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Home My WebLink AboutSW4220301_Response To Comments_20220606FEI CIVIL ENGINEERS AND LAND SURVEYORS Resubmittal June 6, 2022 As designed, this project does not meet the definition of a low -density project. Per 15A NCAC 02H .1003(2)(b) low -density projects are required to be designed in a manner that maximizes dispersed flow through vegetated areas while minimizing the channelization of flow. Designing a project in a manner that maximizes dispersed flow is notably different than designing a project and then maximizing dispersed flow where convenient. There are instances where a low -density project is allowed to use piping, as outlined in 15A NCAC 02H .1003(2)(c), but these are limited to unavoidable situations. The proposed design has an excessive amount of piping to be considered as low -density. At a minimum, the following structures (and associated immediate downstream pipes) would need to be removed: GI 101, GI 102, GI 301, GI 402A, GI 405, GI 406 (NOTE: You can keep the pipe between GI 405 & GI 406 as a culvert since this is the low point of the roadway, however you cannot pipe this to the off -site bypass pipe system. FEI Response: These structures have been eliminated. The sump in Montlieu was modified such that the new storm drainage lines up with lots 19 & 20 discharge. It is recommended to reconfigure the lot lines in order to preserve/utilize the natural drainage channel on lots 9 and 19), GI 407, GI 502, YI 503, & FES 500 (The pipe network at the end of the road seems unnecessary for this project. FEI Response: The storm drainage has been reconfigured as mentioned above. The home builder will adjust swales around lot 9 to facilitate the building pad/envelope. Building lines were established based on a preliminary evaluation of septic fields and resulted in the location of lot lines. Storm drainage at the end of Montlieu has been eliminated. However, as discussed, the developer would like that to be permitted as a buildable lot; the footprint will be towards the rear of the property. A driveway culvert will need to be installed at the time of house construction when the house/driveway is built. If at some point in the future, the hammerhead turnaround is extended southward to form a roadway, a culvert can be added at that time as part of that project. For now, this area should be able to be handled via vegetated conveyance). FEI Response: Comment noted. In addition, the pipes between GI 201 & FES 200 and GI 401 & FES 400 should be shortened (reduce the pipe slopes and have the pipes daylight sooner). !!:rAFEI Civil Engineers and Land Surveyors FEI Response: Comment noted and pipe lengths have been adjusted. Note that structures have been re -numbered due to the elimination of above structures. 2. The following issues were noted with the design of the vegetated conveyances: a. The 10-year storm intensity value used (5.67 in/hr) appears to be too low for this part of the State. Please revise if needed and provide a source for the rainfall intensity value used in the calculations (it is recommended to use NOAA Atlas 14 rainfall data, available at the following address: https://hdsc.nws.noaa.gov/hdsc/pfds/Pfds_map_cont.html?bkmrk=nc). NOTE: If using a time of concentration in excess of 5 minutes to get the provided rainfall intensity value for each vegetated conveyance, please provide calculations for these times of concentration. FEI Response: Comment noted. The swale calculations have been revised/updated to a rainfall intensity of 6.88 in/hr (see NOAA rainfall intensity chart) for the 5 min 10-yr rainfall event. b. Please provide a spec for the permanent lining for the vegetated conveyances showing that the lined vegetated conveyances will remain stable for the provided flow values. FEI Response: Comment noted. Manufacturers specification for Curlex I, Curlex II and Pyramat have been submitted to follow design velocities & stresses. c. Please provide vegetated conveyances downslope of the flared end sections. These vegetated conveyances should meet the design requirements outlined in 15A NCAC 02H .1003(2)(d) since the collection systems function as curb outlet systems. FEI Response: Comment Noted. Below proposed discharge points, energy dissipators will be installed per NCDEQ Erosion Control requirements. Beyond that point, vegetative conveyances will remain. 