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HomeMy WebLinkAboutWPO201600021 Review Comments WPO VSMP 2016-08-05COUNTY OF ALBEMARLE Department of Community Development 401 McIntire Road, Room 227 Charlottesville, Virginia 22902-4596 Phone (434) 296-5832 Fax (434) 972-4126 Project: Project Number: Plat/Plan preparer: Owner: Applicant/Developer: Plan received date: (Rev. 1) (Rev. 2) Date of comments: (Rev. 1) (Rev. 2) Reviewer: (Rev. 2) VSMP Permit plan review Woodlawn Subdivision —VSMP WP0201600021 Craig Kotarski, Clint Shifflett, Timmons Group 608 Preston Ave. #200, Charlottesville, VA 22903 craie.kotarski@timmons.com Marjorie M. Paul /2163 Bonaventura Drive, Vienna, VA 22181 Woodlawn Development, LLC /2180 Owensville Rd, Charlottesville, VA 22901 28 Mar 2016 13 Jun 2016 19 July 2016 16 May 2016 18 Jun 2016 5 Aug 2016 John Anderson (on behalf of Engineering) Matt Wentland A. Stormwater Pollution Prevention Plan (SWPPP) The SWPPP content requirements can be found in County Code section 17-405. A SWPPP must contain (1) a PPP, (2) an ESCP, (3) a SWMP, and (4) any TMDL measures necessary. Provide SWPPP, as with past projects. Template Attached. (Rev. 1) Partially Addressed. (Rev. 2) Addressed As follow-up: a. Sec. 9 —Sign Certification. Given recent difficulty (3 -month delay) acquiring signed SWPPP certification from this developer (Milestone Partners), additional review is contingent upon response to these comments —please address all comments with next plan submittal. b. Sec. 8 —`TBD' is unacceptable. Timmons personnel may be listed as placeholder qualified personnel. Qualified personnel will need to be listed before the first inspection. c. Sec. 6 —Critical PPP measures (Concrete washout, mortar mixing station, aboveground fuel container) are shown as rectangles without provision for containment. All locations discharge to graded slope /silt fence. This Exhibit requires care and improvement. All PPP measures should provide containment (barrier) limiting pollutant transport. PPP exhibit design should prevent runoff passing through or mixing with material/s in concrete washout, mortar mixing, or fuel storage locations. Engineering recommends meeting to discuss. Please contact County Engineer to arrange review meeting (J. Anderson unlikely to participate). d. Title SWPPP Exhibit PPP Exhibit. e. Show location of solid (non -hazardous) waste collection /dumpster on Exhibit. f. Show stockpile and spoils areas on Exhibit. Expand LOD, if necessary. g. Show staging area on Exhibit. B. VSMP: SWPPP: Stormwater Management Plan (WP0201600021) VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This plan is disapproved for reasons provided in comments below. The stormwater management plan content requirements can be Engineering Review Comments Page 2 of 6 found in County Code section 17-403 1. Title sheet: Revise index C5.0, C5.1 Site Plan to read Site Layout. VSMP approval does not approve a Site Plan. (Rev. 1) Addressed. 2. C1.0 -Show stream buffer. (Rev. 1) Addressed. 3. C4.0 -Critical Erosion Areas Note: Please include ref. to ACDSM, 8.A.2.: requirement for permanent stabilization hardier than grass for slopes steeper than 3:1. If label or plan note overlooked, disregard. (Rev. 1) Partially Addressed. Response misses intent of ACDSM, 8.A.2., which stipulates ground cover hardier than grass, which will not require mowing. Compare requirements at ACDSM with VESCH. Select and provide non -turf species hardier than grass which will not require mowing for slopes steeper than 3:1. ACDSM, 8.A.2: 2. For grass stabilization on constructed slopes, the maximum steepness is 3:1. Slopes steeper than 3:1 must be permanently stabilized with landscaping vegetation hardier than grass, which will not require mowing. VESCH, Table 3.32-D Low Maintenance Slope (Steeper than 3:1) - Kentucky 31 Tall Fescue - Common Bermudagrass - Red Top Grass Seasonal Nurse Crop Sericea Lespedeza ** (Rev. 2) Addressed. 4. C4.0 -Stormwater Runoff Consideration Note: Include ref. to Level I Extended Detention Facility, since VRRM .xls indicates Level I design. (Rev. 1) Addressed. 5. C4.0 -Sequence of Installation Note #9: Revise to read: "Once upslope areas are permanently stabilized, and with county inspector approval, remove culvert inlet protection, dewater sediment basin 1, remove saturated sediment basin floor material, and convert to SWM -1, Level I Extended Detention Facility." (Rev. 1) Addressed. 6. C4.0 -Sequence of Installation Notes: Ref. material required to raise floor elevation of sediment basin 4.5' to convert to SWM -1 (Level I ED Facility). (Rev. 1) Withdrawn. Redesign eliminates need for comment. As follow-up: Compare initial SB -1 (C4.1) with revised SB -1 dewatering structure design. Recommend restore initial design (perforated riser pipe). Provide SB -1 profile caption: Sediment basin (SB -1). Also, recommend against proposed 3" orifice at SWM -1 floor (sheet 7.2). Ref. initial design. Restore perforated riser. Proposed design is prone to immediate obstruction. This skews routing calculations, and undermines compliance. (Rev. 2) Addressed. 7. C5.0, C7.1 -Provide labels that dimension wood timber level spreaders. (Rev. 1) Partially Addressed. As follow-up: If two (2) stacked timbers are proposed, as appears to be the case, revise label. If re -bar steel anchoring is proposed, provide dimension labels (DIA /L). (Rev. 2) Addressed. 8. C5.0 -Label floor dimensions, SWM -1. (Rev. 1) Addressed. 9. C5.0 -Label forebay floor and gabion wall dimensions, SWM -1. (Rev. 1) Partially Addressed. As ollow- tp, C7.2: Provide galvanized steel post gabion basket dimension labels (depth of embedment, DIA, L, etc.) (Rev. 2) Addressed. 10. C5.0, C5.1 -Revise sheet title to Site Layout. (Rev. 1) Addressed. 11. C5.1 -Channel `B' Level Spreader 538.30' and 539.30' elevations do not appear to match LS detail, C7.2. Please check 0.5' vertical dimension on detail against plan. (Rev. 1) Addressed. 