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Home My WebLink AboutWPO201500055 Correspondence 2016-01-19TIMMONS GROUP YOUR VISION ACHIEVED THROUGH OURS. January 19, 2016 John Anderson Albemarle County Community Development 401 McIntire Rd, Rm 227 Charlottesville, VA 22902 111 West High Street P 434.295.5624 Charlottesville, VA 22902 F 434.295.8317 www.timmons.com RE: VSMP Permit Plan Review - Branchlands Whistler House —Comment Response Dear Mr. Anderson: We have reviewed all of your comments from December 15, 2015 and made the necessary revisions. Please find our responses to the comments below in bold lettering. VSMP: SWPPP: Stormwater Management Plan (WP0201500055) 22. C5.1 — WEIR Plate in Str. 106 Detail — Show top of structure (top of weir/top of storage are shown). C6.0 shows Str. 106: MH- I W/ WEIR PLATE, TOP = 430.04'. (Rev. 1) Partially addressed. Str. 106 Detail. Please review 10 yr-WSE which appears to be high/in wrong location. The 10 yr WSE has been updated. See "Weir Plate in Str 106 Detail" Sheet C5.1. 28. C6.0 — Profile, Str. 200-204: Label horizontal separation between steel plate weir wall and end wall of 60" CMP storage pipe. Consider maintenance, and design reasonable access to this space. With 1.0' Max clearance above the weir plate (rapidly diminishes since circular), it is likely not possible to access the downstream side of the weir plate in the 60" system, should need arise. (Rev. 1) Partially addressed. As follow-up: 60" system 6" orifice detail elevation inconsistent with profile elevation. Please revise. The 6" orifice elevation on the profile view has been updated to be 433.50'. See "Str 200 — Str 204" Profile Sheet C6.0. 33. C6.0 — Provide / show Manway structures for StormTech and 60" CMP storage pipe systems in profile views. Section views of both the CMP pipe and arched chamber system have been provided. These details show manway access/inspection ports and detail out how they connect to the system. Per the manufactures recommendation manway access is not provided for the arched storage system. These systems are inspected and cleaned out via inspection ports. See Sheet C5.1. CIVIL ENGINEERING I ENVIRONMENTAL I SURVEYING I GIS I LANDSCAPE ARCHITECTURE I CONSTRUCTION SERVICES 34. C6.0 — Specify gauge (steel thickness) of 60" CMP storage pipe system and both weir plates, if not shown. Weir plate gauge thickness has been added to both weir plate details on Sheet CS. 1. Gauge thickness of the 60" storage pipe has been shown on the provided manufacturer's details on Sheet CS. 1. VSMP: SWPPP: Erosion Control Plan (WPO201500055) 3. C3.1 — Label floor of sediment trap, plan view (I 6'x 52'). (Rev. 1) Partially addressed / misunderstanding. As follow-up: please add sediment trap floor dimensions to plan view: (16' x 52'). Dimensions have been added to the sediment trap see Sheet C3.1. Additionally the sediment trap detail has been updated to reflect the correct dimensions (23'x68') see Sheet C3.0. We have included PDF copies of the plans and calculations for your review. If you have any questions or comments, please feel free to give me a call at 434.964.7148. Sincerely, Craig Kotarski, PE Project Manager .�tlES TIMMONS GROUP YOUR VISION ACHIEVED THROUGH OURS. November 17, 2015 John Anderson County of Albemarle Community Development 401 McIntire Road Room 227 Charlottesville, Va. 22902 -4596 RE: WP0201500055 Branchland Whistler House — VSMP - Comment Response Letter Dear Mr. Anderson: We have reviewed all of your comments from October 8, 2015 and made the necessary revisions. Please find our responses to the individual comments below: 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 ESCP, (3) a SWMP, and (4) any TMDL measures necessary. Comments reference binder dated 22 Jun 2015 — Recommend do not re- submit SWPPP until ESC /SWM plan comments addressed. SWPPP contains reduced -size ESC and SWM plans. Acknowledged. The SWPPP shall be resubmitted at a later date. I. Sec. 1, Registration Statement — please sign /date. 2. Sec. 4,5 — Revise per comments. Recommend wait until ESCP /SWMP comments addressed. 