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HomeMy WebLinkAboutWPO201800030 Correspondence 2018-10-18TIMMONS GROUP YOUR VISION ACHIEVED THROUGH OURS. October 12, 2018 County of Albemarle Dept. of Community Dev. 401 McIntire Rd. Charlottesville, VA 22902 608 Preston Avenue P 434.295.5624 Suite 200 F 434.295.8317 Charlottesville, VA 22903 www.timmons.com RE: Charlottesville Albemarle SPCA — VSMP Permit Plan Review — WP0201800030 - Comment Response Letter Dear WW Associates: We have reviewed all of your comments from August 3, 2018 and made the necessary revisions. Please find our responses to the comments below in bold lettering. 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. Please add WP0201800030 to the cover sheet of the SWPPP, plans, and stormwater management calculations package. Revision I Response: WPO# has been added to Plans, SWPPP, and Calculations. Revision I Comment: Comment addressed. 2. SWPPP Section I — Please provide a registration statement that is completed to include the certification. Please delete instruction for completing the registration statement. Revision I Response: Registration statement has been sent to the owner for signature. We acknowledge that a signed registration statement is needed for the SWPPP prior to plan approval. Revision I Comment: Acknowledged. 3. SWPPP Section 2 — Please provide a copy of the DEQ coverage letter when obtained. Revision I Response: DEQ coverage letter will be added when obtained. Revision I Comment: Acknowledged. 4. SWPPP Section 7 — Impaired water status cannot be verified as registration statement is not completed. Revision I Response: Acknowledged. CIVIL ENGINEERING I ENVIRONMENTAL I SURVEYING I GIs I LANDSCAPE ARCHITECTURE I CONSTRUCTION SERVICES Revision I Comment: Comment not addressed. The discharge is to DEQ identified impaired waters. Please include the verbiage contained in 9VAC25-880-70(B)(4)(b) and (c) and (13)(4)(d)(1) and (2). SWPPP has been revised to include the requested verbiage. S. SWPPP Section 8 — Please provide the information requested. Revision I Response: Qualified personnel shall be provided once a contractor has been selected. Revision I Comment: Acknowledged. 6. SWPPP Section 9 — Please complete and sign the certification. Revision I Response: Certification has been sent to the owner for signature. We acknowledged that a signed certification is needed for the SWPPP prior to plan approval. Revision I Comment: Acknowledged. 7. SWPPP Section 10 — Per 9VAC25-880-70 Part K, please provide the person with the authority to sign inspection reports or to modify the stormwater pollution prevention plan. Revision I Response: This information will be provided once a contractor has been selected. Revision I Comment: Acknowledged. 8. Please note that additional comments may be generated based on responses to these comments. Revision I Response: Acknowledged. Revision I Comment: Acknowledged. B. Pollution Prevention Plan (PPP) The PPP content requirements can be found in County Code section 17-404. 1. SWPPP Section 6 PPP meets Albemarle County Code section 17-404. Revision I Response: Acknowledged. Revision I Comment: PPP approved. C. Stormwater Management Plan (SWMP) VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This plan is disapproved, and the reasons are provided in the comments below. The stormwater management plan content requirements can be found in County Code section 17- 403. 1. Please provide Owner's phone number and email address for the Owner to receive correspondence. Revision I Response: This information has been added to the cover sheet. Revision I Comment: Comment addressed. 2. Please provide closed conduit storm drain pipe and drop inlet or curb drop inlet calculations using VDOT LD229 and LD204 worksheets (see VDOT Drainage Manual and Section 6 Drainage Systems of the Albemarle County Design Standards Manual). Revision I Response: Albemarle County design standards manual calls for stormwater calculations to be presented in a tabular format. We feel that the calculations as presented provide the pertinent information for the pipe/inlet design. Revision I Comment: Comment not addressed. The Albemarle County VSMP/ESC Program Authority Administrator requires submission of inlet computations on VDOT Form LD204 and storm drain on VDOT Form LD209 or a similar form that includes all the information presented on the sited VDOT forms to include the required storm event(s) (inlets throats 4"/hour and I0-year check storm and pipe system at the I 0-year storm). Forms LD204 and LD209 have been provided with this submission. See Calculations book. 3. The drainage area divides on the Phase 2 USC plan does not address where roof runoff from the existing building and the northern most and southern most new building additions enters the closed conduit storm drain system. It appears that roof drainage is directed to existing structure "A". Please provide closed conduit storm drain calculations from existing structure "A" to existing structure "G" and reroute the existing underground detention system. Revision I Response: Roof drainage drains to structure "A". See Sheets C6.2 and C5.1. Revision I Comment: Comment addressed. 