The URL can be used to link to this page

Home My WebLink AboutSW5210202_NCDEQ Stormwater 3rd Comment Responses_20210510 5410 Trinity Road P 919.866.4951 Suite 102 F 919.859.5663 Raleigh, NC 27607 www.timmons.com May 5, 2021 NCDEQ STORMWATER COMMENT RESPONSES RE: Project Name: Franklin Co. E911 Project ID: SW5210202 County: Franklin Town: Louisburg Address: 285 T Kemp Road Submitted By: Timmons Group Date Received: May 5, 2021 Plan Type: Institutional Please see comments in response to the Checklist of Additional Items below provided by Jim Farkas, Environmental Engineer, Stormwater Program. CHECKLIST OF ADDITIONAL ITEMS The Division of Energy, Mineral and Land Resources (DEMLR), received a Stormwater Management Permit Application for the subject project on April 5, 2021. A review of that information has determined that the application is not complete. The following information is needed to continue the stormwater review: 1. Prior Comment 8 ase dimension the project boundary with bearings and Please show the entire extents of the project boundary (You may wish to add this information to plan sheet C4.4). The project boundary has been labeled with bearing and distances on Sheet C4.4. 2. Prior Comment 16a e electronic files for this submission. Please ensure that the files from the April 5 the submission and the files for the next submission get uploaded. Occasionally, the file upload portal will stall (and not register the upload) if the files are very large. The files have been uploaded online. 3. There appears to be a discrepancy between the BUA information shown in the Application/Supplement-EZ Form and as shown in the SIA calculations. In the Application/Supplement-EZ Form, the drainage area to the wet pond is shown as 1.49 acres (64,812 sf) and the amount of BUA in the drainage area is shown as 0.60 acres (25,934 sf). The SIA calculations show the drainage area to the wet pond as 1.48 acres and the amount of BUA in the drainage area as 0.56 acres. Make sure that you are not double counting Existing BUA. The Application/Supplement EZ Form was originally correct, the SIA calculations have bee updated to 1.49 acres with 0.60 acres of impervious. CIVIL ENGINEERING | ENVIRONMENTAL | SURVEYING | GIS | LANDSCAPE ARCHITECTURE | CONSTRUCTION SERVICES 5410 Trinity Road P 919.866.4951 Suite 102 F 919.859.5663 Raleigh, NC 27607 www.timmons.com 4. The forebay volume appears to be incorrectly calculated in the SIA calculations. The forebay (the stage-storage table shows an incremental volume of 106 cf from elevation The spreadsheet has been updated to not include the incremental volume between 245- 246.The pond became 1 foot deeper to reach a sufficient average depth. 5. The provided stage-storage table for the main pool and forebay do not show the cross- sectional was also mentioned in Prior Comment 12. Since the berm separating the forebay from the main pool is below the permanent pool elevation an imaginary vertical line that runs along this berm should be used to divide the main pool from the forebay (See image below). The main pool and forebay volumes have been calculated up to the permanent pool elevation. 6. Please correct the following issues with the Supplement-EZ Form: a. Drainage Areas Page: i. Please complete the Entire Site Column. This column is an accounting of all of the BUA for the e site not required for this column. The column has been updated. b. Wet Pond Page: i. Lines 2, 26-29, 32, & 35 may need to be changed, depending on earlier comments. Updated ii. Line 34 The cleanout depth of the forebay is the distance from the permanent pool elevation e Updated iii. Lines 43 & 44 The depth of the forebay is the distance from the permanent pool elevation designed to have a sump near the inlet pipe (See Figure 5 of Part C-3 of the Stormwater Design Manual) in these cases, the two different depths would be recorded, but if the bottom of the forebay is at a uniform elevation, then these two Lines would be the same. Updated iv. Line 48 Per the provided detail on plan sheet C4.2, the pond draws down from below the permanent pool surface elevation. Updated These comment responses have been prepared by Brandon McLamb, Project Manager. Sincerely, Brandon McLamb, PE Project Manager Timmons Group CIVIL ENGINEERING | ENVIRONMENTAL | SURVEYING | GIS | LANDSCAPE ARCHITECTURE | CONSTRUCTION SERVICES