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Home My WebLink AboutSW3191204_Responce to Comments_20200515BOHLER// Bohler Engineering NC, PLLC 1927 South Tryon Street, Suite 310 Charlotte, NC 28203 980.272.3400 April 23, 2020 NCDEQ 610 East Center Avenue Suite 301 Mooresville, NC 28115 Re: Comment Response Letter Arka Heights 4610 Old Charlotte Highway Monroe, NC 28110 BE # NCC182110 Bohler Engineering is pleased to submit on behalf of Liquid Management, LLC the revised Construction Documents for the above -named project. The following is our comment response letter addressing comments received from Jim Farkas dated April 15, 2020. Each comment is addressed and responded to as follows: NCDEQ Submission Letter Response - Comment 1: Original Comment 4f — "Please include the existing BUA." Based on the information shown in the Application, there are 15,816 sf (10,333 sf + 5,483 sf) of existing BUA located on site in existing conditions. In proposed conditions, there will be 267,401 sf (133,961 sf + 109,625 sf + 15,265 sf + 8,550 sf) of BUA in proposed conditions. This results in a net increase of 251,585 sf of BUA. The drainage area to the proposed SCM only contains 243,586 sf (133,961 sf + 109,625 sf) of BUA. Per 15A NCAC 02H .1002(43) and 15A NCAC 02H .1003(3)(b), in order to meet the runoff -treatment method, at least the net increase in built -upon area must be treated in the SCM(s). Please ensure that the existing built - upon area is correctly shown. In order to eliminate some confusion, BUA tables can be added to sheets C-405 & C-406. Response 1: Existing BUA listed on the Stormwater Application is BUA to remain. Total existing BUA for the site is 37,348 sf. Total proposed (267,401) — Total BUA draining to Wet Pond (243,586) _ 23,815 sf < Existing BUA (37,348) Comment 2: Original Comment 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, 8m)." Please indicate where this note was placed in the plan set (I could not find it, but I may have overlooked it). Response 2: Note added that to sealed engineered drawings that no wetlands exist on site on sheet C-401, Note 5. Comment 3: Original Comment 8 — "Since the wet ponds are connected via a 0% slope equalizing pipe and wet pond 2 does not have an outlet/riser structure, the two wet ponds should be treated as a single wet pond in the Application and supporting documents..." Please correct the following issues: a. Application: i. Section IV, 9 — This project should only have one drainage area since there is only one proposed SCM. Revised as requested ii. Section IV, 10 — Portions of the site that do not drain to the proposed SCM (Drainage areas 3 & 4) do not need to be included in this table. Generally, since there is only one SCM, there would only be one drainage area column, but due to the nature of this facility, including the "east' and "west' drainage areas is acceptable. Revised as requested b. Calculations: i. Ensure that the proposed wet pond meets all sizing MDCs (It appears that the design meets all of the sizing requirements, you just needs to show that the entire wet pond (not just the east and west portions individually) meets the MDCs). MDC breakdown for entire pond provided in calculation package after stage storage tables Response 3: See responses in red above Comment Response Letter HLER Charlotte Heights, LLC 4610 Old Charlotte Highway BE # NCC182110 April 23, 2020 Page 2 of 3 Comment 4: Original Comment 9cii — "Runoff from the forebay to STM B-EP short circuits the wet pond (Wet Pond MDC 4). Please revise the design to avoid this." Please provide a detail for the proposed permanent baffle. Response 4: Detail provided on sheet C-404 Comment 5: Original Comment 10b — "The percent impervious area for the drainage area to wet pond 1 is shown as 63% in the Supplement-EZ Form, 70% in the Application, and 80% in the calculations." The percent impervious area for the drainage area to the wet pond is shown as 60% in the Supplement-EZ Form, 62.5% in the Application ((133,961 sf + 109,625 sf)/(222,329 sf + 167,250 sf)), 62.5% in the calculations ((5.11 ac 60% + 3.84 ac " 66%)/(5.11 ac + 3.84 ac)=62.5%), and 70.6% in the HydroCAD printout ((5.11 ac 66.54% + 3.84 ac " 76.04%)/(5.11 ac + 3.84 ac)=70.6%). Please revise for consistency. Response 5: After examining the program input, HydroCAD includes the water surface area of the ponds in its impervious percentage thus giving a higher built upon area than in the other forms. Removing the water surface area would correct the impervious percentage output but would produce inaccurate results therefore the BUA output remains slightly higher than proposed. Supplement EZ form, Applications, and other calculations have been revised to all match. Comment 6: It is recommended that the latest version of the Supplement-EZ Form be completed and submitted. This file can be found at the following link: https:Hdeg.nc.gov/about/divisions/energv-mineral-land- resources/energv-mineral-Iandpermit-quidance/stormwater-bmp-manual Response 6: Noted, thank you. Supplement-EZ form will be updated for next project. We would prefer to continue with this version on this project and address comments below. Comment 7: If the updated Supplement-EZ Form will not be used, please correct the following issues with the provided Supplement-EZ Form: a. Proposed new BUA/Total BUA — Please include the 10,030 sf of future BUA into this value. a. Corrected b. Percent BUA of drainage area — Recalculate this value taking the prior comment into consideration. a. Corrected, please note the NCDEQ spreadsheet rounds the value of 62.5% to 63% c. Surface area of the main permanent pool — This value (19,609 sf) does not match the value from the provided stage -storage table (6,476 sf + 8,936 sf = 15,412 sf). Please revise for consistency. a. Corrected d. Volume of the main permanent pool — This value (52,038 cf) does not match the value from the provided stage -storage table (52,117 cf). Please revise for consistency. a. Corrected e. Elevation of the bottom of the permanent pool - When entering information into the form that is different for the east and west portions of the pond, you should put a note in the note box explaining this and showing both values. a. Corrected f. Volume of the forebay — This value (8,110 cf) does not match the value from the provided stage -storage table (8,479 cf). Please revise for consistency. a. Corrected g. Depth of the forebay at entrance/exit — The provided cross -sections in the plans do not show this elevation change from the entrance to the exit. Please revise the plans to show this. Also, ensure that at least six inches of sediment storage are provided for both the entrance and exit of the forebay. a. Corrected h. Clean -out depth for forebay — The cleanout depth is the distance from the permanent pool surface elevation to the top of he sediment storage elevation. a. Corrected i. Drawdown time for the temporary pool — This value (92.16 hrs = 3.84 days) does not match the value from the provided in the calculations (3.98 days). Please revise for consistency. a. Corrected Response 7: Responses in red above. Comment Response Letter HLER Charlotte Heights, LLC 4610 Old Charlotte Highway BE # NCC182110 April 23, 2020 Page 3 of 3 Comment 8: The Total Impervious Surface Area for Drainage Area 1 should be a summation of all of the proposed BUA (On -site and Future) listed in the Drainage Area 1 column of the table in Section IV, 10. Response 8: Corrected Comment 9: NOTE: Per Division policy, the next review of this application will be the final review. Failure to provide the requested information will result in the project being returned as incomplete. The return of a project will necessitate resubmittal of all required items, including the application fee. Response 9: Noted, thank you. Comment 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:Hedocs.deq.nc.gov/Forms/SW_Project_Submittal Response 10: Requested materials attached and uploaded Should you have any questions regarding this project or require additional information, please do not hesitate to contact me at (980) 272-3400. Sincerely, BOHLER Steve Farmartino, P.E. Project Manager