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Home My WebLink AboutWPO201700070 Other 2019-01-25 (2)COUNTY OF ALBEMARLE Facilities & Environmental Services Project Management Division 401 McIntire Road, Room 420 Phone (434) 872-4501 Charlottesville, Virginia 22902-4596 Fax (434) 293-0294 24 January 2019 Frank V. Pohl, PE, CFM Community Development Department 401 McIntire Road Charlottesville, VA 22902-4596 Re: Ivy Road Sidewalk Project W PO 201700070 Dear Mr. Pohl: As provided for in 9VAC25-870-57 "Requesting an Exception", the Project Management Division would like to request an exception for Part II B "Technical Criteria for Regulated Land -Disturbing Activities", 9VAC25-870-66 "Water Quantity" for the drainage outfall at the western limit of the sidewalk improvements located at the east corner of Ivy Road/Stillfried Lane intersection. The reasons for the exception are provided below and followed by a detailed summary. • The small amount of increased impervious area (966 sf) and resulting increase in post -development runoff (0.17 cfs for Q1o) will have an insignificant impact on the downstream drainage system. • The construction of the proposed collection, conveyance and detention system will require the closure of Stillfried Lane which is the only means of ingress/egress for residents and emergency responders to the 54 residential units within the Poplar Glenn development. • The construction of the proposed collection, conveyance and detention system will require the closure of Stillfried Lane upon which the University of Virginia is dependent as there only construction access for the delivery of building materials and the structural steel for their new Ivy Mountain Musculoskeletal Center. • Due to the impacts of the proposed collection, conveyance and detention system's construction and permanent easement on University of Virginia's property, they don't support the proposed drainage system improvements and the granting of the necessary easement. • The outfall from the proposed collection, conveyance and detention system must cross drainage divides and connect to an offsite drainage system. Because of capacity issues in that offsite system the proposed collection, conveyance and detention system cost (approx. $200,000) is excessive when compared to the insignificant benefit achieved. As stewards of the public's tax dollars this cost/benefit is very difficult to justify. Existing Conditions The existing drainage patterns and conditions described herein are also shown in the photographs included as Exhibit A in this request. There is an existing shoulder and ditch that conveys runoff along the frontage of the Teague Funeral Home, across their entrance to an existing grate inlet that is partially obstructed with sod and pavement. Water was observed flowing out of the structure via an outlet pipe in a northwest direction toward the opposite side of Ivy Road, however; the release point could not be WPO 201700070 24 January 2019 Page 2 of 3 located. The inlet is undersized for the drainage area and the overflow crosses Stillfried Lane to the existing curb & gutter and continues to flow west along Ivy Road. At the end of the right -turn lane the runoff is released from the gutter to a grassed shoulder and shallow swale located within the right-of-way and between the edge of pavement and a stone wall that extends the length of the University of Virginia (UVA) property. The shoulder has several wheel trenches and depressed areas that hold water, as well as high areas along the edge of pavement that obstruct runoff from sheet flowing to the swale. The swale has not been maintained and over the years has lost some of its shape and drains poorly. The runoff in the swale is eventually collected by a grate covered inlet just east of the Reed Lane -Ivy Road intersection. Post -development