3. Sec. 6 — Revise I I " x 17" PPP Exhibit: Relocate mortar mix /concrete washout so distant from future bioretention. Describe berm containment: impermeable heavy -mil liner /Volume sufficient to contain stored fuel volume + 10 %. Show solvent /paint /chemical storage. Add SF or similar downslope of temporary toilets. Show non - hazardous solid waste collection (dumpster) draining to ST, or equivalent. Show sediment basin or equivalent to capture wash waters. 4. Sec. 6.c. — Delete 'No concrete washout shall occur on site. 5. Sec. 6.c. — Delete `Existing basketball court to the north.' 6. Sec. 9 — Certification Statement: sign /date. 0 0 6 C cu t C d V C v E a 0 a CD CD a m M N V- M Ir El. N %0 L'i Ln 01 N M E 0 u M C O E November 18, 2015 Page 2 of 7 B. VSMP: SWPPP: Stormwater Management Plan (WPO201500055) VSMP Regulation 9VAC25- 870 -108 requires the VSMP authority to approve or disapprove a SWMP. This plan is disapproved for reasons provided in comments below. The stormwater management plan content requirements can be found in County Code section 17 -403 I. CO.0 — Revise Title: Branchlands Memory Care and Assisted Living, VSMP WPO201500055 The title has been revised. See Sheet C0.0. 2. Remove sheets CIA Cl. I, L -001. Please mark through sheet numbers in index. Sheets C 1.0 and C 1.1 have been removed from the plan set. However, the landscape plans are still included as they contain information on the Bioretention plantings. 3. C3. I — Revise IP @ Nyoplast overflow structure. Bioretention may not be installed until all upslope areas are stabilized. IP will not be required for bioretention overflow structure. This inlet protection has been removed from the plans. See "Phase 11" Sheet C3.1. 4. C4.014. I — Revise sheet titles to `Site Layout' or similar. A VSMP may not approve a site plan. The title of these Sheets has been updated. See Sheets C4.0 & C4.1. 5. CO.0 —Edit index. Ref. item #4. The sheet index has been updated. See Sheet C0.0. 6. C4. I —Label pipe structure # 105. This pipe has been labeled. See "Grading and Drainage" Sheet C4.0 7. C4. I —Label DI structure # 108. This structure has been labeled. See "Grading and Drainage" Sheet C4.0. 8. C4. I — Revise bottom of bioretention label to read floor elevation (or grade elevation) of bioretention. This label has been updated. See "Grading and Drainage" Sheet C4.0. 9. C4. I —Label bioretention clean -out. Label bioretention overflow structure. Both the cleanouts and overflow structure have been labeled. See "Grading and Drainage" Sheet C4.0. 10. LD -229: Storm Sewer Design Computations —in this (or separate table) list pipe structures # 109, 107. These pipes should be considered a part of the stormwater detention system as they are upstream of the control structure. Therefore adding them to the LD -229 to verify pipe adequacy is not necessary as they are designed to allow water to back flow from the control structure into the underground storage system. 11. C6.0 —Pipe Str. # 109 (6.83' of 15" HDPE), 107 (22.74' of 15" HDPE) @ 0.00% slope is problematic. Revise to provide positive slope at least 0.5 %. November 18, 2015 Page 3 of 7 The slope of these pipes has been updated to be 0.50 %. See Sheet C6.0. 12. C4. I —There appears to be no MH access to either ADS "Stormtech" System (Area to W), or 3 -line, 125' L 60" DIA storage system (Area to S). Provide manway access to each system. Manway access has been provided to both systems. See "Grading and Drainage" Sheet C4.0. 13. C4. I — Provide notes, labels, or detail that shows how the two 50' lines of ADS system make connection, with particular emphasis on Access for maintenance. Ensure that each line is accessible. Provide some for 60" DIA, 125' L detention system (Area to S). All detention system lines must be accessible. Design should ensure debris accumulation will not block, back -up, or short - circuit either system. Access has been provided to each system. See "Grading and Drainage" Sheet C4.0. See Sheet C5. I for detail on how the connection to the ADS system is made. 14. C4.1 — Provide new Str. #104 away from biofilter; use Std. MH. The biofilter 24" Nyoplast overflow structure (dome drain) will be upstream of this MH. The Nyoplast structure is ineligible as an inline storm system element. Organic debris is likely to collect at the base of the overflow structure. Any obstruction of the 24" (dome drain) overflow structure will compromise the entire Area to W storm runoff system. An additional manhole has been added to the storm system. The biofilter overflow structure (Structure 104A) is upstream of this manhole (Structure 104). 