12. C7.0, C7.1 -Show /label Length of overland flow, shallow concentrated flow, and channel flow. (Rev. 1) Addressed. Note: Applicant response (9 Jun 2016) that "channel flow was not considered which results in a more conservative design" is at odds with hydrologic methodology. If t, increases, which occurs if channel flow is not considered, then intensity (I, see IDF chart) decreases, and Q decreases (Q =CIA); this Engineering Review Comments Page 3 of 6 is less conservative. Channel flow reduces time of concentration (t,), increasing intensity (in./hr.) and runoff, Q -this is a more conservative approach. Please help reviewer overcome any misperception. (Rev. 2) Addressed. 13. C7.1 -Provide restrictive covenant for 3.65 Ac. preserved wooded area. County can provide deeded easement template. (Rev. 1) Applicant: "We would prefer to provide this at the time of final Subdivision, similar to the approach that was taken at Dunlora V." Engineering has requested County Attorney's guidance on timing of restrictive covenant, and will work toward a helpful response to Applicant. (Rev. 2) Response Noted. This will not stand in the way of road plan approval, but a grading permit will not be issued until the easement has been recorded. 14. C7.1 -Post-development DA is inconsistent with VRRM values. (Rev. 1) Addressed. a. Impervious, C7.1 (DA #1, #1A, #113, #lU) =1.872 Ac. b. Impervious, VRRM: 1.77 Ac. c. Turf, C7.1 (DA #1, #IA, #1B, #1U) =24.14. d. Turf, VRRM: 17.59. e. If use C7.1 values with VRRM .xls, there appears to be a remaining phosphorus load =0.29 lb/yr ±. C7.2 15. Provide gabion wall detail. (Rev. 1) Partially Addressed. As follow-up, provide galvanized steel post depth of embedment, post dimensions (DIA, L). (Rev. 2) Addressed. 16. Grass channel A calculations: If use VRRM to check, Qa =Rv =0.43 in, rather than 0.23 in. [Please call to discuss.] (Rev. 1) Although discussed, Not Addressed. Applicant response to "Please refer to the VRRM summary" does not clarify discrepancy since the only VRRM summaries provided are: Site Data, DA `A', DA `B', and DA `C'. Further, routing computations do not appear to be source of 0.23 Rv value. A meeting may prove helpful. Engineering relies on VRRM channel and flood protection tab, and values. Text image of this tab for Woodlawn Subdivision is shown below. (Rev. 2) Addressed. 17. Grass channel B calculations: If use VRRM to check, Qa =Rv A.54 in, rather than 0.31 in. [Please call to discuss.] (Rev. 1) Although discussed, Not Addressed. See item #16, above. A meeting maybe helpful. Based on the use of Rum ff Reduction practices in the se lecled drainage areas, the spreadsheet calculates an adjusted RV­me.a and adjusted Curve Number. Drainage Area A Ascils B Soils C Soils D Soils ForesOOpen Space - undisturbed, protected farestlapen Area acres 0.00 0 O 0.88 8.88 space or reforested land CN 30 55 70 77 Managed Turf -disturbed, graded for yards or otherturft,he Area acres 0.00 2.53 0.00 0.00 mmedlmanaged CN 39 61 74 80 Area acres 0.00 022 0.00 0.00 Impemous Cover GN 98 98 98 98 Wei hted CN S 64 1 5.63 1- ear storm 2- year storm 10- ear storm RVo.� 1. d (in) with no Runoff Redudion 0.49 0.80 1.96 RVo. 1se.s jin)with Runoff Reduction1 0.43 1 8.75 11.91 Adjusted CN 1 53 1 0 1S3 Drainage Area B AsoiIs B Soils C Soils D Soils ForesVOpen Space - undisturbed, protected farestlapen Area acres 8.00 0.00 0.00 0.80 space or reforested land CN 30 55 78 77 Managed Turf -disturbed, graded for yards or otherturft,he Area acres 0.00 4.36 0.00 0.00 rn-edlmanaged CN 39 61 74 80 Impemous Cover Area acres 0.00 0.82 0.00 0 n CN 98 98 98 98 Weighted CN S 67 4.93 1-earatorm Z- ear storm 10. year storm RVoe , [in) with no Runoff Reduction 0.60 0.95 2. RVu�re wdjin) with Ru noff Reduction 0.54 0.89 21 .15 Adjusted CN 65 6fi (Rev. 1) Next 5 comments, Not Addressed. A meeting may prove help _(Rev. 2) Addressed. 18. Grass channel A calculations: Revise Q(1 -YR) to read Q(1"). Revise Maximum 1-YK Depth =4" to read Maximum 1" (runoff event) Depth =3" (Ref. VA DEQ Stormwater Design Specification No. 3, p. 11). (Rev. 1) Comment re -stated. (Rev. 2) Addressed. 19. Grass channel A calculations: Revise Q(1") =0.61 CFS to read =0.52 CFS, consistent with Hydrograph in calculations booklet. (Rev. 1) Response was to eliminate calculation altogether, and replace with Q2, Qjo calculations, which are less directly relevant. Restore/revise calculation in response to initial comment. (Rev. 2) Addressed. Engineering Review Comments Page 4 of 6 20. Revise grass channel A design if Q(1") Depth >3", as it appears to be. (Rev. 1) Q (1 -inch runoff event) depth reported =3.7". Max. 1 -IN runoff grass channel depth = 3". Ref. DEQ Spec. No. 3. Revise design. (Rev. 2) Addressed. 21. Grass channel B calculations: Revise Q(1 -YR) to read Q(1"). Revise Maximum 1 -YR Depth =4" to read Maximum 1" (runoff event) Depth =3". (Rev. 1) Not Addressed; see item #19, above. (Rev. 2) Addressed. 22. Revise grass channel B design if Q(1") Depth >3", as it appears to be. (Rev. 1) Comment re -stated. Note: County and Timmons have discussed possibility we are relying on different sources. Although DEQ notified local programs that revised VRRM spreadsheets were released (May 3), and Albemarle shared this notice with design community, VA DEQ Stormwater Design Specification No. 3 —Grass Channels appears unchanged. Ref. images below. Comments 18.-22. should be addressed; please provide design response. We believe a meeting to discuss comments may be helpful. Additional Follow -Up (New): Design Spec No. 3 requires a Min. of 6" of freeboard; revise design to provide 10 -yr peak flow rate containment within each grass channel, with a Min. of 6" of freeboard. (Rev. 2) Addressed. 23. Provide VRRM worksheet data that identifies DA routings through specific BMP measures, since not readily apparent (requires inference). (Rev. 1) Addressed. 24. Energy balance Eq.—Provide Rv pre -D =42,427 cu. ft.; Rv post -D =44,832 cu. ft. background calculations. (Rev. 1) Inadequately Addressed. Despite conversation, values remain perplexing. Ref. Calc. packet, Sub -catchment 4S, 6S (G.C.A, G.C.B); there are no easily traceable values that correspond with Rv values. Applicant: "Please refer to the 1 -year storm hydrographs within the calculation booklet. The volume was converted from Ac -Ft, to Cu. Ft." Despite reference and best effort, cannot make sense of Rv values. A meeting may prove helpful. (Rev. 2) Addressed. C. VSMP: SWPPP: Erosion Control Plan (WPO201600021) Virginia Code §62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This ESC plan is approved. 