Conditions The sidewalk improvements along the portion of Ivy Road draining to the Stillfried Lane -Ivy Road intersection will create new impervious area as well as convert some existing impervious areas to grass. The net increase in impervious area is 966 sq ft and results in a Q10-post runoff increase of 0.17 cfs and a Q2- post runoff increase of 0.07 cfs. Refer to Exhibits B-1, B-2 and B-3 for more information. Since the drainage system downstream of this outfall was considered inadequate, compliance with the VSMP regulations required the detention of any increase in the post -development runoff. Therefore, our consultant (Kimley-Horn & Assocs.) provided new inlets and a pipe system to capture and convey the post - development runoff to an underground detention pipe and then convey it across the drainage divide to the existing storm pipe system on the UVA property. Our consultant's hydrologic & hydraulic analysis revealed that the UVA drainage system was over capacity and would cause water to backup into the proposed drainage system and render any underground detention non-functional. More information was compiled on all the drainage and storm water management systems built by development within the contributing drainage area to the UVA drainage system and additional analysis was conducted by our consultant. Although the revised analysis showed the existing conditions of the UVA drainage system improved, it was still over capacity. Therefore, the only solution to comply with the VSMP regulations was to design a system detaining additional offsite runoff and increase the size of the underground detention system. As an attempt to address UVA's concerns for the impacts to their property, the length of the system was minimized by providing detention in an underground 6 ft x 4 ft box culvert 70 ft in length with 3 junction boxes. Impacts of Compliance The construction of the proposed collection, conveyance and detention system would require the closure of Stillfried Lane to traffic for long periods of time causing significant access issues. Stillfried Lane is the only means of ingress/egress to the 54 residential units within the Poplar Glenn development. During the road closure residents would be unable to get in or out of their development and fire, rescue and emergency services would be unable to respond. Road closure is also a concern for UVA since during their Ivy Mountain Musculoskeletal Center (IMMSKC) project development meetings with the Poplar Glenn residents they assured the residents that Stillfried Lane would remain open during the duration of their project. Stillfried Lane is also the only construction access for UVA's IMMSKC project. They are dependent on this street for deliveries of their building materials and especially for delivery of their structural steel. Closure for the construction of the proposed collection, conveyance and detention system will have significant impact to the timing and logistics of their deliveries and construction coordination. Staff and our consultant have been communicating and working closely with UVA staff to coordinate the the IMMSKC and Ivy Road Sidewalk projects. In earlier discussions the UVA Office of the Architect staff expressed concern for this projects impact to trees they had worked diligently to protect as they developed their plans for the IMMSKC. Various renditions of the drainage and stormwater management facility were presented and discussed with UVA staff as the design progressed. The final design of this WPO 201700070 24 January 2019 Page 3 of 3 infrastructure will require a permanent drainage easement over UVA property that is approximately 115 ft in length and varies 24 ft to 36 ft in width. UVA staff have reviewed the final plans and due to the impacts of the proposed drainage and stormwater management facility