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Home My WebLink AboutSDP200500022 Correspondence 2013-10-30 PHONE(434)977-0205 - - FAX(434)296-5220 ;o; FAX iN ROUDABUSH, GALE & ASSOC., INC. LAND SURVEYING A PRO FESSIONALCORPORATION ENGPIEERIN 914 MONTICELLO ROAD CHARLOTTESVILLE,VIRGINIA 22902 LAND PLANNING WILLIAM S.ROUDABUSH.L.S. J.THOMAS GALE.L.S. MARILYNN R.GALE,LS. WILLIAM J.LEDBETTER.LS EDWARD D.CAMPBELL III.L.S. Attention: County Engineer,Albemarle County Re: Avon Park,Arden Drive at Route 742 Mr. Brooks, This letter has been written to summarize the as-built conditions at the intersection of Arden Drive and Avon Street Extended (Route 742). In particular,the approved entrance was located at a super- elevated location along an existing portion of Avon Street that exceeded 4%. Although the road is barely in a curve,the existing field data indicates that the slopes across the road range from 7%to 9%. In addition,while heading south the existing road is on a 5%downgrade, and a typical right- turn lane was installed including a small roadside ditch and two inlets utilized to capture all run-off along the widening. From field data and site inspection during average rainfall events,the post development drainage associated with Avon Park does not significantly increase drainage to or across existing Avon Street. As indicated on the attached computations, storm-water from both the 10 year and 100 year storm is fully captured utilizing the existing as-built drainage areas, inlets,and throat lengths, as constructed. An inspection during an average rainfall indicated that water from the existing road surface has always concentrated across the super-elevated roadway, and was not exacerbated by the installation of Arden Drive or Avon Park. It should be noted that the drainage areas, inlet length and inlet depression for each inlet was field verified; for the most part,inlet depression was not discernable, and the inlets were computed assuming there is none present. It should also be noted that the depth of water for full capture by these inlets remained less than the curb height. Accordingly,the inlets are in a weir flow condition, and the inlet depression or lack there-of, does not alter the inlets potential capacity. Sincerely, 14z._c Chris Mulligan, P.E.