15. C5. I — Recommend revise elevation of 4" perforated underdrain to 424.33' (biofilter). The underdrain elevation has been updated to 424.33'. See Sheet C5. I. 16. C5.0 or C5. I —Add Note: Bioretention may not be installed until all upslope areas are stabilized. IP will not be required for bioretention overflow structure. This note has been added to the Bioretention detail. See Sheet C5.1. 17. C5.0 or C5. I — Provide bioretention planting schedule. Bioretention planting schedule has been provided. See Sheet L -1. 18. C5. I — Revise `bottom of biofilter 427.50' to read top of biofilter Mix. This note has been updated. See Bioretention Detail Sheet C5.1. 19. C5. I —Label elevation /top of biofilter cleanout: set Elev. at least 4 -6" above 3" hardwood bark mulch. The top elevation of the biofilter cleanout has been added to the plans. See Bioretention Detail Sheet C5.1. 20. C5. I —Label %slope of line between biofilter overflow structure and new MH (2% Min). Also, items #14,29. The slope of this pipe has been labeled. See "Bioretention Detail" Sheet C5.1. November 18, 2015 Page 4 of 7 21. C5. I — Provide plan view, Str. # 106. Plan view /design must provide means of clearing pipe # 107 of debris. Pipe 107 shall be cleaned by flushing the pipe out from structure 108. This will then allow any debris in the pipe to be vacuumed out of structure 106. 22. C5.1 —WEIR Plate in Str. 106 Detail —Show top of structure (top of weir /top of storage are shown). C6.0 shows Str. 106: MH -1 W/ WEIR PLATE, TOP = 430.04'. Top of the structure has been added to the detail. See "Weir Plate in STIR 106 Detail" Sheet C5.1. 23. C6.0 —Pipe #207, 205: Increase DIA to 15" Min. (Yard inlet system 12" DIA, is the exception). The size of these pipes has been increased to 15 ". See Sheet C6.0. 24. Revise LD -229 to reflect pipe DIA increase, item #23. The LD -229 has been update to reflect the increase in diameter. See Calculations Book. 25. C4. 1/C6.0 —It is unclear how Str. 112, listed as MH -1, functions. Str. is located in parking area that routes to UG Detention, but is not identified as a rg ate or DI. Confirm design; revise profile label as necessary. Str 112 is a manhole. Its purpose is to provide a connection point for building roof drainage. 26. C6.0 —Str 204 -218 profile: Revise label to read INV IN 435.00 (2 13) This label has been updated. See STIR 204 — STIR 218 Profile Sheet C6.0. PROP. GRADE 204: 60" CMP STORAGE PIPE TOP ELEV. 436.50 BOTTOM ELEV. 431.50 INV IN 435.00 (215) ti 636 Q� 57266 4? @Z�E @ EX. \ GROUND `213 8.63' OF ` 43 12" HDPE @ 2.32% 27. Revise Str. 213 DIA to 15" Min; this leads from a standard VDOT DI to the 3 -line 60" DIA UG Detention system. This pipe has been updated to 15 ". See "STR 204 — STIR 218 Profile" Sheet C6.0. 28. C6.0 — Profile, Str. 200 -204: Label horizontal separation between steel plate weir wall and end wall of 60" CMP storage pipe. Consider maintenance, and design reasonable access to this space. With 1.0' November 18, 2015 Page 5 of 7 Max clearance above the weir plate (rapidly diminishes since circular), it is likely not possible to access the downstream side of the weir plate in the 60" system, should need arise. Horizontal separation of 4' between the weir and the end of the pipe has been labeled. See "STR 200 — STR 204 Profile" Sheet C6.0. 29. C6.0 — Revise profile, Str. 100 -110. Provide Std. MH. Ref. item # 14, above. This profile has been updated to include the new manhole. See "STR 100 - STR 110 Profile" Sheet C6.0. 