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Home My WebLink AboutWPO201700058 Certified Engineer's Report WPO VSMP 2018-04-27 PROJECT MANAGEMENT S CIVIL ENGINEERING LAND PLANNING ENGINEERING January 21, 2018 Mr. Frank Pohl, P.E. County Engineer Albemarle County Community Development RE: Sparrow Hill Preserved Slopes Certification Dear Mr. Pohl, The construction plans for the Sparrow Hill project have been developed based on a topographic survey provided by Mapping Resource Group, Inc. The map is at 1"=50' scale with 1' contours. MRG did not provide us with a sealed copy initially, upon my request for such a copy I was informed that the licensed surveyor who produced the drawing is no longer with the company. The branch manager of MRG has provided a signed statement that where specified, as in the case of the survey we are working from, the mapping meets national map standards. I hope this will suffice for the purposes of determining its accuracy. The Albemarle County zoning ordinance, section 30.7.4.b.1 spells out the uses that are by-right in the preserved slopes overlay district. Sub-section (h) of the code states that Any use or structure allowed by right or by special use permit in the underlying district"is allowed provided that "the owner submits new topographic information that is based on more accurate or better technical data demonstrating, to the satisfaction of the county engineer, that the slopes are less than twenty-five(25)percent". The preserved slopes layer has been developed from GIS contours provided by Albemarle County. The contour interval of the GIS topography was 4'at the time the preserved slopes layer was developed.While it is unknown if the County GIS data is mapping grade data at 4' intervals, even if it was It is certain that a 1' contour map meeting national mapping accuracy standards is more accurate. Therefore, I find that our aerial topographic map provided by Mapping Resource Group is more accurate and based on better data than the origins of the preserved slopes layer, satisfying the requirements of 30.7.4.b.1.h of the County Code. I further certify that I reviewed the topographic map against the preserved slopes layer and found area's of the preserved slopes overlay district that were less than 25% based upon the more accurate data and I have subsequently mapped those areas as preserved slopes less than 25% on the plans for Sparrow Hill and developed the engineering plans accordingly. BestRe.:rds, Atif /in Shimp Shimp Engineering, P.C. 1 .1VA MRGJGEO January 22, 2018 Mapping Resource Group, Inc. 2601 Princess Anne St.,Suite 202 Fredericksburg,VA 22401 P: 540.479.3750 RE: Crozet Site,Albemarle County,Virginia F: 540.479.3780 MRG GEO#V16-0107 MRGGEO.com To whom it may concern: Project Area This project consisted of a ± 30 acre site located in Albemarle County. The imagery was utilized for geospatial services at 1" = 50' with 1.0' contours. Project Deliverables • DTM consisting of breaklines and photogrammetric mass points • 2D planimetric detail at 1" = 50' in AutoCAD format • 1.0' contours in AutoCAD format Project Accuracy Final mapping documents delivered pursuant to the Agreement, where applicable, shall comply with the standards of accuracy as stated in the United States National Map Accuracy Standards. A copy of said standards are in included in Attachment A contained herein. Sincerely, Mapping Resource Group, Inc. AlIre iie Thomas G. Lussier Branch Manager tlussier@mrggeo.com Mapping Resource Group, Inc. Roger W. Ray&Assoc., Inc. I Crozet Site ATTACHMENT A NATIONAL MAP ACCURACY STANDARDS With the view to the utmost economy and expedition in producing maps which fulfill not only the broad needs for standard or principal maps, but also the reasonable particular needs of individual agencies, standards of accuracy for published maps are defined as follows: 1. Horizontal accuracy. For maps on publication scales larger than 1:20,000, not more than 10 percent of the points tested