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Home My WebLink AboutSW1200601_2020-07-22 comment response_20200722 July 22, 2020 NCDEQ Attention: Jim Farkas Regarding: Request for Additional Information Stormwater Permit No. SW1200601 Sanstone Office & Storage Expansion Henderson County Dear Mr. Farkas: Please find attached our re-submittal for the SANSTONE OFFICE & STORAGE EXPANSION project. In addition, please find below our responses to your checklist of additional items required in bold. 1. Please include the property owner information in Section III, 2. This project appears to have two different property owners. In addition to what is provided, please add the following: a. Book 3373, Page 444 (3) – This property is owned by Christopher Sprenger & Michael D. DeLoach. Since the Property Owners are different than the Applicant, the Property Owner information should be completed (Section III, 2) and the Property Owner Authorization (Section IX) should be completed. A recombination plat was filed on June 10, 2020 after the original submittal to NCDEQ. I have included a copy for your records. At this time Henderson County has not updated the PIN. The owner for the combined parcels is Sanstone Home Office Properties, LLC. b. Book 3130, Page 466 (3) – This property is owned by the Applicant, Sanstone Home Office Properties, LLC. The “Property Owner” box should also be checked off (Section III, 1c). The property owner box has been checked on the included revised form. 2. Per the guidance on the Application, there should only be one drainage area per proposed SCM (Section IV, 9 & 10). Since there is only one proposed bioretention cell, there should only be one drainage area, the area draining to the proposed SCM. The drainage area table on the application has been revised to only included one drainage area, the area draining to the proposed SCM. 3. Off-site drainage areas draining to the proposed SCM must be accounted for by either: a. Assuming that the off-site areas are at their full build-out potential, per 15A NCAC 02H .1003(3)(b). Off-site impervious areas draining to the proposed SCM cannot be used for treatment credit unless there is a legal agreement in place (See below). b. Having a recorded legal agreement in place between the Applicant and the Owner of the upstream property in which the Owner of the upstream property agrees to record a deed restriction limiting the minimum/maximum amount of BUA on the upstream property that will be treated in the Applicant’s SCM, the locations and sizes of access and drainage easements, how construction and/or ongoing maintenance costs will be handled, maintenance responsibility, a list of legal recourses available to each party should one party fail to hold up their end of the agreement, and any other related legal issues. The revised plans show offsite drainage from the parcels west of the site being routed to bypass the SCM with swales (SW1 & SW2) located at the back of curb. There is a small amount of offsite area (0.39 ac) that is associated with the connection to the existing driveway and the planted buffer for The Lodge at Mills River-Sanstone Health & Rehab (Henderson-Beystone Parcel). The SCM and storm drainage network are sized to handle the additional drainage, but is not intended for treatment credit. 4. Please identify, dimension, and label all surface waters on the plans (Section VI, 8h) and show the required vegetated setback (Section VI, 8p). Please also include the water surface area in Section IV, 6 and recalculate Section IV, 7 & 8. The provided USGS topographic map indicates that there is a stream in the southwest corner of the property. Information on surface waters and vegetated setbacks can be found in 15A NCAC 02H .1017 (10). Per the onsite meeting with Isaiah Reed 07/14/20, there are no surface waters located within the project limits. 5. Please dimension the property boundary with bearings and distances on the plans (Section VI, 8i). Dimensions for the property boundary per the recent recombination plat have been included on the revised plans. Note that the site area changed from 6.02 acres to 6.00 acres. 6. Please identify and dimension all BUA on the plans (Section VI, 8j). The information entered into the Application and Supplement-EZ Form should be verifiable from the plans. For example, the buildings are well labeled whereas the roads, sidewalks, and off-site areas are not, there are some dimensions shown, but the areas cannot be verified. Additional labels added to Sheet C-5.0 to identify all proposed BUA. 7. 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). Per the National Wetlands Inventory and my own field investigation, there is no indication of wetlands on the site. Exhibit included in the report (Appendix I). Note added to the existing conditions sheet (C-2.0). 8. Please provide the boring log for the SHWT assessment (Section VI, 9). SHWT report with boring log included in Appendix I. 9. Please ensure that sufficient BUA is being treated within the proposed SCM (General MDC 1 & 15A NCAC 02H .1002(43)). Of the total proposed BUA, 99.3% is treated by the proposed SCM. A small portion (431 SF) of the proposed northern driveway bypasses storm structures ST15 & ST17. However, this is offset by capturing 833 sf of the southern driveway connection which is technically offsite BUA. 10. Please provide and show on the plans the SCM easement and maintenance access (General MDCs 8 & 9). SCM easement and maintenance access added to the plans, refer to sheet C-5.0. 11. Please add a note to plan sheet C-5.2 stating that the media should not be mechanically compacted (Bioretention MDC 8). This note per Bioretention MDC #8 has been added to Detail #4 on Sheet C-5.2. 12. It appears that there will be some BUA built outside of the project property. Please provide a legal agreement between the Property Owner (Henderson-Beystone Healthcare Properties, LLC) and the Applicant giving permission for this work to be performed. The Henderson-Beystone Healthcare Property is part of a separate entity, but is associated with Sanstone (the facility is called The Lodge at Mills River – Sanstone Health & Rehabilitation). The registered agent and manager for both LLC’s is Christopher Sprenger. 13. Please correct the following issues with the Supplement-EZ Form: a. Cover Page: i. Lines 2, 4, 7 – 10 – Revise as needed in accordance with earlier comments. After the determination, Lines 2, 4, 7-10 remain not applicable. b. Drainage Areas Page: i. General: 1. Line 5 – Line 5 = Line 6 + Line 7 + Line 9 + Line 13 Line 5 was updated for both columns. 2. Line 10 - Ensure that these values match and are consistent with the Application and the plan set (For example, the plans show 12,953 sf (12,953 sf = 9,089 sf + 3,864 sf) of buildings whereas the Application/Supplement-EZ Form show 13,976 sf) For this project, these values in the entire site column refer to all new BUA that will be added within the project area, broken down by type. These values in the drainage area 1 column refer to all new BUA that will be added within the drainage area to the proposed SCM, broken down by type. Line 10 revised to read 12,953 sf. ii. Entire Site Column: 1. Line 7 – For this project this value is the total amount of BUA that will be added within the project area. The items of Line 10 should add up to this item. Line 7 updated. 2. Line 8 – Off-site areas do not need to be reported in this column. Offsite area removed. 3. Line 9 – Normally, there are no off-site components to the entire site column, but since there is some BUA that will be added outside of the project site, all BUA that will be constructed outside of the project area can be listed on this line Noted. 833 sf accounting for the offsite driveway connection remains. 4. Lines 17 – 19 are not needed. Lines 17-19 revised as requested. c. Bioretention Cell Page: i. Line 18 – Since the SHWT was not encountered, enter the SHWT depth as “< 2,175.75”. Line 18 revised per your request. ii. Line 25 – The plans indicate that the peak attenuation outlet elevation is at elevation 2,182.0 ft (12” above the planting surface). Revise either as needed for consistency. Line 25 revised to 12” to reflect the outlet elevation. iii. Line 26 – Please provide a soils report showing the in-situ soil infiltration rate. Line 26 revised to “N/A” because the design includes an IWS. iv. Line 43 – Riprap is a form of energy dissipation, not pretreatment. Line 43 revised to no pretreatment. Note added in the comment section that riprap is still provided for energy dissipation. 14. 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 Let us know if there are any additional questions. Sincerely, Brandon M. Thomas, PE Project Engineer Brooks Engineering Associate, PA