30. C6.0 — Provide profile for line from biofilter overflow structure to New MH. —Also, item #29 A profile for this line has been provided. See "STR 104A — STR 104 Profile" Sheet C6.0. 31. C5. I — Revise WEIR Plate in 60" System Detail. Show as circular (plate is circular). This detail has been updated to show the weir plate as circular. See "Weir Plate in 60" System" detail Sheet C5.1. 32. Provide documentation of purchase of nutrient credits: Nutrient credit purchase documentation will be provided closer to final approval. E. Documentation of the applicant's acquisition of nutrient credits shall be provided to the VSMP authority and the Department in a certification from the credit provider documenting the number of phosphorus nutrient credits acquired and the associated ratio of nitrogen nutrient credits at the credit - generating entity. Until the effective date of regulations establishing application fees in accordance with § 62.1- 44.19:20, the credit provider shall pay the Department a water quality enhancement fee equal to six percent of the amount paid by the applicant for the credits. Such fee shall be deposited into the Virginia Stormwater Management Fund established by § 62.1 - 44.15:29. C. VSMP: SWPPP: Erosion Control Plan (WPO201500055) Virginia Code §62.1- 44.15:55 requires the VESCP authority to approve or disapprove an ESCP. This plan is disapproved for reasons provided in comments below. The erosion control plan content requirements can be found in County Code section 17 -402. C3.0 — Sediment trap design Elev. vs wet /dry storage —if table presents Vol. per I ' vertical interval, please clarify. It appears, for example, that Elev. 423.7' provides <43.4 cy storage, when it may provide < 80.4 cy. Please Add note or revise volume(cy) heading to indicate incremental storage ( /I' interval). Revise values as necessary. The volumes shown are incremental storage volumes. The detail has been updated to reflect this. See Sheet C3.0 November 18, 2015 Page 6 of 7 Sediment Trap design drainage area (acres) ( <3) 0.91 trap volumes: CREST OF STONE WEIR elevation (ft) area (sf) volume(cy) A HD \ 422 859 423 1139 37.0 ORTSTORAGE 424 1203 43.4 425 1385 47.9 426 1573 WET STORAGE toocwArsO) wet storage: wet storage required (cy) (67"13A) 61.0 bottom of stone weir (ft) 423.7 iLTFR "OOTR ` °GKKR,NAI nev CM/6E AGMWrATE CEASS I RV wet storage provided at this elevation (cy) 63.0 * "coarse aggregate shall be VDOT#3, #357 of 45 slope ofwet storage sides 1:1 weir length (ft) (6x DA) 15.0 dry storage: bottom of trap elevation (ft) 422 dry storage required (cy) (67 *DA) 61.0 bottom trap dimensions: 16'x52' crest of stone weir 425.0 top of dam elevation (ft) 426 dry storage provided at this elevation (cy) 61.0 top width of dam (ft) 2 slope of dry storage sides 1:1 top trap dimensions 18'x76' 2. C3.1 — Revise ESC Legend, soil stabilization blanket =BM. The ESC Legend has been revised. See Sheet C3.1. 3. C3. I —Label floor of sediment trap, plan view (16' x 52) The floor of the sediment trap has been labeled. See Sheet C3.1. 4. C3.1 — Provide vegetative cover hardier than grass for proposed 2:1 slopes along SW edge of building. (ACDSM 8.A.2.); Ref. Phase 11. The proposed planting in this area is a mixture of trees, shrubs, native grasses, and wild flowers. See Sheet L -1. 5. C3.1/C5.1 — Specify material (Elev. 421' to 424) to replace excavated material beneath bioretention since C3. I stipulates removal to Elev. 421.00'. The note on Sheet C3.1 has been updated to specify that this will be accomplished with on -site fill dirt. EXCAVATE AND REMOVE SOIL TO AN , ELEVATION OF 421.00 IN ALL.AREAS WHERE SEDIMENT TRAP FOOTPRINT OVERLAPS 13108EETENTION i FOOTPRINT BEFORE. INSTALLING f B10RETEj4T1 N MU ,1 ITS LEAIj1NG ' Pv, AND G AIDING RED 6. Show soil stockpile location, if any. A soil stockpile location has been shown on Sheet C3.1. November 18, 2015 Page 7 of 7 We have provided a pdf of the revised plans for your review. If you have any questions or comments, please feel free to give me a call at 434.327.1688. Sincerely, Craig Kotarski, PE Project Manager