shall be in error by more than 1/30 inch, measured on the publication scale; for maps on publication scales of 1:20;000 or smaller, 1/50 inch. These limits of accuracy shall apply in all cases to positions of well-defined points only. "Well defined" points are those that are easily visible or recoverable on the ground, such as the following monuments or markers, such as bench marks, property boundary monuments; intersections of roads, railroads, etc.; corners of large buildings or structures (or center points of small buildings), etc. In general what is "well defined" will also be determined by what is plottable on the scale of the map within 1/100 inch. Thus while the intersection of two road or property lines meeting at right angles, would come within a sensible interpretation, identification of the intersection of such lines meeting at an acute angle would obviously not be practicable within 1/100 inch. Similarly, features not identifiable upon the ground within close limits are not to be considered as test points within the limits quoted, even though their positions may be scaled closely upon the map. This class would include timber lines, soil boundaries, etc. 2. Vertical accuracy,as applied to contour maps on all publication scales, shall be such that not more than 10 percent of the elevations tested shall be in error more than one-half the contour interval. In checking elevations taken from the map, the apparent vertical error may be decreased by assuming a horizontal displacement within the permissible horizontal error for a map of that scale. 3. The accuracy of any map may be tested by comparing the positions of points whose locations or elevations are shown upon it with corresponding positions as determined by surveys of a higher accuracy. Tests shall be made by the producing agency, which shall also determine which of its maps are to be tested,and the extent of such testing. 4. Published maps meeting these accuracy requirements shall note this fact in their legends, as follows: "This map complies with national map accuracy standards". 5. Published maps whose errors exceed those aforestated shall omit from their legends all mention of standard accuracy. 6. When a published map is a considerable enlargement of a map drawing(manuscript) or of a published map, that fact shall be stated in the legend. For example, "This map is an enlargement of a 1:20,000 scale map drawing", or "This map is an enlargement of a 1:24,000 scale published map". 7. To facilitate ready interchange and use of basic information for map construction among all Federal map-making agencies, manuscript maps and published maps,wherever economically feasible and consistent with the uses to which the map is to be put, shall conform to latitude and longitude boundaries, being 15 minutes of latitude and longitude, or 7.5 minutes, or 3 3/4 minutes in size. As Published by the United States Office of Management and Budget Mapping Resource Group, Inc. 2 / 87.8 N 3,907,500 f > x589.7/�_� 0/9/00 ZX SO 594 N 3,907,250 598.3 / /:' / j/ / i��/� /j % / / / '�� \� \\ �\ ��✓.% '/g4 / \ 669.3 870.7 174 x IZ ` 70.9 s71.4\� 670. \ 5670 x 868.4 x669.6\\�\ / N 3,907.000 x6723 z 657.5 x858.3 \ \ \\ \ \� \\ / \ \ 87 33 `\ x� ✓ \ / * / i} �8g04\r�y Ib' 604.4 ll \ 673.4 i /'6 5 2.5 5 /6722 671.6 ', �% / tz� x653.6 N 3,906,750 610.6 ` / i r / / l x 553.6 650.6 61 .3659.7 18.4 x 1.4 ° DE •�R��' %/I// SEONC / j /%'r \ , ( �\ 2818.3 \ : \ C\ \ \ \ \\ \ 659.5 ®B64.5x // / 0 N 3,906,500 NSE 6�� 820.8 \ \ \ / 658.5 \ A \x6576 5 �-x i 839.5 / / x 657.7 681.1 660.5 658 c x \ .9 + 897.9 x x 898.4 63729X660--� x 654.7 \ 658.4 650.5 x N 3,906,250 „sLTHO�e.` Crozet Site 1" = 50' with 1',at- �I Date of Photography:March 17, 2016 VRM job-ber: v16-0107 r�w.earo.w y ue x. owme File names. Crozet.dwg Crozet3d.. dwg ® w"' Mapping Resource Group, Inc. 2601 Princess Anne St, Suite 202 Fredericksburg, VA 22401 540-479-3750 0 n N 00 o O 0 N N o N 0 n 0 o o 0 N- o o www.mrggeo.com o M R G IG E O