Loading...
HomeMy WebLinkAboutWPO202200024 Correspondence 2023-04-10 (2)J'AmericanHelios "` CONSTRUCTORS Utility Scale and DG Solar. Rivanna Solar WPO Comment Response Review Comments Reviewer Response Res onder Shaw and label all required easements on the plans, including access easements to proposed facilities. Easements will be AUil WeMlantl- Albemarle County See exhibit 2, final easement locations and sizes to be coordinated American Helios dedicated to public use and should include all the measures used with owner for DEQampliance. A plat and deed of dedication for the stmmwacer facility easements will need to be recorded priorta approval afthe Mail Wantland - Albemarle County (Rev.1) Comment not addressed. Response noted. American Helias VSMP and site plans. DEQ water quality and water quantity requirements will need to be met Include all calculations regarding these requirements (runoff talks, VRRM spreadsheet, BMP calks, etc.). The existing site candidion for this project area should be forested andthe Mail Wenland- Albemarle County Noted, please we SW Nate sheets, HIM report, and VRRM Results American Helios posts and beams along with roads and buildings should be included in the impervious. [WAC25-87665,66] Show the dry, swales and any additional measures at a larger Dry Swales removed in favor of Extended detention basins, all scale. Any concentrated flaw from the measures that cutlet into Will Wantland! -Albemarle County basins meet l year 24 hour starm energy balance requirements. See American Helias natural channel will need to meet energy balance. SW-102 for results Will grading be required for the panels or mats? If so, it will need Mail Wardand- Albemarle County Road grading has been added on plans far visibility reasons. American Helias to be shown an the plans. Provide additional information on the mitigation plan, including areas of mitigation and the species and quantity of plants. Any Mail Wentland- Albematle CountyThis required red information has been added American Helias areas of plantings outside afthe buffer fie -Albemarle GIS) will need to be in an easement (link to additional materials in email). The dry swales are still difficult to see. Consider using different line types and weights for the existing and proposed contours. Include the drainage areas to the dry swales, the maximum is 5 res. They are also concentrating the Flow and will need to be Mail Wenland- Albemarle County (Rev. 2) Swales are no longer shown. American Helias released into an adequate channel. Energy Balance will also he required far concentrated Flows entering a natural channel. (DEQ IMP Ditches created by the road grading will also need to he designed and meet the DEQ recommends. (Rev. 2) Comment not Mafi WerdaM-Albemarle County Road grading has been added on plans far visibility reasons. American Helias addressed. The road grading is no longer shown on the plans. The disturbed area in the VRRM appears to be larger than what is actually disturbed. Also, undisturbed areas (especially in the buffer) an he used as Forest & Open Space for additional credits (Forest It Open Space will need to he platted, please contact me Mail Werdand-Albematle Counly VRRMspreadsheetrawltsprovided American Helias far additional information if this might be something you want to pursue). (Rev. 2) The VRRM and methods to meeting DEQ quality I am awaiting a response regarding how to handle the easements Mail Wendand-Albemarle County (Rev. 2) The easements will he assessed with the plat submittal. American Helios and will let you know when that is finalized. Pipes will need to be buried to avoid maintenance and erosion issue. All outlets will need to be into flannel and Energy MaRWanland-Albemarle County Channels pravided in place ofaverland pipes American Helios Balance will need to be met. The tables on SW-102 will need to include the Qallowed/Qdeveloped From the Energy Balance equation and the Qactual/Qpost from the storm muting. Include the muting Will WeMland- Albematle County Please see SW-103 far updated tables American Helias calculations with the submittal. The Q10 pre and post will also need to be shown to verify DEQ flood protection. Include the arlfce inverts on the profile views of the basins. Also Mail Wantland - Albematle County This has been added American Helias show the tap of berm. Diversion Dikes cannot be used as a permanent measure due to their limited life and maintenance requirements. These should be Mail Wentland- Albematle County See SW-208 for ditch design/detail American Helios replaced with ditches and should include the design calculations far the ditches. Some of the drainage areas appearta he incorrect and should be verified. An example is on sheet ESC-208 neartap 11 where the Mail Wenland- Albemarle County Drainage areas have been updated American Helias line is parallel to a centaur. The conservation area shown