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Home My WebLink AboutWPO202000044 Correspondence 2021-02-23SHIMP ENGINEERING, P.C. Design Focused Engineering February 17', 2021 John Anderson County of Albemarle Department of Community Development 401 McIntire Road, Room 227 Charlottesville, Virginia 22902-4596 RE: Response Letter #1 for TENPAS RESIDENCE - VSMP Dear Anderson, Thank you for your review of the VSMP Plan Tenpas Residence. This letter contains responses to the VSMP comments dated January 15, 2021. Our responses are as follows: A. Stormwater Pollution Prevention Plan (SWPPP) The SWPPP content requirements can be found in County Code section 17-405. A SWPPP must contain (1) a PPP, (2) an ESOP, (3) a SWMP, and (4) any TMDL measures necessary. 1. Submit SWPPP for single-family construction. Please use county template (SF SWPPP). Link to template will be sent to Michael Chandler and Kelsey Schlein. (Rev. 1) Addressed. 2. Include reference to WP02020-00044 in single-family SWPPP title. (Rev. 1) Addressed. 3. New: Please revise SWPPP title page Construction Activity to match site location (Albemarle). The SWPPP title page has been updated to match the site location in Albemarle County. 4. New: With change instate VAR10 CGP reporting requirements, DEQ requires local authorities issue a generic coverage letter and VAR10 for single-family construction area of land disturbance > 1 Ac. This project qualifies. Please revise SWPPP to include attached coverage letter and attached (generic) VAR10. The SWPPP has been revised to include the VAR10 letter. B. Pollution Prevention Plan (PPP) — See Sec. A above. Single-family SWPPP with VSMP /WPO plan will suffice. (Rev. 1) Addressed. The PPP content requirements can be found in County Code section 17-404. C. Stormwater Management Plan (SWMP) VSMP Regulation 9VAC25-870-108 requires the VSMP authority to approve or disapprove a SWMP. This plan is disapproved for reasons listed below. The stormwater management plan content requirements can be found in County Code section 17-403. 1. Compare level spreader detail, C7, with details shown with VA DEQ Spec. No. 2, Fig. 2.413, and ensure profile and plan ELS details from DEQ specification display clearly on the plan. (Rev. 1) Addressed. [image included with initial comments removed with Rev. 1 comments.] 2. C7 /Level spreader -Typ. detail (Rev. 1) Addressed. a. Include schematic representation of the ELS structure (concrete or timber). b. Provide x-sectional dimensions (W x D). Specify length. c. Also, recommend see VA DEQ Stormwater Design Specification No. 2,-Fig. �.J, below. [image included with initial review removed with Rev. 1 comments.] d. Include underdrain in C7 detail to prevent ponding /nuisance conditions; ref. Fig 2.3. e. Daylight ELS underdrain. (Although C7 detail is descriptive, it lacks clear structural element and underdrain.) 3. Ref. email sent 10/28/2020 11:16 AM (to SE) on topic of stormwater quality requirements; revise plan accordingly. Recommend standalone SWM plan sheet. Also, ESC plan review comment item 3.b., below. (Rev. 1) Not addressed. Please consider (attached) email, and revise design, accordingly; partial /relevant email text: `0.9 lb. phosphorus reduction is required: either purchase nutrient credits, or on -site SWM; either is fine. 17-403.13 allows Agreement in Lieu of a SWM plan at Administrator's discretion. It is not automatic. SE in fact has likely prepared single-family VSMP applications (equivalent scale) with on -site SWM facilities, or nutrient purchase. This is no different, and unless SE has coordinated this project with the county engineer and SHIMP ENGINEERING, P.C. Design Focused Engineering has received advance assurance that a SWM plan was not or would not be requested or expected, then similar to administration of comparable single-family residences (2.76 Ac. LOD, 0.45 Ac. new impervious area), stormwater management quality requirements (9VAC25-870-65) apply. 