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Home My WebLink AboutSW4191201_17-116 - Comment Responses_3/26/2020CLH design, p.a. CLH design, p.a.CLH design, p.a.CLH design, p.a.CLH design, p.a. 400 Regency Forest Drive, Suite 120 Cary, North Carolina 27518 P: 919.319.6716 www.clhdesignpa.com Site Plan Comment Responses Date: March 26, 2020 Re: Lewisville Middle School- Forsyth County - State Project SW4191201 Dear Jim Farkas : Below in red are our responses to the 2nd round of review comments received for the above referenced project. Division of Energy, Mineral and Land Resources Comment 1: 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).” What sheet was this note added to? I’m having a hard time finding it. Response: This has been added to the notes section of all sheets. See any plan sheets. Comment 2: Original Comment 6 – “Please provide a stage-storage table for the main pool and forebay sections of the proposed wet pond so that the pond sizing calculations may be verified.” The provided stage-storage table for the main pool incorrectly calculates the volume of the main pool as 97,754 cf. Please ensure that the provided stage storage table corresponds to the volumes shown in the calculations and used on the Supplement-EZ Form. Response: Stage storage has been revised in our model. There should be a 0.2% difference seen between model and calculations. See new calculations booklet. Comment 3: Original Comment 7 – “Please provide a stage storage table for the portion of the stormwater wetland that is above the permutant pool elevation so that the drawdown calculations can be verified.” The provided stage storage table for the temporary storage in the stormwater wetland incorrectly shows the permanent pool elevation (Stage 0.0) at elevation 812.50 ft. Please revise for consistency with the plans, calculations, and Supplement-EZ Form. Response: There was a typo in the model with the elevation. This has since been revised which matches with the Supplement-EZ , calculations, and plans. See revised calculations booklet. Comment 4: Original Comment 10 – “Please address the following on the Supplement-EZ Form:” a. Drainage Areas Sheet Line 7 – “This item is the net increase in BUA (post-construction BUA – pre-construction BUA) for either the entire site or the drainage area to the proposed SCM.” Site Plan Comments March 26, 2020 CLH design, p.a. 1. Entire Site – Post-construction BUA = 382,098 sf (Sheet C03.08). Pre-Construction BUA = 30,890 sf (Sheet C03.07). The New BUA for the entire site is the difference between these two. Response: Line 7 has been revised to be the difference (382098 – 30890 = 351208) 2. DA 1 – Post-construction BUA = 349,119 sf (Sheet C03.08). PreConstruction BUA = 23,164 sf (Sheet C03.07). The New BUA for this drainage area is the difference between these two. Response: Line has been revised to be the difference (349119-23164=325955) 3. DA 2 – Post-construction BUA = 32,979 sf (Sheet C03.08). PreConstruction BUA = 300 sf (Sheet C03.07). The New BUA for this drainage area is the difference between these two. Response: Line has been revised to be the difference (32979-300=32679) Line 10 – “This item is the net increase in BUA (post-construction BUA – pre-construction BUA) for either the entire site or the drainage area to the proposed SCM, broken down by type.” 1. Use the same methodology as described for Line 7 but broken down by each type of BUA for the Entire Site, DA 1, & DA 2. The items of Line 10 should add up to Line 7. Response: New BUA has been revised per instructions given. The only difference should be seen in roof area and other BUA as other types of BUA were not present in pre development conditions. Line 13 – “This item is equal to the lesser of the post-construction BUA or the pre-construction BUA (for either the entire site or the drainage area to the proposed SCM). For this project, Line 13 + Line 7 = Line 5.” 1. Entire Site – Post-construction BUA = 382,098 sf (Sheet C03.08). Pre-Construction BUA = 30,890 sf (Sheet C03.07). PreConstruction BUA is less than Post-Construction BUA so this value should be used Response: Line 13 has been revised. 2. DA 1 – Post-construction BUA = 349,119 sf (Sheet C03.08). PreConstruction BUA = 23,164 sf (Sheet C03.07). Pre-Construction BUA is less than Post-Construction BUA so this value should be used. Response: Line 13 has been revised. 