1. C4.1 —Sediment Basin #1 design data: dry storaLze provided at principal spillway crest listed as 300 cy (<761.1 cy dry storage required). Misprir. (Rev. 1) Addressed. 2. C4.1 —Sediment Basin #1 design data: depth of water at (emergency) spillway crest listed as 8.2', but using crest and bottom of basin elevations, depth appears =9.2'. (Rev. 1) Addressed via sediment basin redesign. C4.2 3. Label floor dimensions, SB -1. (Rev. 1) Addressed. 4. Provide dimensions for stilling basins A, B. (Rev. 1) Addressed. 5. Provide dimensions for culvert A, B outlet protection, if different from stilling basin dimensions. (Rev. 1) Addressed. "The outlet protection dimensions are the same as the stilling basin dimensions." 6. Limits of disturbance appear impractical as drawn. Expand LOD to accommodate typical construction equipment, especially on individual Lots (dwellings, septic field, driveways). Equipment operators will likely not consult plan, and if they do, may inadvertently or unwillingly be unable to perform fine grading, or grading required to level site, or construct driveways /septic fields. Expanding LOD somewhat (up to 9.99 Ac.) has no effect on permit application or VSMP plan review fees, although increased LOD may increase annual permit maintenance fee ($100/Ac.). (Rev. 1) Addressed. As follow-up: Recommend consider stockpile /spoils /staging area requirements, and revise LOD, as necessary. Also, see SWPPP comments, above. 7. Recommend Notes and labels to prevent equipment or construction activity impacts to Areas to be used for SWM BMP grass channels A, B. (Rev. 1) Addressed. 8. Recommend include Sequence of Installation Note (C4.0) that reflects C4.2 Note: `Finalize grass channel grading and groundcover only after contributing drainage area is stabilized.' (Rev. 1) Addressed. 9. No ESC measures appear to be provided on individual Lots. It is unclear if driveways and home sites are to be built with this WPO. If not, please label build sites for illustration only, with ESC measures (each Lot) Engineering Review Comments Page 5 of 6 to be provided by builder /others.' If build sites, driveways, and septic fields are to be addressed under this WPO Plan, then provide required ESC measures required to grade Lots. Provide SF, check dams, etc. (Rev. 1) Addressed. 10. Recommend check dams along west side Woodlawn Rd. given 24' vertical interval between Lot 1 driveway and culvert B INV IN. (Rev. 1) Addressed. 11. Estimate stream buffer impact (SF); prepare /submit Mitigation Plan. (Rev. 1) Addressed. 12. Eliminate SWM -1 proposed contours. (Rev. 1) Addressed. 13. Provide SF, east side Woodlawn Rd. (Rev. 1) Addressed. C4.3 14. Lot 6 —Provide ES for 15" DIA driveway culvert pipe. (Rev. 1) Addressed. 15. Provide individual Lot ESC measures. Also, item #9, above. (Rev. 1) Addressed. 16. Provide check dams, Lot 5 and 6 driveways. (Rev. 1) Addressed. 17. C5.1 —Coordinate Lot 6 driveway design with ACF&R. With opposing 12.6 and 9.4% grades, newer fire engine units with 13- 1/8" clearance from tow hook to ground may have limited access to this Lot. This may require driveway profile. (Rev. 1) Addressed. Ref. ACF&R email to Applicant: 6/16/2016 10:43 AM; no concerns expressed. No portion of Lot 6 driveway exceeds 16%. Engineering plan review staff are available from 2-4 PM on Thursdays, should you require a meeting to discuss this review. Plan review staff is available at 434-296-5832 should you have any questions —request Engineering. Process: After approval, plans will need to be bonded. The bonding process is begun by submitting a bond estimate request form and fee to the Department of Community Development. One of the plan reviewers will prepare estimates and check parcel and easement information based on the approved plans. The County's Management Analyst will prepare bond agreement forms, which will need to be completed by the owner and submitted along with cash, certificates or sureties for the amounts specified. The agreements will need to be approved and signed by the County Attorney and County Engineer. This may take 2-4 weeks to obtain all the correct signatures and forms. Stormwater Management Facilities Maintenance agreements will also need to be completed and recorded. The County's Management Analyst or other staff will prepare the forms and check for ownership and signature information. The completed forms will need to be submitted along with court recording fees. After bonding and agreements are complete, county staff will need to enter project information in a DEQ database for state application processing. DEQ will review the application information based on local VSMP authority approval. At this time, the DEQ portion of the application fees will need to be paid directly to the state. For fastest processing, this is done electronically with the emails provided on the application. DEQ should notify applicants with instructions on how to pay fees. When DEQ approves the application, they will issue a permit coverage letter. This should be copied to the county. After DEQ coverage is issued, via the coverage letter, the County can hold a pre -construction conference. Applicants will need to request a pre -construction conference by completing a form, and pay the remainder of the application fee. The form identifies the contractor and responsible land disturber, and the fee remaining to be paid. This will be checked by county staff, and upon approval, a pre -construction conference will be scheduled with the County inspector. At the pre -construction conference, should everything proceed satisfactorily, a joint VSMP and grading permit will be issued by the County so that work may begin. County forms can be found on the county website forms center under engineering; http://www.albemarle.org/deptfonns.asp?department=cdenjZMTo Engineering Review Comments Page 6 of 6 Thank you (Please contact Frank Pohl, County Engineer, to schedule plan review meeting — 434.296-5832 —x7914) New