construction and permanent easement on UVA's property, they do not support the proposed improvements and are not interested in granting the necessary easement. They do however, support our request for an exception. Lastly, the outfall from the proposed collection, conveyance and detention system must cross drainage divides and connect to the offsite drainage system on the UVA property. Due to the design needed to overcome the complications caused by the capacity issues in that offsite drainage system and achieve VSMP compliance, our proposed system will cost approximately $200,000 (refer to Exhibit C). This cost is excessive when compared to the insignificant benefit achieved. As stewards of the public's tax dollars this cost/benefit is very difficult to justify. Conclusion/Recommendations Based on the justification above we ask that you approve the requested exception with the conditions listed below. • Elimination of the proposed collection, conveyance and detention system shown on the latest plans. • Post -development runoff released from the east corner of the Ivy Road-Stillfried Lane intersection will continue to follow the existing pre -development drainage pattern. • Replace the existing obstructed grate inlet (Ivy Road Sta 119+48R) with a new VDOT DI-2A inlet (or other inlet type) with a custom cast -in -place box to connect the existing drainage pipes. (Note: the latest plans show it to be replaced with new manhole #3-8). • Include the scraping and repair of the existing shoulder along the south side of Ivy Road from Reed Lane to the start of the right -turn lane (Sta 117+75R) in this project or coordinate with the VDOT Resident Office to have it done as part of their maintenance program prior to the construction of this project. Should you have any questions or need additional information, please contact me at (434) 872-4501 ext. 3376 or at jkelsey@albemarle.org . Very truly yours, Jack M. Kelsey, PE Transportation Engineer Enclosures: Exhibit A Exhibits 131, B2 and B3 Exhibit C cc: Blake Abplanalp Runoff from existing shoulder & ditch crossing Teague Funeral Home entrance to an existing grate inlet. Existing grate inlet obstructed by sod and pavement. Gutter from i► M0 Gutter flow from Stillfried Lane (north side) drains to this inlet. Overflow from the grate inlet crosses Stillfried Lane to the existing curb & gutter and continues west on Ivy Road Existing curb & gutter releases to the shoulder & swale that's to convey runoff to an existing grate inlet before Reed Lane. Existing shoulder & swale need to be reshaped to drain the Street properly. Existing shoulder & swale need to be reshaped to drain the m x street properly. Existing shoulder & swale need to be reshaped to drain the street properly. Existing grass shoulder is obstructing sheet flow from the street Shoulder & swale need to be reshaped to drain properly. Existing grass shoulder is obstructing sheet flow from the street. Shoulder & swale need to be reshaped to drain properly. EXHIBIT B-1 \INLEr AREA (AC4 \ 3-1 0.33 3-2 0,40 3-3 1.13 %, 1� W Z Q CO U W 3ff 4-2 b 4-/ we Drainage Areas to the Ivy Road/Stillfried Lane Intersection East Corner Based on the Drainage Area Map and Data from the Ivy Road Sidewalk Hydraulic Design Report December 3, 2018 by Kimley-Horn & Associates, Inc for the County of Albemarle rrr Low Brush & High Grass Existing Right of Way Low Brush & High Grass EXIST. R/W VDOT Project 722A-2 $ 3`250 _ G 56m� High Brush (Century Link)� o B T /FO �^ C at d Stee/d --------- ----------J Coated Steel F - - -- ----- -- ---- -� — — — --�-T-T-r-T-r - --- - DRAINAGE -� 2; A��' i" i" DIVIDE i'r� fir= SAOC( It IT�yi" i i"�" �" �" 1 ACUTi, �. �e i ex imp 182 sf l i i i - - - - - - - i ex Imp 11 sf ex imp 41 sf - - S%4 ------------ . new imp 229sf - - �� .i � ° D ,D � ,D ♦ new imp 543 sf- --t-5' de ne Wall D 15 r F 0 T 9 6 E 100.00 ; \ , _ I new imp 15Usf . new imp 262 sf / Xl = ` �4� ° ' ° _ — a° _ ��.9. �M • — n° (ST% 00, . , — • �- r 15.00 new `imp 16 sf - - -- =± = _ _ _ - F ° ° ° . ° _ �.