9VAC25-870-65 specifically mandates application of VRRM.xls. Again, we will send VRMM.xls acceptable to Engineering based on soils maps incl. with Cale. packet.' Also: a. Revise SWM Narrative, C5, to: i. Reference SWM quality requirements, The SWM Quality requirements have been referenced and addressed. Sheet C5 now includes a revised narrative that states water quality compliance with 9VAC25-870-65 is addressed through dedication of 3.28 acres of open space in D soils. ii. Revise text /typo to ref. 9VAC25-870-65 (quantity). The SWM Quantity compliance reference has been revised to state compliance with 9VAC25-870-66.D b. Provide VRRM.xls /New development runoff reduction spreadsheet. The VRRM New Development Spreadsheet has been provided in the SWM packet. D. Erosion and Sediment Control Plan (ESCP) Virginia Code §62.1-44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan is disapproved for reasons listed, below. The erosion control plan content requirements can be found in County Code section 17-402. 1. Revise plan title to include ref. to WP0202000044. (Rev. 1) Addressed. 2. C3 (Rev. 1) Acknowledged. a. Note: VDOT Land Use permit required for work within public right -of way (driveway entrance). b. Note: VDOT entrance permit required; please coordinate with VDOT Charlottesville Residency. 3. C4 a. Cross-check sequence of construction phasing (C4) with sequences on C5 (ESC Ph-1), C6 (ESC Ph-2). (Rev. 1) Addressed. b. Stormwater Management Note: Address stormwater quality requirements (9VAC25-870-65). Also, see Engineering email sent 10/28/2020 11:16 AM. (Rev. 1) Not addressed. Also, item C.3., above. The SWM Quality requirements have been addressed and the stormwater management narrative on sheet C5 has been revised to mention compliance with 9VAC25-870-65 through the dedication of 3.28 acres of Open Space. 4. Check /revise sequence of construction text items 1-6, CS C6, for accuracy; for example: (Rev. 1) Addressed. a. Ruritan Lake Road may require revision. (Rev. 1) Addressed. b. Reference to sediment basin may not apply. (Only sediment trap with this design). (Rev. 1) Addressed. c. New: Revise Sequence phase 2, Note 81 to require ESC inspector approval prior to removal of ESC measures. The sequence of construction for phase 2 note 8 has been revised to require ESC inspector. d. New: Revise SWM Narrative to ref. 2.81 Ac. land disturbance, consistent with plan, and text, elsewhere. The SWM narrative reference to land disturbance has been revised to 4.21 aces. 5. C6 (Rev. 1) Partially addressed;follow-up at item. 5.e., below. a. Label sediment trap (ST) floor dimensions. b. Remove proposed grading from stream buffer. (Slight amount of grading appears within 100' stream buffer.) c. Label ST weir L x W x D dimensions. d. Label driveway width. C6 e. Provide culvert 2 profile. (Rev. 1) Partially addressed. As ollow-up: Provide OP at lower end of pipe. Relabel `inlet protection.' Outlet protection is provided at the outlet of culvert 2. f. Show /label riprap OP, culvert 1, 2. g. Show roadside ditch between elevation 610' and culvert 2 on west side of driveway. Runoff from driveway surface will erode /create a ditch unless controlled ditch section is defined with design. h. Provide ditch x-section; item g., above. i. Provide check dams, as needed, for ditch, item g., above. 6. CS a. Provide additional existing contour labels. (Rev. 1) Partially addressed. As follow-up: Please revise contour labels to dark black (color) as opposed to faint gray, for readability. The contour labels have been revised to show as black. b. Revise CE label to read PCE (paved construction entrance). (Rev. 1) Addressed. c. Revise ELS length based on Qian (2.93cfs . Ref. VA DEQ Stormwater Design Specification No. 2, Table 2.2, and pg. 14. (Rev. 1) Not addressed. Design does not acknowledge initial explicit reference to BMP standard (VA DEQ Stormwater Design Specification No. 2) 10-yr frequency storm. Please respond to comment; revise ELS length to 3838ft., minimum. Please call if any questions. The ELS has been expanded to 40-ft. d. Show break in silt fence (SF) below ST weir. (Rev. 1) Addressed. Across sheets (C2, C3, C5, C6): Revise stream buffer linework (at pond) near entrance on Wesley Chapel Road, since buffer extends SE and downstream to adjacent property line. (Rev. 1) Addressed. GIS: [ image included with initial review removed with Rev. 1 comment.] If you have any further comments or questions, please feel free to contact me at 434-227-5140 or my email at Michael@shimp- engineering.com or you may contact Justin Shimp at Justin@shimp-engineering.com. Regards, Michael Chandler Shimp-Engineering, P.C.