tel. # -434.872-4501 —0069 (J. Anderson) WP0201600021 _W oodlawn_V SMP_080516rev2 COUNTY OF ALBEMARLE Department of Community Development 401 McIntire Road, Room 227 Charlottesville, Virginia 22902-4596 Phone (434) 296-5832 Fax (434) 972-4126 VSMP Permit plan review Project: Woodlawn Subdivision —VSMP Project Number: WP0201600021 Plat/Plan preparer: Craig Kotarski, Clint Shifflett, Timmons Group 608 Preston Ave. #200, Charlottesville, VA 22903 craig.kotarski(ctimmons.com Owner: Marjorie M. Paul /2163 Bonaventura Drive, Vienna, VA 22181 Applicant/Developer: Woodlawn Development, LLC /2180 Owensville Rd, Charlottesville, VA 22901 Plan received date: 28 Mar 2016 (Rev. 1) 13 Jun 2016 Date of comments: 16 May 2016 (Rev. 1) 18 Jun 2016 Reviewer: John Anderson (on behalf of Engineering) A. Stormwater Pollution Prevention Plan (SWPPP) The SWPPP content requirements can be found in County Code section 17-405. A SWPPP must contain (1) a PPP, (2) an ESCP, (3) a SWMP, and (4) any TMDL measures necessary. Provide SWPPP, as with past projects. Template Attached. (Rev. 1) Partially Addressed. Asfollow-up: a. Sec. 9—Sijzn Certifcation. Given recent difficulty (3 -month delay) acquiring signed SWPPP certification from this developer (Milestone Partners), additional review is contingent upon response to these comments —please address all comments with next plan submittal. b. Sec. 8 —`TBD' is unacceptable. Timmons personnel may be listed as placeholder qualified personnel. c. Sec. 6 —Critical PPP measures (Concrete washout, mortar mixing station, aboveground fuel container) are shown as rectangles without provision for containment. All locations discharge to graded slope /silt fence. This Exhibit requires care and improvement. All PPP measures should provide containment (barrier) limiting pollutant transport. PPP exhibit design should prevent runoff passing through or mixing with material/s in concrete washout, mortar mixing, or fuel storage locations. Engineering recommends meeting to discuss. Please contact County Engineer to arrange review meeting (J. Anderson unlikely to participate). d. Title SWPPP Exhibit PPP Exhibit. e. Show location of solid (non -hazardous) waste collection /dumpster on Exhibit. f. Show stockpile and spoils areas on Exhibit. Expand LOD, if necessary. g. Show staging area on Exhibit. B. VSMP: SWPPP: Stormwater Management Plan (WP0201600021) VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This plan is disapproved for reasons provided in comments below. The stormwater management plan content requirements can be found in County Code section 17-403 Title sheet: Revise index C5.0, C5.1 Site Plan to read Site Layout. VSMP approval does not approve a Site Plan. (Rev. 1) Addressed. Engineering Review Comments Page 2 of 6 2. C1.0 -Show stream buffer. (Rev. 1) Addressed. 3. C4.0 -Critical Erosion Areas Note: Please include ref. to ACDSM, 8.A.2.: requirement for permanent stabilization hardier than grass for slopes steeper than 3:1. If label or plan note overlooked, disregard. (Rev. 1) Partially Addressed. Response misses intent of ACDSM, 8.A.2., which stipulates ground cover hardier than grass, which will not require mowing. Compare requirements at ACDSM with VESCH. Select and provide non -turf species hardier than grass which will not require mowing for slopes steeper than 3:1. ACDSM, 8.A.2: 2. For grass stabilization on constructed slopes, the maximum steepness is 3:1. Slopes steeper than 3:1 must be permanently stabilized with landscaping vegetation hardier than grass, which will not require mowing. VESCH, Table 3.32-D Low Maintenance Slope (Steeper., than 3:1) - Kentucky 31 Tall Fescue - Common Bermudagrass - Red Top Grass - Seasonal Nurse Crop - Sericea Lespedeza * * 4. C4.0-Stormwater Runoff Consideration Note: Include ref to Level I Extended Detention Facility, since VRRM .xIs indicates Level I design. (Rev. 1) Addressed. 5. C4.0 -Sequence oflnstallation Note #9: Revise to read: "Once upslope areas are permanently stabilized, and with county inspector approval, remove culvert inlet protection, dewater sediment basin 1, remove saturated sediment basin floor material, and convert to SWM -1, Level I Extended Detention Facility." (Rev. 1) Addressed. 6. C4.0 -Sequence of Installation Notes: Ref material required to raise floor elevation of sediment basin 4.5' to convert to SWM -1 (Level I ED Facility). (Rev. 1) Withdrawn. Redesign eliminates need for comment. As follow-up: Compare initial SB -1 (C4.1) with revised SB -1 dewatering structure design. Recommend restore initial design (perforated riser pipe). Provide SB -1 profile caption: Sediment basin (SB -1). Also, recommend against proposed 3" orifice at SWM -1 floor (sheet 7.2). Ref initial design. Restore perforated riser. Proposed design is prone to immediate obstruction. This skews routing calculations, and undermines compliance. 7. C5.0, C7.1 -Provide labels that dimension wood timber level spreaders. (Rev. 1) Partially Addressed. As follow-up: If two (2) stacked timbers are proposed, as appears to be the case, revise label. If re -bar steel anchoring is proposed, provide dimension labels (DIA /L). 8. C5.0 -Label floor dimensions, SWM -1. (Rev. 1) Addressed. 9. C5.0 -Label forebay floor and gabion wall dimensions, SWM -1. (Rev. 1) Partially Addressed. Asfollow- up, C7.2: Provide galvanized steel post gabion basket dimension labels (depth of embedment, DIA, L, etc.) 10. C5.0, C5.1 -Revise sheet title to Site Layout. (Rev. 1) Addressed. 11. C5.1 -Channel `B' Level Spreader 538.30' and 539.30' elevations do not appear to match LS detail, C7.2. Please check 0.5' vertical dimension on detail against plan. (Rev. 1) Addressed. 12. C7.0, C7.1 -Show /label Length of overland flow, shallow concentrated flow, and channel flow. (Rev. 1) Addressed. Note: Applicant response (9 Jun 2016) that "channel flow was not considered which results in a more conservative design" is at odds with hydrologic methodology. If t, increases, which occurs if channel flow is not considered, then intensity (I, see IDF chart) decreases, and Q decreases (Q =CIA); this is less conservative. Channel flow reduces time of concentration (Q, increasing intensity (in./hr.) and runoff, Q -this is a more conservative approach. Please help reviewer overcome any misperception. 