3. The following issues were noted with the Application: a. Section IV, 10: i. "Total Drainage Area" — The Total Drainage Area of a low -density project like this one is equal to the project area (off -site drainage is not taken into account for low -density projects). FEI Response: Comment Noted. Total Drainage area has been updated to reflect only on - site area. !!:rAFEI Civil Engineers and Land Surveyors ii. "Off -site Drainage Area" - As noted above, off -site drainage is not taken into account for low -density projects so this item should be zero. FEI Response: Comment Noted. Item has been corrected. iii. "On -site Buildings/Lots" - This value should be the total amount of BUA allocated to the individual lots (91,000 sf) not the BUA allocated to each individual lot. FEI Response: Comment Noted. Item has been corrected. Also, application has increased the lots from 26 to 28 with the addition of 7,000 sf (total — 3,500 sf/lot) 4. The following issues were noted with the Supplement-EZ Form: a. Cover Page: i. Line 7 - Please indicate the width of the required vegetated setback from on -site surface waters (in accordance with 15A NCAC 02H .1017(10)). It is noted that there are no surface waters located on -site for this project, however the required setback distance should still be listed on this form. FEI Response: Comment Noted. Even though setback do not exist on this site, the minimum of 30' was used. b. Drainage Areas Page: i. Line 9 - This item is the total amount of BUA allocated to the individual lots. Per the provided deed restriction document, each of the 26 lots is allocated 3,500 sf of BUA so this value would be 91,000 sf (145,460 sf shown). FEI Response: Comment Noted. BUA for the lots was increased to 98,000 for 28 lots. The total ISA now becomes 152,460 SF. ii. Line 10 - This item is the total amount of BUA allocated to the common areas (i.e., not allocated to the individual lots) and is equal to the sum of the items listed on Line 12, 54,460 sf (zero sf shown). FEI Response: Comment Noted. BUA has been updated. NCDOT requires that Verdant Lane to be installed in the future. That ISA allocation was pulled out of the roadway quantity and reclassified as future. iii. Line 12, Roof - This item is the total amount of common area roof. Since there are no roofs proposed in the common areas, this item should be zero sf. !!:rAFEI Civil Engineers and Land Surveyors FEI Response: Comment Noted & corrected. iv. Line 19 — This item is not required for low -density projects. FEI Response: Comment Noted & corrected. c. Low -Density Page: FEI Response: Swales have been updated and recalculated based on the modified storm drainage layout. i. Slope Column — The values shown in this column should be shown as a percentage, not as ft/ft. Please revise. FEI Response: Comment Noted & corrected. ii. Swale 5, Pervious Area Column — This value is shown as "-0.01". This value should not be negative. Please revise as needed. FEI Response: Swales have been updated and recalculated. 5. Please upload the electronic files from the initial submissions at the following link: https://edocs.deq.nc.gov/Forms/SW-Supplemental-Upload. It appears that the email letting you know that we have accepted the project for review and instructing you to upload the electronic files was not sent out to you on March 3, 2022 when we accepted this project. Please upload those files at this time. This item is required per 15A NCAC 02H .1042(2). FEI Response: Original files were uploaded on 5/24. This submittal will be uploaded on 6/6. 6. Provide PDFs of all revisions, 2 hardcopies of revised plan sheets, 1 hardcopy of other documents, and a response to comments letter briefly describing how the comments have been addressed. FEI Response: Comment Noted. a. PDFs must be uploaded using the form at: https://edocs.deq.nc.gov/Forms/SW-Supplemental-Upload b. Hard copies must be mailed or delivered to the following address: i. For FedEx/UPS: Jim Farkas 512 N. Salisbury Street, Office 640E Raleigh, NC 27604 !!99"_ FEI Civil Engineers and Land Surveyors ii. For LISPS: Jim Farkas 1612 Mail Service Center Raleigh, NC 27699-1612 Feel free to let us know if there are any other changes/modifications. !!:rAFEI Civil Engineers and Land Surveyors