3. DA 2 – Post-construction BUA = 32,979 sf (Sheet C03.08). PreConstruction BUA = 300 sf (Sheet C03.07). Pre-Construction BUA is less than Post-Construction BUA so this value should be used. Response: Line 13 has been revised. Line 15 – “This item is the net decrease in the BUA from pre-construction to post-construction, if applicable. For this project, Line 13 + Line 15 = Pre-construction BUA.” 1. Line 15 – “This item is the net decrease in the BUA from pre-construction to post- construction, if applicable. For this project, Line 13 + Line 15 = Pre-construction BUA.” Site Plan Comments March 26, 2020 CLH design, p.a. Response: This line has been revised for all drainage areas to be the net decrease. Since the post development is larger than pre, there is no net decrease. Line 19 – “The design volumes should be calculated using either the Simple Method or the Discrete NRCS Curve Number Method (Refer to the Stormwater Design Manual, Part B).” 1. DA 1 – The HTR method is used to size the pond, not the design volume. Response: This line has been revised to indicate simple method for the design volume. Simple for wetlands. b. Wet Pond Sheet Line 44 – “The forebay exit must be shallower than the forebay entrance (Wet Pond MDC 5).” 1. Please update the plans to reflect this. NOTE: Per Wet Pond MDC 3, the forebay (At both the entrance and exit) must have at least 6 inches of sediment storage depth. Response: Currently the plans indicate a more gradual slope on the forebay exit versus the forebay entrance, which in turn provides a smaller depth at the exit of the forebay – these are 2 foot countours. Additional notes have been added to ensure this concept is clear. c. Stormwater Wetland Sheet Line 28 – “The forebay exit must be shallower than the forebay entrance (Stormwater Wetland MDC 6).” 1. Please correct this or Line 27. Response: Line 28 has been revised to be 6” shallower than deepest point. The forebay is so small that there is not much room to adjust. Additional notes have been added to make sure clear. Line 49 – “Soil amendments must be done to a depth of 12 inches, if required (Stormwater Wetland MDC 4).” 1. Please correct this. Response: The supplement-EZ form has been revised to 12” depth. Comment 5: Supplement-EZ, Wet Pond Sheet, Line 34 – The cleanout depth of the forebay is the distance from the permanent pool elevation to the top of the sediment storage area. Please revise. Response: The cleanout depth has been revised to be distance from permanent pool elevation 826.5 – top of storage area (822) = 4.5’ or 54”. See new supplement-EZ form. Comment 6: Supplement-EZ, Stormwater Wetland, Line 52 – Please provide this number. Response: This has been added in by hand. For your awareness, the Supplemental EZ form gives an error message regardless of the number being appropriate for the MDC “This value doesn’t match the data validation restrictions defined for this cell.” Comment 7: Please ensure that the quantities of plans shown on sheet C07.06 add up properly. Site Plan Comments March 26, 2020 CLH design, p.a. Response: The plant numbers have been revised. 113 plants should have been shown for the Tussock Sedge. This has been revised. Comment 8: Please provide a signed & sealed, original, revised copy of the Supplement-EZ Form. Please ensure that the form is printed at a scale that does not cut off any portion of the form. Response: The revised Supplement-EZ form will be a up to date original copy of this form. 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: 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://edocs.deq.nc.gov/Forms/SW_Project_Submittal Response: With this submittal please find 2 hard copies of the revised plan sheets and 1 hard copy of other documents. PDFs have been uploaded online as well. While it is not required, it is recommended that the off-site drainage from upstream properties be diverted around the SCM since the applicant cannot maintain control over the development of property that they do not own Response: Noted. End of Responses Thank you for all your help and please call with any questions. Sincerely, For CLH design, p.a. Renee Pfeifer, PLA Vice President