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HomeMy WebLinkAboutSW6191005_Response to Comments_20191218(3 Stantet SW6191005 Response To Request for Additional Information 12/18/2019 Please verify that the provided latitude and longitude are correct (Section I, 4). It appears that the project is about a half of a mile away from the provided coordinates. Response: The coordinates have been revised to indicate the actual project location and not the entrance to the compound (previously reported). 2. Please change the applicant/organization to "Director of Public Works (DPW)" (Section III, 1, a). Response: Application has been updated. 3. Please use the project area of 2.25 acres for the total property area, total project area, and percent impervious area calculation (Section IV, 4, 7, & 8). Including the existing BUA that will be replaced 1:1 with proposed BUA and the disturbed pervious areas will not impact State stormwater quality requirements for this project. Response: The project areas has been revised to match the LOD of 2.25 acres. 4. Please dimension the proposed BUA so that the provided values may be verified (Section VI, 8, j). Response: The CS sheets have been included in this resubmittal and have dimensions or areas stated on the plan. SWM101 also includes stated areas. Sidewalks widths are dimensioned or stated in the general note on the CS sheets. 5. Please delineate the wetlands on the plans or provide a note stating that no wetlands exist. Provide documentation of the qualifications and identity of the individual who made this determination (Section VI, 8, m). Response: No wetlands exist on site as determined by Erich Hoffman of DPW - Environmental Section. This note has been added on SWM101. ® Sta ntec SW6191005 Response To Request for Additional Information 12/18/2019 6. There is an existing stormwater permit, SW6110105, that was applied for when the dining addition, gym addition, and CDD/signal addition were added to this building. There appears to be some overlap between the area covered under that permit, and the area that will be covered under this permit, specifically where the new building addition is being proposed. Please show the SCMs associated with SW6110105 and their drainage areas on the plans. If these facilities are being impacted by the proposed development, the loss of treatment must be made up for by the proposed SCMs (Section VI, 8, n). Response: The plans for this permit were obtained and the drainage areas as well as the facility were placed on the plan and are now accounted for in the supplemental forms, plans, and calculations. There is no loss in treated/permitted areas. 7. Please provide some form of pretreatment for the stormwater bypassing the grass swales that enters infiltration facilities 2 & 3 (Infiltration MDC 4). Response: A pea gravel verge has been added to the infiltration basin detail on C-505 and on the plan view CG104. 8. Please provide cross -sections of the proposed infiltration systems in accordance with H15 NCAC 02H .1042(2)(h). Response: Cross sections of each facility haven been added to SWMI01 in addition to the detail cross section on C-505. 9. Please make the following corrections to the Supplement-EZ Form: a. Cover Page Sheet i. Line 2 — See prior comment. Response: Change made to 2.25 Ac. b. Drainage Areas Sheet i. Entire Site Column Line 5 — This is the total amount of BUA that will be present, post- construction, within the project area. Since there are no subdivided lots, this value should equal Line 7 of this column. Response: This has been change to account for existing BUA in the project area (840 SF) as well as new BUA (34,998 SF). Since Line 7 is new BUA only, it is 804 SF less than Line 5. ® Sta ntec SW6191005 Response To Request for Additional Information 12/18/2019 2. Line 7 —This is the new (net increase) in BUA that will be placed within the project area. This value should be equal to the sum of the items in Line 10 of this column. Response: This has been revised and now matches Line 7. 3. Lines 8 & 9 — Since this column is an accounting of everything within the project area, there should not be any off -site areas. Response: This has been revised and does not include offsite areas for the "Entire Site" column. 4. Line 13 — Any impervious area that will remain post -construction, like the Dumpster pad, should go on this line. Response: The dumpster pad (3,988 SF) has been included as well as some miscellaneous existing B UA areas in the utility LOD (251 SF). Drainage Area I Treats off -site existing BUA to remain as well as previously treated and permitted offsite roof BUA now delineated on SWMI01. This has been added to the columns for DA 1. ii. Infiltration Basin Columns Line 5 — This is the total amount of BUA that will be present, post- construction, within the drainage area to each facility. Since there are no subdivided lots, this value should equal Line 7 plus Line 9. Response: The total amount of BUA in Drainage Area column one has been revised to reflect the total BUA of 26,455 SF. Breakdown as follows: Line 7 updated for new BUA only (12,196 SF). Lines 8 and 9 are equal since all offsite area is also BUA (13,419 SF), however, Line 9 + Line 7 does not equal Line 5 because there is existing on -site BUA of 840 SF. This BUA was already permitted and therefore is nested under Line 14 which equals the existing permitted off -site BUA of 4,200 SF + the existing permitted on -site BUA (to be replaced) of 840 SF. Line 9 reflects the 4,200 SF existing permitted BUA + Line 13. Line 14 + Line 13 represents all offsite and onsite BUA in the drainage areas and therefore Line 13 + Line 14 + Line 7 = Line 5. ® Sta ntec SW6191005 Response To Request for Additional Information 12/18/2019 2. Line 7 — This is the new (net increase) in BUA that will be placed within the drainage area to each facility and also within the project area. This value should be equal to the sum of the items in Line 10. Response: The columns have been revised accordingly. iii. General 1. Do not use the actual volumes that can be stored in the facilities on the Infiltration System Sheet, use the values from Line 18. Response: Design volumes from Line 18 are now used. c. Infiltration System Sheet i. Line 2 — See prior comment. Response: Design volumes from Line 18, Drainage Areas, are now used ii. Line 16 — Answer this item. Response: Item has been answered iii. Line 44 — See prior comment. Response: Design volumes from Line 18, Drainage Areas, are now used. iv. Line 45 — Recalculate these values using the design volume, not the volume that can be held in the facilities. Response: Calculations have been updated using the design volumes. 10. Provide pdfs of all revisions, 2 hardcopies of revised plan sheets, and 1 hardcopy of other documents. Pdfs must be uploaded using the form at: https://edocs.deq.nc.gov/Forms/SW Project Submittal Response: Please see attached submittal.