13. C7.1 -Provide restrictive covenant for 3.65 Ac. preserved wooded area. County can provide deeded easement template. (Rev. 1) Applicant: "We would prefer to provide this at the time of final Subdivision, similar to the approach that was taken at Dunlora V." Engineering has requested County Attorney's guidance on timing of restrictive covenant, and will work toward a helpful response to Applicant. 14. C7.1 -Post-development DA is inconsistent with VRRM values. (Rev. 1) Addressed. a. Impervious, C7.1 (DA #1, #IA, #113, #IU) =1.872 Ac. Engineering Review Comments Page 3 of 6 b. Impervious, VRRM: 1.77 Ac. c. Turf, C7.1 (DA #1, #IA, #113, #lU) =24.14. d. Turf, VRRM: 17.59. e. If use C7.1 values with VRRM .xls, there appears to be a remaining phosphorus load =0.29 lb C7.2 15. Provide gabion wall detail. (Rev. 1) Partially Addressed. As follow-up, provide galvanized steel post depth of embedment, post dimensions (DIA, L). 16. Grass channel A calculations: If use VRRM to check, Qa =Rv =0.43 in, rather than 0.23 in. [Please call to discuss.] (Rev. 1) Although discussed, Not Addressed. Applicant response to "Please refer to the VRRM summary" does not clarify discrepancy since the only VRRM summaries provided are: Site Data, DA `A', DA `13% and DA `C'. Further, routing computations do not appear to be source of 0.23 Rv value. A meeting may prove helpful. Engineering relies on VRRM channel and flood protection tab, and values. Text image of this tab for Woodlawn Subdivision is shown below. 17. Grass channel B calculations: If use VRRM to check, Qa =Rv =0.54 in, rather than 0.31 in. [Please call to discuss.] (Rev. 1) Although discussed, Not Addressed. See item #16, above. A meeting may be helpful. Based on the use of Runoff Reduction practices in the selected drainage areas, the spreadsheet calculates an adjusted RV ­.,o and adjusted Curve Number. Drainage Area A FA soils B Soils C Soils D Soils _ ForesUOpen Space - undisturbed, protected forestlopen Area acres 0.00 0.00 0.00 0.00 space or reforested land CN 30 55 70 77 Managed Turf -disturbed, graded for yards or othertudtohs Area acres 0.00 2.53 0.00 0.00 mmedlmanaged CN 39 61 74 80 Area acres 0.00 022 0.00 0.00 Impernous Cover GN 98 98 98 98 Wei hted CN S 64 5.63 1- earstorm 2 -year Morin 10- earstorm RVu., 1. d (in) with no Runoff Reduction 0.49 0.80 1.96 RVu.,. d(in) with Runoff Reduction 0.43 0.75 1.91 Adjusted CN 0 0 0 Drainage Area B FA soils B Soils C Soils D Soils ForestJOpen Space - undisturhed, protected farestlapen Area acres 0.00 0.00 0.00 0.00 space or reforested land CN 30 55 70 TT Managed Turf -disturbed, graded for yards or othertudtobs Area acres 0.00 4.36 0.00 0.00 mowedlmanaged CN 39 61 74 80 Impemeus Cover Area acres 0.00 0.82 0.00 0.00 CN 98 98 98 98 Weighted CN S 67 4.93 1- earstorm Z- earstorm 10- earstorm RVu., 1. d (in) with no Runoff Reduction 0.60 0.95 221 RVo� ,,,, tin) with Runoff Reduction 0.54 0.89 2.15 Adjusted CN 65 bb (Rev. 1) Next 5 comments, Not Addressed. A meeting may prove helpful. 18. Grass channel A calculations: Revise Q(1 -YR) to read Q(1"). Revise Maximum 1 -YR Depth =4" to read Maximum 1" (runoff event) Depth =3" (Ref. VA DEQ Stormwater Design Specification No. 3, p. 11). (Rev. 1) Comment re -stated. 19. Grass channel A calculations: Revise Q(1") =0.61 CFS to read =0.52 CFS, consistent with Hydrograph in calculations booklet. Rev. 1 Response was to eliminate calculation altogether, and replace with Q2, Q10 calculations, which are less directly relevant. Restore/revise calculation in response to initial comment. 20. Revise grass channel A design if Q(1") Depth >3", as it appears to be. Rev. 1 Q (1 -inch runoff event) depth reported =3.7". Max. 1 -IN runoff grass channel depth= 3". Ref DEQ Spec. No. 3. Revise design. 21. Grass channel B calculations: Revise Q(1 -YR) to read Q(1"). Revise Maximum 1 -YR Depth =4" to read Maximum 1" (runoff event) Depth =3". (Rev. 1) Not Addressed; see item #19, above. 22. Revise grass channel B design if Q(1") Depth >3", as it appears to be. (Rev. 1) Comment re -stated. Note: County and Timmons have discussed possibility we are relying on different sources. Although DEQ notified local programs that revised VRRM spreadsheets were released (May 3), and Albemarle shared this notice with design community, VA DEQ Stormwater Design Specification No. 3 -Grass Channels appears unchanged. Ref images below. Comments 18.-22. should be addressed; please provide design response. We believe a meeting to discuss comments may be helpful. Additional Follow -Up (New): Design Spec No. 3 requires a Min. of 6" of freeboard; revise design to provide 10 -yr peak flow rate containment within each grass channel, with a Min. of 6" of freeboard. Engineering Review Comments Page 4 of 6 DEQ (later, 5 -MU Notification): Announcing - Updated Runoff Reduction Spreadsheet (v 3.0) DEQ has updated the Virginia Runoff Reduction Method (VRRM) Compliance Spreadsheets, and User's Guide (Version 3.0, April 2016). The update improves functionality and summary reporting. It also fixes various inconsistencies, and reduces trr number of spreadsheets from four to two; New Development and Rede%•elopment. See the User Guide for detailed instructions and a thorough explar.atlor. of the spreadsheet logic, equations, and reference information. The spreadsheets, user guide and associated guidance memo are available on the Water Permit Guidance a4ebpage: 16-2001, and are also posted on the BMP Clearinghouse website. Coming Soon! VRRM Webinars To support the roll-out of the updated VRRM spreadsheets and user guide, DEQ will be scheduling a series of targeted webinars. Dates and times will be announced soon. VA DEQ BMP Specification No. 3 Hydraulic capacity should be verified using Manning's Equation or an accepted equivalent method, such as erodibility factors and vegetal retardance (NOVA 2007). o The Flow Depth for the peak treatment volume (1 -inch rainfall) should be maintained at 3 inches or less. o Manning's "n" value for grass channels should be 0.2 for flow depths up to 4 inches, decreasing to 0.03 at a depth of 12 inches (which would apply to the 2 -year and 10 -year storms if an on-line application — NOVA, 2007; Haan et. al, 1994). o Peak Flow Rates for the 2 -year and 10 -year frequency storms must be non-erosive, in accordance with Table 3.3, or subject to a site-specific analysis of the channel lining material and vegetation; and the l0 -year peak flow rate must be contained within the channel banks (with a minimum of 6 inches of freeboard). (NOTE: After the new Virginia Stormwater Management Regulation revisions take effect, the above requirement will be driven by the SWM Regulations (4 VAC 50-60-66 A 1 and B 1), which will supersede the MS -19 criteria of the Virginia E&S Control Regulations.) 