on the plans that is being used in Mail Wenland- Albemarle County This has been updated an the plans American Helios the VRRM should he labelled as'SWM Forest and Open Space'. Show all the proposed grading an the plans. There appears to be cantaurs shown on the mars that do not tie iota the existing Mad Wenland-Albemarle County Updated mad contours to include daylight lines American Helios cantaurs. label the max slopes of the roads. Use the US Fish and Wildlife link in the email to determine if this Mail Wenfland-Albemarle County This is not located in the critical habitat fare species. American Helias project is in a critical habitat for endangered species. Use details from the Virginia Erasion and Sediment Control Will WerdaM-Albemarle County I (Rev. 1)Comment American Helias Handbook. partially addressed, see comment 4 below. Perimeter matrals will be needed around all areas of land disturbance, including tree removal. (Rev. 1) Comment not addressed. All cantral measures should be from the Virginia Erosion and Sediment Cantral Handbook (VESCH). H is unclear what a sediment swale is and it does not appear to he in the VESCH. There is also no measures shown far Mail WeMland- Albemarle County Removed diversions nut leading to a channel American Helios the stream crassings and silt fence cannot be used for storage. (Rev.2) Comment partially addressed. Some of the diversians do not appear to lead to a channel (sudr as on sheet ESC-203). Al diversions will need to lead to a stabilized outlet or other are (VESCH 3.09). See also comment 5 below. far silt fence, the maximum drainage area is no more than one quarter acre per 100 feet of silt fence and the maximum slope length behind the harder is 100 feet. Consider diversion dikes to sediment traps or basins for the measures.(VESCH 3.05](Rev. 1) Mail WeMlantl- Albemarle Courtly Re -added the sih fence detail as well as utilized it in specifc American Helios See previous comment (Rev. 2) Comment partially addressed. It locations appears the silt fence was removed though it would still b , a good option in many areas. Per comment 1 above, it may be required by the inspector. One is the compliance with the VRRM. Everything has been put into the Sheet flow to Conservatian Area, however (as discussed in earlier meanings) the site is not conducive to this due to the slopes and there are also no level spreaders shown an the plan as required by the DEC, specifications for that measure. The basins that are designed to the Extended Detentian Basin Specification The VRRM hspreadsheet has been updated. There are 3.251hs./yr. of VRRMad (DEQ IMP Spec No.15, line Be an the VRRM, I don't believe any Mail WeMlarq- Albemarle County Tl union required. American Helios are designed to the line So spec) can be used and entered into the spreadsheet and the grass channels (line 4 on the VRRM) that meet DEQ IMP Spe, No. 3 an also he used for compliance. Please be sure to read the DEQ BMP specifications to ensure that what is shown an the plans and used in the VRRM is designed to those standards and provide a revised VRRM spreadsheet. The 1-yr Q allowed calculation has been updated to include two significant digits past the decimal point. The 1-yr Rv Developed is now shown in the table an sheet SW-102. Another is with the quantity calculations. The 1-yr Qallowed per basin column on SW-102 is showing whale numbers and I The 10-yrQ pre and Q post are now included an SW-103. The Q wouldn't expect this if Rs the number from running the energy actual at the basin curtails is shown on SW-103.The basin outfall balance equatian. I was unable to AeA as the RV-develaped was channels have been repositioned to outlet at locations within not shown in the table. Also, the Q-pre and the Q-developed in channels where the Q10 post construction is less than or equal to the 10 year table an SW-103 were the same numbers and that's the Q10 pre-constructan. not something we see as there is always some difference. As Mafi Wantland - Albemarle County American Helios previously discussed, energy balance is not something that fallouts have been added in the hydraulic calculations package to applies to the SO -year rtann, the post just needs to be less than indicate the storm event routing for the basin orifices and the pre. Additionally, going through the calculations package I did emergency spillways that camespond to the tables on SW-102 and not see routing resuhs that mavAed to the numbers provided in SW-103. The hydraulic calculations do not indicate the 1-yr or 10-yr the tables on SW-102 and 103 or the water surface elevations storms overtopping the emergency spillways. Additionally, the inside the ponds far the design storms. routing hydragraphs indicate appropriate drawdawn times. Water surfaces have been added to the basin details. The water surface elevations are typically the same elevation as the respective curtail mifa.