RIPRAP shall be placed at the stone -soil interface to act as a "Separator." The crest of the stone outlet must be at least 1.0 foot below the top of the Wire - supported silt fence to ensure that the flow will travel over the stone and not over the fence. The outlet shall be configured as noted in Plate 3.13 -2. n) Maintenance: (a) Silt fence shall be inspected immediately after each rainfall and at least daily during prolonged rainfall. Any required repairs shall be made immediately. (b) Close attention shall be paid to the repair of damaged silt fence resulting from end runs and undercutting. (c) Should the fabric on a silt fence decompose or become ineffective prior to the end of the expected usable life and the barrier is still necessary, the fabric shall be replaced promptly. (d) Sediment shall be removed and the trap restored to its original dimensions when the sediment has accumulated to one half of the design volume of the wet storage or eminent failure is evident. Sediment removal from the area shall be deposited in a suitable area and in such a manner that it will not erode and cause sedimentation problems. (e) Stone shall be regularly checked to ensure that filtration performance is maintained. Stone choked with sediment shall be removed and cleaned or replaced. (f) The structure shall be checked regularly to ensure that it is structurally sound and has not been damaged by erosion or construction equipment. The height of the stone outlet shall be checked to ensure that its center is at least 1 foot below the top of the fence. (g) Temporary structures shall be removed when they have served their useful Engineering Review Comments Page 3 of 3 purpose, but not before upslope area has been permanently stabilized. B) Stormwater Management and Mitigation Plan 1) Buffer impact does not appear correct. Any changes within the 100 buffer area is an impact. Please show total buffer impact on the plan for review and comparison to mitigation plan. C) Erosion Control Plan 1) Several drainage areas to modified mud traps appear to be larger allowed per the above requirements. Please redesign the E &SC perimeter control structures in accordance with the requirements. 2) Stone weirs will be field located to insure installation at the low points along wire - supported silt fence. 3) Please include the removal and replacement of cart paths on the WPO plans. The path removal and/or replacement will be part of the overall disturbance. Once these comments have been addressed, please submit 2 copies of the revised plans, calculations, and narratives to Current Development Engineering along with the required review fee and transmittal form. Current Development Engineering is available from 2:30 -4 PM on Thursdays to discuss these review comments. Please contact Max Greene at 434 - 296 -5832 ext. 3283 or email mgreene @albemarle.org to schedule an appointment. [17- 204.f] An application for an erosion and sediment control plan that requires modifications, terms, or conditions to be included in order for it to be approved shall be deemed to be withdrawn if the owner fails to submit a revised plan addressing the omitted modifications, terms or conditions within six (6) months after the owner is informed of the omitted information as provided under paragraph (B). Filc: CDDEI _esc,mit,swm,var_MRG_Keswick Club LLC Golf Course.doc