23. Provide VRRM worksheet data that identifies DA routings through specific BMP measures, since not readily apparent (requires inference). (Rev. 1) Addressed. 24. Energy balance Eq.—Provide Rv pre -D =42,427 cu. ft.; Rv post -D =44,832 cu. ft. background calculations. (Rev. 1) Inadequately Addressed. Despite conversation, values remain perplexing. Ref. Calc. packet, Sub -catchment 4S, 6S (G.C.A, G.C.B); there are no easily traceable values that correspond with Rv values. Applicant: "Please refer to the 1 -year storm hydrographs within the calculation booklet. The volume was converted from Ac -Ft, to Cu. Ft." Despite reference and best effort, cannot make sense of Rv values. A meeting may prove helpful. C. VSMP: SWPPP: Erosion Control Plan (WP0201600021) Virginia Code §62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This ESC plan is aRproved. 1. C4.1 —Sediment Basin 91 design data: dry storage provided at principal spillway crest listed as 300 cy (<761.1 cy dry storage required). Misprint? (Rev. 1) Addressed. 2. C4.1 —Sediment Basin #1 design data: depth of water at (emergency) spillway crest listed as 8.2', but using crest and bottom of basin elevations, depth appears =9.2'. (Rev. 1) Addressed via sediment basin redesign. C4.2 Engineering Review Comments Page 5 of 6 3. Label floor dimensions, S13-1. (Rev. 1) Addressed. 4. Provide dimensions for stilling basins A, B. (Rev. 1) Addressed. 5. Provide dimensions for culvert A, B outlet protection, if different from stilling basin dimensions. (Rev. 1) Addressed. "The outlet protection dimensions are the same as the stilling basin dimensions." 6. Limits of disturbance appear impractical as drawn. Expand LOD to accommodate typical construction equipment, especially on individual Lots (dwellings, septic field, driveways). Equipment operators will likely not consult plan, and if they do, may inadvertently or unwillingly be unable to perform fine grading, or grading required to level site, or construct driveways /septic fields. Expanding LOD somewhat (up to 9.99 Ac.) has no effect on permit application or VSMP plan review fees, although increased LOD may increase annual permit maintenance fee ($100/Ac.). (Rev. 1) Addressed. Asfollow-up: Recommend consider stockpile /spoils /staging area requirements, and revise LOD, as necessary. Also, see SWPPP comments, above. 7. Recommend Notes and labels to prevent equipment or construction activity impacts to Areas to be used for SWM BMP grass channels A, B. (Rev. 1) Addressed. 8. Recommend include Sequence of Installation Note (C4.0) that reflects C4.2 Note: `Finalize grass channel grading and groundcover only after contributing drainage area is stabilized.' (Rev. 1) Addressed. 9. No ESC measures appear to be provided on individual Lots. It is unclear if driveways and home sites are to be built with this WPO. If not, please label build sites for illustration only, with ESC measures (each Lot) to be provided by builder /others.' If build sites, driveways, and septic fields are to be addressed under this WPO Plan, then provide required ESC measures required to grade Lots. Provide SF, check dams, etc. (Rev. 1) Addressed. 10. Recommend check dams along west side Woodlawn Rd. given 24' vertical interval between Lot 1 driveway and culvert B INV IN. (Rev. 1) Addressed. 11. Estimate stream buffer impact (SF); prepare /submit Mitigation Plan. (Rev. 1) Addressed. 12. Eliminate SWM -1 proposed contours. (Rev. 1) Addressed. 13. Provide SF, east side Woodlawn Rd. (Rev. 1) Addressed. C4.3 14. Lot 6 —Provide ES for 15" DIA driveway culvert pipe. (Rev. 1) Addressed. 15. Provide individual Lot ESC measures. Also, item #9, above. (Rev. 1) Addressed. 16. Provide check dams, Lot 5 and 6 driveways. (Rev. 1) Addressed. 17. C5.1 —Coordinate Lot 6 driveway design with ACF&R. With opposing 12.6 and 9.4% grades, newer fire engine units with 13- 1/8" clearance from tow hook to ground may have limited access to this Lot. This may require driveway profile. (Rev. 1) Addressed. Ref. ACF&R email to Applicant: 6/16/2016 10:43 AM; no concerns expressed. No portion of Lot 6 driveway exceeds 16%. Engineering plan review staff are available from 2-4 PM on Thursdays, should you require a meeting to discuss this review. Plan review staff is available at 434-296-5832 should you have any questions —request Engineering. Process: After approval, plans will need to be bonded. The bonding process is begun by submitting a bond estimate request form and fee to the Department of Community Development. One of the plan reviewers will prepare estimates and check parcel and easement information based on the approved plans. The County's Management Analyst will prepare bond agreement forms, which will need to be completed by the owner and submitted along with cash, certificates or sureties for the amounts specified. The agreements will need to be approved and signed by the County Attorney and County Engineer. This may take 2-4 weeks to obtain all the correct signatures and forms. Stormwater Management Facilities Maintenance agreements will also need to be completed and recorded. The County's Management Analyst or other staff will prepare the forms and check for ownership and signature Engineering Review Comments Page 6 of 6 information. The completed forms will need to be submitted along with court recording fees. After bonding and agreements are complete, county staff will need to enter project information in a DEQ database for state