4. It appears that structures "C" and "2F" are stormceptors and appears to be of the inlet type. It appears that an OSR model is proposed as based on Figure 3 presented in the design calculation booklet. Please provide sizing calculations and Stormceptor Model No. to demonstrate that proper size unit is being provided as based on the flow directed to the unit. Also, provide the proper inlet/outlet drop per the stormceptor technical data sheet for the selected unit (or denote custom design). Revision I Response: Stormceptor sizing information as well as details have been added to Sheet C5.1. Revision I Comment: Comment addressed. S. Please provide the numeric identifier on each underground detention facility to match that indicated in the Model Schematic (Figure 4 of the design calculation booklet) and show on plan sheet (C4.2) and detail sheet (C5.1). Revision I Response: Detention facilities have been numbered to match the calculations. See Sheet C4.2. Revision I Comment: Comment addressed. 6. Please provide soil group and soil surface description to facilitate verification of weighted CN for each subbasin's input data in the design calculation booklet. Revision I Response: This information has been added to the calculations book. Revision I Comment: Comment addressed as based on item 2 of the storm sewer computation notes on Sheet C5. I and the response to Comment 10 below states the entire site is within hydrologic soil group B. Acknowledged. 7. Please provide stage discharge curves and routings of I and 10-year storm events for New Det 01 and New Det 02. Revision I Response: This information has been added to the calculations book. Revision I Comment: Comment does not appear to be addressed. The requested information was not observed in calculation package. Please provide requested information. Requested information is now shown in the calculations package. 8. Please provide the name of the DEQ certified facility that is intended to provide nutrient credits. Provide VAHUC for the project site and for the nutrient credit facility. Revision I Response: This information has been provided with this submission. Revision I Comment: Comment addressed. 9. It appears that the existing underground detention upstream to the existing bioretention facilities is modeled with a Tc of 5 minutes. Please provide calculations demonstrating a Tc of 5 minutes. Revision I Response: Water is conveyed to the existing detention facility via the onsite storm system. This area is primarily asphalt and has a low time of concentration therefore the minimum allowable Tc was used. Revision I Comment: Comment addressed. 10. Please correct the VRRM site summary as per sheet No. C5.3 denotes a portion of the site is in hydrologic soil group B Glenelg and a portion is within hydrologic soil group C Elioak. Revision I Response: The plan sheet shown on C5.3 is from an older plan and is provided for reference only. Current soils information is shown on Sheet C6.1, which shows that the entire site is within soil group B. Revision I Comment: Comment not addressed. No soils information is shown on Sheet C6.1 as stated. Please turn on the soils layer to include soils boundary and soils designation and add to the legend. Soils information is shown on Sheet C6.1, legend has also been revised. 11. Please note that additional comments may be generated based on responses to these comments. Revision I Response: Acknowledged. Revision I Comment: Please note that additional comments may be generated based on responses to these comments. Acknowledged. D. Erosion and Sediment Control Plan (ESCP) Virginia Code 62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan is disapproved, and the reasons are provided in the comments below. The erosion control plan content requirements can be found in County Code section 17-402. 1. The County's Critical Resources Plan denotes managed critical slopes throughout the parcel. Please denote the location of the managed slopes with a symbol and add to the legend. Revision I Response: Critical slopes have been added to Sheets C6.0 and C6.1. Revision I Comment: Comment addressed. 2. Please provide a top of wall spot elevation at the northeast corner of the eastern most new parking lot to verify that retaining wall height is not greater than six feet as it appears that the retaining wall is located within a managed critical slope area. Revision I Response: A spot has been shown in the requested area. See Sheet C3.1. Revision I Comment: As based on the elevations given, the height of the retaining wall north of the terminus of the northern most new parking area exceeds 6 feet and is within the managed steep slope overlay district. Either reduce the wall height to under 6 feet or provide a double tiered wall system. Retaining wall height has been reduced. See Sheet C3.1. 