The URL can be used to link to this page

Home My WebLink AboutWPO201800016 Study 2020-10-15TIMMONS GROUP YOUR VISION ACHIEVED THROUGH OURS. October 15, 2020 Mr. Chris Schooley University of Virginia Foundation 1 Boas Head Pointe Charlottesville, VA 22903 RE: Birdwood Hole 14 Drainage Analysis Dear Mr. Schooley: 608 Preston Avenue Suite 200 Charlottesville, VA 22902 P 434.295.5624 F 434.295.8317 www.timmons.com The University of Virginia Foundation has requested that Timmons Group analyze the drainage area, associated with Hole 14, that drains to TMP 076CO-00-OA-01800. Per our site visit on Tuesday, September 15'", with both the County and the adjacent home -owner, we discussed evaluating the current conditions against pre -developed conditions to aid in the reduction of flow to the parcel noted above, in particular concentrated flow. During the site visit we discussed berms and diversions around the area, as well as the sediment basin, that was left in place. Originally, these measures were coordinated with the homeowners and thought to be to the benefit of the downstream property, however the concentration of flow has created adverse impacts that we are looking to mitigate. Timmons Group revisited the property Tuesday, September 22ntl, walking the site to evaluate the post - development conditions of the graded golf course against what was originally there regarding grading patterns. After the analysis there are five items to note with three of those requiring action. Image 1 below shows Hole 14, looking south from the approximate midway point of the fairway. The contouring of the slope on the left side of the image is recognizable when compared to the pre -developed topography shown in Image 2, as these areas and grades were honored in the golf course redevelopment. Image 1: Hole 14 looking south with tee boxes in background CIVIL ENGINEERING I ENVIRONMENTAL I SURVEYING I GIS I LANDSCAPE ARCHITECTURE I CONSTRUCTION SERVICES You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Additionally, the pre -developed condition featured a swale that directed water to the south of the previous hole. This is very much in line with what can be observed in the first cut off the fairway in this location currently. Image 2 highlights this on the pre -developed topographic condition. Currently, this swale drains to the left -in -place sediment basin. The sediment basin should be removed, allowing the swale to shift to sheet flow as it reaches the southern portion of Hole 14's fairway. 0 Image 2: Pre -developed drainage swale location During the site visit, it was also observed that there appears to be a slight swale or diversion located to the east of the steepest area to the east of Hole 14. This area is shown in Image 3 below (the Image is looking towards the south). This may have been a clean water diversion for the installation of the recent RWSA waterline that was installed. This diversion should be graded out and removed, reestablishing sheet flow to the east, inline with the pre -developed grading, as it is currently directing additional water towards the south and TMP 076CO-00-OA- 01800. 2 1 P a g e You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Lastly, the area around the tee boxes, as shown in Image 4, is having its drainage directed via a berm towards the sediment basin that is to be removed. This berm, shown as having longer plantings in the image below, should be removed. This removal will allow the tee boxes to drain towards the east in a pattern that is more consistent with pre -developed sheet flow. It was also witnessed during the September 16h meeting that a small ditch line has been installed in close proximity to the private property owner and Birdwood golf course. This ditch also needs to be removed to ensure pre -developed drainage patterns continue. 3 1 P a g e You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) Additionally, in an effort to best mimic the previous site conditions, we have discussed with Albemarle County Engineering to replace the shrub and tree cover that was previously between the golf course and the residential lots. The area is approximately 7,600 square feet and will be replaced in kind. These future plantings should be mindful of the RWSA waterline that was recently installed, as they will need to stay clear of the associated easement. Image 5: Existing vegetation to be replaced. In summary, the following items have been observed, with the items in bold necessary for remediation and improvement (See Image 5): 1) The current shaping of Hole 14 is similar to what it was previously, as made evident by the topographic contouring. M You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) 2) In the predeveloped condition there was a swale that ran alongside east end of what is now Hole 14, directing water to the south. 3) The diversion located to the east of Hole 14 should be removed, allowing stormwater to maintain a drainage pattern towards the east and remain in sheet flow. 4) The sediment basin should be removed, along with all downstream improvements, including riprap. The previous swale lines should be reestablished per pre -development topography. 5) The berm to the east of the tee boxes should be removed, along with the shallow ditch line close to the property line with the adjacent neighbor, allowing for sheet flow from the area. The shallow ditch line should be graded minimally, promoting sheet flow, without denuding more area then necessary. 6) Replant vegetation, shrubs and trees, to mimic what was previously on site within this drainage area. 7) Mowing of brush areas, shown in Image 7, shall be limited to no more than two times per year. Image 6: Remediation and Improvement Plan 5 1 P a . P You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com) i SOIL'TYPE;i o � � J, • ' � r Image 7: Brush areas between golf course and residential lots. If you have any questions or comments, please feel free to reach out to us or the University of Virginia Foundation to further discuss the findings that have been noted and displayed here. Sincerely, Craig Kotarski, PE Principal Cc: Fred Missel 2 You created this PDF from an application that is not licensed to print to novaPDF printer (http://www.novapdf.com)