application processing. DEQ will review the application information based on local VSMP authority approval. At this time, the DEQ portion of the application fees will need to be paid directly to the state. For fastest processing, this is done electronically with the emails provided on the application. DEQ should notify applicants with instructions on how to pay fees. When DEQ approves the application, they will issue a permit coverage letter. This should be copied to the county. After DEQ coverage is issued, via the coverage letter, the County can hold a pre -construction conference. Applicants will need to request a pre -construction conference by completing a form, and pay the remainder of the application fee. The form identifies the contractor and responsible land disturber, and the fee remaining to be paid. This will be checked by county staff, and upon approval, a pre -construction conference will be scheduled with the County inspector. At the pre -construction conference, should everything proceed satisfactorily, a joint VSMP and grading permit will be issued by the County so that work may begin. County forms can be found on the county website forms center under engineering; htW://www.albemarle.org/deptforms.asp?department--cdengnoo Thank you (Please contact Frank Pohl, County Engineer, to schedule plan review meeting — 434.296-5832 —x7914) New teL # -434.872-4501 —x3069 (J. Anderson) WP0201600021—Woodlawn VSMP-061816rev1 COUNTY OF ALBEMARLE Department of Community Development 401 McIntire Road, Room 227 Charlottesville, Virginia 22902-4596 Phone (434) 296-5832 Fax (434) 972-4126 VSMP Permit plan review Project: Woodlawn Subdivision —VSMP Project Number: WP0201600021 Plat/Plan preparer: Craig Kotarski, Clint Shifflett, Timmons Group 608 Preston Ave. #200, Charlottesville, VA 22903 craig.kotarski(ctimmons.com Owner: Marjorie M. Paul /2163 Bonaventura Drive, Vienna, VA 22181 Applicant/Developer: Woodlawn Development, LLC /2180 Owensville Rd, Charlottesville, VA 22901 Plan received date: 28 Mar 2016 Date of comments: 16 May 2016 Reviewer: John Anderson A. Stormwater Pollution Prevention Plan (SWPPP) The SWPPP content requirements can be found in County Code section 17-405. A SWPPP must contain (1) a PPP, (2) an ESCP, (3) a SWMP, and (4) any TMDL measures necessary. 1. Provide SWPPP, as with past projects. Template Attached. B. VSMP: SWPPP: Stormwater Management Plan (WP0201600021) VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This plan is disapproved for reasons provided in comments below. The stormwater management plan content requirements can be found in County Code section 17-403 1. Title sheet: Revise index C5.0, C5.1 Site Plan to read Site Layout. VSMP approval does not approve a Site Plan. 2. C 1.0 —Show stream buffer. 3. C4.0 —Critical Erosion Areas Note: Please include ref to ACDSM, 8.A.2.: requirement for permanent stabilization hardier than grass for slopes steeper than 3:1. If label or plan note overlooked, disregard. 4. C4.0—Stormwater Runoff Consideration Note: Include ref. to Level I Extended Detention Facility, since VRRM .xls indicates Level I design. 5. C4.0 —Sequence of Installation Note #9: Revise to read: "Once upslope areas are permanently stabilized, and with county inspector approval, remove culvert inlet protection, dewater sediment basin 1, remove saturated sediment basin floor material, and convert to SWM -1, Level I Extended Detention Facility." 6. C4.0 —Sequence of Installation Notes: Ref. material required to raise floor elevation of sediment basin 4.5' to convert to SWM -1 (Level I ED Facility). 7. C5.0, C7.1 —Provide labels that dimension wood timber level spreaders. 8. C5.0 —Label floor dimensions, SWM -1. 9. C5.0 —Label forebay floor and gabion wall dimensions, SWM -1. 10. C5.0, C5.1 —Revise sheet title to Site Layout. 11. C5.1 —Channel `B' Level Spreader 538.30' and 539.30' elevations do not appear to match LS detail, C7.2. Please check 0.5' vertical dimension on detail against plan. 12. C7.0, C7.1 —Show /label Length of overland flow, shallow concentrated flow, and channel flow. Engineering Review Comments Page 2 of 4 13. C7.1 -Provide restrictive covenant for 3.65 Ac. preserved wooded arca. County can provide deeded easement template. 14. C7.1 -Post-development DA is inconsistent with VRRM values. a. Impervious, C7.1 (DA #1, #lA, #113, #1U) =1.872 Ac. b. Impervious, VRRM: 1.77 Ac. c. Turf, C7.1 (DA #1, #IA, #1B, #IU) =24.14. d. Turf, VRRM: 17.59. e. If use C7.1 values with VRRM .xls, there appears to be a remaining phosphorus load =0.29 lb/yr f. C7.2 15. Provide gabion wall detail. 16. Grass channel A calculations: If use VRRM to check, Qa =Rv =0.43 in, rather than 0.23 in. [Please call to discuss.] 17. Grass channel B calculations: If use VRRM to check, Qa =Rv =0.54 in, rather than 0.31 in. [Please call to discuss.] Based on the use or Runoff Reduction practices in the selected drainage areas, the spreadsheet calculates an adjusted RV ­ .,d and adjusted Cu- Number. Drainage Area A Asoils B Soils C Soils D Soils ForestlOpen Space - undisturbed, protected '0res1'0penffArs 9.06 0.08 0.00 0.00 space or reforested land 30 55 70 77 Managed Turf- disturbed, graded ',rds or ethertudtobe 0.00 2.53 0.00 0.00 mowedlmanaged 39 61 74 80 0.00 0.22 000 0.00 mpemcus Cover 98 98 98 98 Weighted CN S 64 5.63 1- ear storm 2- ear storm 10- ear storm RVo� ,d (in) with no Runoff Reduction 0 49 0.80 1.96 RVn ,djin) with Ru noff Reduction 043 0.75 191 Adjusted CN 53 53 1 53 Drainage Area B Asoils B Soils C Soils D Soils ForeeUOpen Space - undisturbed, protected feresffopen Area acres 0.00 0.00 0.00 0.00 space or reforested land CN 30 55 70 77 Managed Turf -disturbed, graded for yards or ethertudto he Area acres 8.08 4.36 8.88 8 00 mowedlmanaged CN 39 61 74 80 Imperwaus Cover Area acres 0.00 0.82 000 0.00 CN 98 98 98 98 Weighted CN 5 67 1- ear storm 2- ear storm 10- ear storm RVne pe (in) with no Runoff Reduction 0.60 0.95 221 RVn�„e 'jin)with Runoff Reduction 0.54 1 Q 2.15 Adjusted CN 65 18. Grass channel A calculations: Revise Q(1 -YR) to read Q(1"). Revise Maximum 1 -YR Depth =4" to read Maximum 1" (runoff event) Depth =3" (Ref. VA DEQ Stormwater Design Specification No. 3, p. 11). 