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HomeMy WebLinkAboutSW3240302_Response To Comments_20240307 LandDesign CREATING PLACES THAT MATTER. February 23, 2024 Jim Farkas Environmental Engineer North Carolina Department of Environmental Quality Division of Energy, Mineral, & Land Resources—Stormwater Program 512 N. Salisbury Street 1612 Mail Service Center Raleigh, NC 27699-1612 RE: Preserve at Forest Creek Phase 2 Stormwater Permit No. SW3220702 Dear Mr. Jim Farkas, 1. Original Comment 8(Prior Comment 1)—There still appears to be issues with the BUA accounting for this project.A permit cannot be issued for a site without an accurate accounting of all of the proposed BUA.An accurate BUA accounting is also required to verify that the project is meeting treatment requirements. a. Per the provided Deed Restriction Form (NOTE: The provided hard copy of this form was missing the cover page),the total amount of BUA allocated to the individual lots is 1,329,021 sf(see attached). Per the Supplement-EZ Form,the total amount of BUA allocated to the individual lots is 1,328,993 sf(Entire Site Column, Line 9).These values should match. LDI Response: This was a rounding error through Excel. BUA deed restriction application and Supplement EZ form have been revised to match. b. Please ensure that all of the BUA within the project area, not just the BUA draining to the proposed SCMs, is accounted for in the Entire Site Column of the Drainage Area Page of the Supplement-EZ Form. For example,the BUA associated with the proposed asphalt trails does not appear to be included in this column. If it is not possible to capture and treat the net increase in BUA for this project(required to meet Runoff Treatment), the portions of the project area that are not captured by an SCM can be considered as a low-density area(with Division approval per 15A NCAC 02H .1003(1)(d)). LDI Response: The proposed asphalt trails are not included in this as they are place holders for the Town of Waxhaw to determine routing of trails. Would the trails be able to be considered low-density since they don't drain to any SCM and most are in the floodway? For now, the BUA for the trails has been added to the Supplement EZ form under Future BUA for the total site. c. Please ensure that the Total Drainage Area for the entire site column is equal to the project area (the entire site column is not necessarily a sum of all of the other columns, but rather an accounting of the entire site/project area. The project area is shown as 105.26 ac in the Application (Section IV, 7)and as 3,698,571 sf(84.91 ac) in the Supplement-EZ Form (Drainage Areas Page, Entire Site Column, Line 5). LDI Response: Total Drainage Area is equal to the project area. LANDDESIGN.COM 2. Prior Comment 3.b.—Please ensure that the percent BUA values for the drainage areas as shown in the Application are correct and correspond to the calculated values. For example,for Wet Pond 7,the shown value, 71.00%does not correspond to the percent BUA calculated for the drainage area (438,641 sf/620,017 sf=70.75%0 71.00%).This appears to be an issue of precision. LDI Response: This is correct in the sense that it is a precision of rounding but based on NCDEQ's Supplement EZ form line 18 of the Drainage areas tab, it automatically rounds up to the nearest whole number.This document is locked by NCDEQ, and I cannot modify it to go to 2 decimal places. For now, until the form is revised, the data has been modified on the PDF. 3. Wet Pond 8—The drawdown orifice diameter for this wet pond is shown as 2.5"in the Supplement-EZ Form and cross-sectional view of the SCM and is shown as 3.0"in the calculations and detail view of the outlet structure. LDI Response: This has been revised on the supplement-EZ form. 4. Wet Pond 10—This SCM includes a retaining wall, but Line 6 of the Wet Pond Page of the Supplement- EZ form indicates that there are no retaining walls. LDI Response: This has been revised on the supplement-EZ form. 5. Wet Pond 10—The average depth calculation for this wet pond appears to be incorrect. LDI Response: This has been revised on the supplement-EZ form. Please note that this was the fourth review in a year and half from when these were originally submitted. It is understandable that there were staffing shortages, and a backlog of review times was the result of this but these comments above were very minor and could have been responded to and corrected within a weeks' time if there were better review times and/or communication with designers and reviewers. Sincerely, David Gusty, PE on behalf of Frank McMahan, PE LandDesign, Inc.