3. Please address pedestrian access as it is noted that Phase I and Phase 2 CE will conflict with sidewalk to remain. Revision I Response: A portion of the sidewalk where the CE is shown is to be removed as a part of this project. A note has been added to Sheet C6.2 stating that the contractor is responsible for maintenance of traffic (including pedestrian) during construction. Revision I Comment: Comment addressed. 4. Please add dust control symbol to the E&SC plan sheets legend and add locations to the plan. Provide same information for temporary and permanent seeding as well. Revision I Response: This information has been added to the plans. See Sheets C6.0 and C6.1. Revision I Comment: Comment addressed. S. A DID is shown in a portion of the area to be filled to construct a new parking lot (eastern most new parking area). Please explain the DID status during earthwork operations. Revision I Response: The DID shall remain in place and be adjusted by the contractor during earthwork operations. Revision I Comment: Please note that the Albemarle County VSMP/ESC Authority Administrator does not permit the placement of erosion and sediment control measures in the way of grading during construction (see attached Engineering E&SC Plan Checklist. Item circled on Sheet 3 of 4. Please provide E&SC controls for this area that do not conflict with grading operations. ESC plans have been revised to remove 6. Please add soil boundary to the Phase 2 E&SC plan sheet. Revision I Response: Soil boundaries have been added to the plans. See Sheet C6.1. Revision I Comment: See Part C Revision I Comment 10. Please provide the requested information. xxXc 7. Please provide a stockpile and contractor's staging/laydown and parking areas to the E&SC plan sheet. Revision I Response: This information has been added to the plans. See Sheet C6.0. Revision I Comment: Comment addressed. 8. Please verify that cut or fill balances do not exceed a 10,000 cubic yard deficit. If deficit is exceeded, an approved waste area will need to be identified. Revision I Response: Cut/fill balances for the project are less than 300 cubic yards. Revision I Comment: Comment addressed. 9. SSF is shown crossing contours at several locations on the Phase I and Phase 2 E&SC plan. SSF is to run parallel with contours. Please place SSF on tangents or provide other perimeter E&SC measures. Revision I Response: SSF locations have been revised. See Sheets C6.0 and C6.1. Revision I Comment: Comment not addressed. Please adjust super silt fence as requested. Silt fence locations have been revised. 10. It appears that slopes sleeper than 3:1 are proposed on the south side of the eastern most new parking lot and the north side of the northern most new parking lot. Please provide a symbol for slopes steeper than 3:1 and add to the legend and to the E&SC plan sheets. These areas are to have low maintenance (not grass) ground cover specified (what type) on the E&SC plan sheets. Revision I Response: This information has been added to Sheet C6.1. Revision I Comment: Comment not addressed. The criterion is for slopes steeper than 3:1. Then Consultant has referenced 2:1 slopes. Please correct plan to address comments. Note has been revised to state 3:1. 11. Please provide an alpha or numeric indicator for the two excavated drop inlet traps to facilitate reference. Provide a stage/storage volume table for each trap and identify the wet and dry storage volumes and elevations, and a calculation verifying a 2:1 length/width ratio for flow path in consideration of the inflow location. Revision I Response: This information has been added to Sheet C6.0. Revision I Comment: Comment addressed. 12. The clean water DID on the west side of the project site is to discharge to a stable/stabilized outfall. Please provide appropriate drainage area/flow calculations and size riprap apron or other measures to stabilize outfall. Revision I Response: A temporary level spreader has been added at the end of the CWD. See Sheet C6.0. Revision I Comment: Comment addressed. 13. Please add the drainage area (0.30 acres) to the volume calculation for the eastern most drop inlet sediment trap on Sheet No. C6.0. Revision I Response: Calculation has been revised to include 0.30 acres. Revision I Comment: Comment addressed. We have included PDF copies of the plans and calculations for your review. If you have any questions or comments, please feel free to give me a call at 434.295.5624. Sincerely, John Wilson, PE Project Engineer