�i/� ,' 1% -C� �r" • -' r UA r� P m (0. 33 ac) ,oP' VDOT _ - .Y ► 4 .fJ1I }. ..- f0 C. �' q i ONG• 6, X �i 3-5 ��JJJJJt ► _ ''' . TEMP EASE ENTRANCE / + a) ro D1 o' a EWALK ► jI ti ; : D OTHERS 3_7 o Cc ► op 11 1 M. R E k+JE. TR. I1X� F r E PIP & �lVgURE BEG ° - \ . S FRIED L i = ST \ ST ILLFRIED L C SfR. \\ Z o 9 oa \\\\ \� a \\\ o ��Q - \ � ° C \\ i THE RECTOR AND VISITORS OF THE UNIVERSITY OF VIR 1�34 DB 251 PG 005 O ll• 16 AC. \\ PARCEL ID* 06000-00-00-OJIOO \\\ -•' - SPROP. . EASE. FOR 1 �� 11 o 1� UI EASE. (0. 13 a c 0/yS _ PROP. ' F �• T R E' P ' P. PER • DO ll) ) SLOPE 11 1 0 o Z� � M �G? PR P.'J�ERlU �jv, t� ,��` 1', �n 'i1W �', �� i` ENERGY E� - `�R. UT o I k , v u II , fP� OP.- ,„clrle�✓__. 11 III ',zzz DA 3-2 CL I �1� II In � I, O U Q� l ) ` (0.40 ac) �- II 11 Q), (-- o 00 � ' �I II 11� , J I ■ ',';, \� ,• 1 + ck II a �, Q) , `I J \) 2 Story BriII 11� Li11 0 1 III ', ,vi II 1 N J # 2260 °_ Q o U Q � u, -- ideWalk z cz o 0 0 BLUE = NEW IMPERVIOUS AREA �, w �, Cl- RED = EXISTING IMPERVIOUS REMOVED D CO .STI o w � o c T 200.62.50 N m DA # Post-Dev Increased Impervious Area �'� o DA 3-1 543 + 229 - 41 = 731 sf o o o v i o DA 3-2 262 - 182 = 80 sf ° o DA 3-3 150 + 16 - 11 = 155 sf m o ° w co ~ o Net Increase Impervious Area = 966 sf c' o N 00 0 �r� ao U cp -0?.0( �o 6 \ C0 o LLJ QD 002 a ci � � JO EPH . TEAGUE & `' o # # I ARY JANE TEAGUE EXHIBIT B-2 Post -development Drainage Areas with Net Increased Impervious Areas Based on the Ivy Road Sidewalk PS&E Plans dated December 21, 2018 by Kimley Horn & Associates, Inc for the County of Albemarle EXHIBIT B-3 Ivy Road-Stillfried Lane Outfall: Change in Qio-post and Q2-post Computations Refer to Exhibit B-1 Post -development Refer to Exhibit B-2 Notes: DA # Area (acs.) C CA I CA Q10 (cfs) Q2 (cfs) Imp Area Increase (sf) Referenced study 3-1 0.33 0.75 0.244 0.244 731 assumed "B" type 3-2 0.40 0.75 0.302 0.545 80 soils: Cturf = 0.20 3-3 1.13 0.85 0.959 1.504 9.63 7.34 155 CimP = 0.90 Exhibit B-1 and Post -development data above are from the Ivy Road Sidewalk Hydraulic Design Report December 3, 2018 by Kimley-Horn & Associates, Inc prepared for the County of Albemarle Compute Pre -development Accumulated CA Based on Area Changed from Grass to Impervious DA # 3-1: CApost = 0.244 A CA = ( 731 sf / 43560 )(0.9 - 0.2) = 0.0117 CApre = 0.2323 DA # 3-2: CApost = 0.302 A CA = ( 80 sf / 43560 )(0.9 - 0.2) = 0.0013 CApre = 0.3007 DA # 3-3: CApost = 0.959 A CA = ( 155 sf / 43560 )(0.9 - 0.2) = 0.0025 CApre = 0.9565 Y CApre = 1.4895 From the referenced study: Inlet Time = 6.0 mins. Ito = 6.35 12 = 4.9 (IDF Curves -Albemarle County, 7-8-2005) Compute the Difference Between the Q post and Q pre Qio-pre = I CApre (6.35) = 1.4895 (6.35) = 9.458 cfs Qio-post = 9.63 cfs A Qio = 0.17 cfs Q2-pre = Y CApre (4.90) = 1.4895 (4.90) = 7.299 cfs Qio-post = 7.34 cfs A Q2 = 0.07 cfs i0:V:u:3111r0 PROPOSED COLLECTION, CONVEYANCE AND DETENTION SYSTEM COST ESTIMATE 15" CONC. PIPE LF 114 $ 75.00 $ 8,550.00 18" CONC. PIPE LF 53 $ 85.00 $ 4,505.00 24" CONC. PIPE LF 10 $ 100.00 $ 1,000.00 CONCRETE CLASS A4 BOX CULVERT CY 46 $ 1,650.00 $ 75,900.00 CONCRETE CLASS A3 MISC CY 20 $ 1,600.00 $ 32,000.00 REINF STEEL LB 11,249 $ 2.00 $ 22,498.00 STRUCTURAL STEEL (DETENTION OUTLET) LB 120 $ 2.50 $ 300.00 DROP INLET DI-313, L=18' EA 1 $ 6,000.00 $ 6,000.00 DROP INLET DI-3B, L=16' EA 2 $ 6,000.00 $ 12,000.00 MANHOLE MH-2 LF 5 $ 750.00 $ 3,750.00 FRAME & COVER MH-1 EA 1 $ 800.00 $ 800.00 SUB -TOTAL $ 167,303.00 10% CONTINGENCY $ 16,730.30 DESIGN, CEI, VIDEO INSPECTION, AS-BUILTS, VDOT EXPENSES $ 15,966.70 TOTAL $ 200,000.00 Based on Cost Opinion prepared by Kimley-Horn and Assocs. 10 Jan 2019