19. Grass channel A calculations: Revise Q(1") =0.61 CFS to read =0.52 CFS, consistent with Hydrograph in calculations booklet. 20. Revise grass channel A design if Q(1 ") Depth >3", as it appears to be. 21. Grass channel B calculations: Revise Q(1 -YR) to read Q(1"). Revise Maximum 1 -YR Depth =4" to read Maximum 1" (runoff event) Depth =3". 22. Revise grass channel B design if Q(1 ") Depth >3", as it appears to be. 23. Provide VRRM worksheet data that identifies DA routings through specific BMP measures, since not readily apparent (requires inference). 24. Energy balance Eq. -Provide Rv pre -D =42,427 cu. ft.; Rv post -D =44,832 cu. ft. background calculations. C. VSMP: SWPPP: Erosion Control Plan (WP0201600021) Virginia Code §62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan is disapproved for reasons provided in comments below. The erosion control plan content requirements can be found in County Code section 17-402. 1. C4.1 -Sediment Basin #1 design data: dry storage provided at principal spillway crest listed as 300 cy (<761.1 cy dry storage required). Misprint? 2. C4.1 -Sediment Basin #1 design data: depth of water at (emergency) spillway crest listed as 8.2', but using crest and bottom of basin elevations, depth appears =9.2'. Engineering Review Comments Page 3 of 4 C4.2 3. Label floor dimensions, S13-1. 4. Provide dimensions for stilling basins A, B. 5. Provide dimensions for culvert A, B outlet protection, if different from stilling basin dimensions. 6. Limits of disturbance appear impractical as drawn. Expand LOD to accommodate typical construction equipment, especially on individual Lots (dwellings, septic field, driveways). Equipment operators will likely not consult plan, and if they do, may inadvertently or unwillingly be unable to perform fine grading, or grading required to level site, or construct driveways /septic fields. Expanding LOD somewhat (up to 9.99 Ac.) has no effect on permit application or VSMP plan review fees, although increased LOD may increase annual permit maintenance fee ($100/Ac.). 7. Recommend Notes and labels to prevent equipment or construction activity impacts to Areas to be used for SWM BMP grass channels A, B. 8. Recommend include Sequence oflnstallation Note (C4.0) that reflects C4.2 Note: `Finalize grass channel grading and groundcover only after contributing drainage area is stabilized.' 9. No ESC measures appear to be provided on individual Lots. It is unclear if driveways and home sites are to be built with this WPO. If not, please label build sites `for illustration only, with ESC measures (each Lot) to be provided by builder /others.' If build sites, driveways, and septic fields are to be addressed under this WPO Plan, then provide required ESC measures required to grade Lots. Provide SF, check dams, etc. 10. Recommend check dams along west side Woodlawn Rd. given 24' vertical interval between Lot 1 driveway and culvert B INV IN. 11. Estimate stream buffer impact (SF); prepare /submit Mitigation Plan. 12. Eliminate SWM -1 proposed contours. 13. Provide SF, east side Woodlawn Rd. C4.3 14. Lot 6 —Provide ES for 15" DIA driveway culvert pipe. 15. Provide individual Lot ESC measures. Also, item #9, above. 16. Provide check dams, Lot 5 and 6 driveways. 17. C5.1 —Coordinate Lot 6 driveway design with ACF&R. With opposing 12.6 and 9.4% grades, newer fire engine units with 13- 1/8" clearance from tow hook to ground may have limited access to this Lot. This may require driveway profile. Engineering plan review staff are available from 2-4 PM on Thursdays, should you require a meeting to discuss this review. Plan review staff are also available at 434-296-5832 (-x3069) should you have questions. Process: After approval, plans will need to be bonded. The bonding process is begun by submitting a bond estimate request form and fee to the Department of Community Development. One of the plan reviewers will prepare estimates and check parcel and easement information based on the approved plans. The County's Management Analyst will prepare bond agreement forms, which will need to be completed by the owner and submitted along with cash, certificates or sureties for the amounts specified. The agreements will need to be approved and signed by the County Attorney and County Engineer. This may take 2-4 weeks to obtain all the correct signatures and forms. Stormwater Management Facilities Maintenance agreements will also need to be completed and recorded. The County's Management Analyst or other staff will prepare the forms and check for ownership and signature information. The completed forms will need to be submitted along with court recording fees. After bonding and agreements are complete, county staff will need to enter project information in a DEQ database for state application processing. DEQ will review the application information based on local VSMP authority approval. At this time, the DEQ portion of the application fees will need to be paid directly to the state. For fastest processing, this is done electronically with the emails provided on the application. DEQ should notify applicants Engineering Review Comments Page 4 of 4 with instructions on how to pay fees. When DEQ approves the application, they will issue a permit coverage letter. This should be copied to the county. After DEQ coverage is issued, via the coverage letter, the County can hold a pre -construction conference. Applicants will need to request a pre -construction conference by completing a form, and pay the remainder of the application fee. The form identifies the contractor and responsible land disturber, and the fee remaining to be paid. This will be checked by county staff, and upon approval, a pre -construction conference will be scheduled with the County inspector. At the pre -construction conference, should everything proceed satisfactorily, a joint VSMP and grading permit will be issued by the County so that work may begin. County forms can be found on the county website forms center under engineering; http://www. albemarle. orgJdeptforms. asp?department=cdengwUo Thank you -434.296-5832 —0069 WP0201600021 WOOdlawn_VSMP_051616