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HomeMy WebLinkAboutWPO202200027 Checklist 2022-07-07Albemarle County Engineering Drainage Plan checklist for plan reviewers Updated 1 Dee 2014 A drainage plans is typically a component of a road plan, site plan, or stormwater management plan. It consists of the channel, ditch, culvert, and stormsewer design drawings, drainage maps, and computations for hydrology and hydraulics. Reference key; [Square Brackets] are County Code references, Turved Brackets � are policy references, and (regular parenthesis) are explanatory. Links to reference documents are provided where possible. A professional seal should be provided for any corfiputation packages where are separate from sealed plans. [I 8-32.6.2d. 14-305, 3111 inage area maps (This is a basic element, and without this there is no review) inage computations (usually in the form of tables from the VDOT Drainage Manual App. 913-1 LD-2014, App.7B71 LD-268, App., App.813-1 LD-269, etc. -computations are a basic element, and without them there is no review) all proposed and existing storm sewer must be shown in plan view for residential development, principle access free of flooding during the 25yr storm f 14- 410] v*" site runoff and entrances do not drain into streets (from VDOT Drainage Manual 9.4.5.2, 9.4.6.2) V-11 concentrated runoff (I cfs or greater) does not run across travelways/streets (as above following VDOT design) drainage does not nin across, through, or backwater in dumpstcr areas [ 184.12.19] overland relief is provided for any drainage structure or inlet in case of clogging. The failure of any system will not cause structures, streets or yards to flood. j Policy I direction of flow change (or deflection angle) in each drainage structure is 90 degrees or greater (flow should not have to reverse direction) (from guide of VDOT Drainage ,,�-Manual 9.4.9.3.2.3) V labels on all drainage structures provided (and should match the drainage computations and profiles) provisions and casements for drainage across 3 or more lots. Dense development where fencing, decking, sheds, patios, etc. are expected should provide yard inlets and pipes in easements, rather than ditches 1 Policyl Drainage profiles: (applicable to site plans, road and drainage plans) [ 14-311, 18-32] drain ge proftlesfor each pipe. structure or channel inust contain: existing ground proposed ground any channel linings all utility crossings a VDOT designation (MH- 1, DI-313, etc.) for each structure throat length for each drop inlet ,,grate type for each grate inlet V' a label on each structure to correspond with the computations Albernarle County Engineering Drainage Plan Checklist Page 2 of 2 — /" material and strength class or gage of each pipe — L7 manhole access every 300' for 15"-42" or 800' for 48" or greater pipe slopes at 0.5% min. to 16% max. (per VDOT studs for anchors over 16%) concrete inlet shaping (IS-1) specified on any structure with a 4' or greater drop 7 safety slabs (SL- 1) in any structure taller than 12'. &7�1 top or rim elevation for each structure V flow drop between inverts). all invert elevations for each structure (with positive end sections (ES-1) orendwalls (EW-I)on all pipe outlets. Endwalls for culverts 48" or taller scour outlet protection at all outlets, corresponding to computations (Green Brook, OP) Q 1 age computations: (applicable to any plan proposing pipes, channels, etc.) P mputations for all pipes L,-*� i7AIl proposed systems are designed within open channel flow capacities. (HGL computations are not necessary, and should not be relied upon unless the entire system is to be watertight.) For systems within drainage easements, all proposed pipes are a minimum 15" in diameter There are no excessive outlet vel4;ties �(>15fps(�' v C n '��i let computations for any curb inlets on grade All spreads are less than 10' V7' carryover is accounted for vl'�' 100% capture at entrances so no flow runs out entrances into travel lanes t7"' 100% capture, or overland flow of capacity storm, to stormwater management facilities. Typically stormwater management is designed to the 10year storm, and inlets on grade often cannot capture this. Inlets in sumps should be used. !��let computations for any curb inlets in sump conditions All flow depths are below 6" in the capacity table All spreads are less than 10' 100% capture to storrawater management facilities ditch computations for any ditches ilJA ditch linings specified per plans meet velocity requirements Culvert computations for any culverts OA headwaters < 1.5 x culvert height, and 18" below shoulder elevation of streets. 0 ti t protection computations for all outlets dimensions and stone sizes for all outfalls ed pipe and inlet drainage area map limits of all areas and sub -areas draining to proposed structures, and existing structures or channels which will be impacted acreage of each drainage area as used in computations hydrologic coefficient for each drainage area as used in the computations time of concentration for each drainage area as used in the computations destination structure labeled for each drainage area (if not obvious) Albemarle County Engineering Erosion and Sediment Control Plan checklist for plan reviewers January 24, 2022 (Use the latest checklist from the Team Services engineering forms site) An erosion and sediment control plan is a document which illustrates the measures used to control erosion and sedimentation during construction. All measures follow the Virginia Erosion and Sediment Control Handbook. Reference key: [Square Brackets] are County Code references, I Curved Brackets 1 are policy references, and (regular parenthesis) are explanatory. Ljnks to reference documents are provided where possible. Application information: _Z Completed WPO application and fees, with owners signature [County Cod 18-32.4.3.2, 18-32.3.9. 17 Article 11] Erosion Control plans require a Water Protection Ordinance (VvTO) application and original owner's signature. No review is provided without application, owner signature(s) and fees. This is true even for revisions. It is important that the owner be aware of comments and resubmittals, and this is the county assurance. Copies of federal and state permits for any wetland or stream disturbance (Army Corps, VDEQ, etc) [ 17-604, 18-32.1.2, 14-311 VSMP: SWPPP, PPP, SWMP approvals obtained where necessary. In most cases, the erosion control plan will not be submitted independently, but will be part of a Stormwater Pollution Prevention Plan (SWPPP). Unless exempt, it will be approved with the SWPPP. Title information: Project title. Titles should be appropriate. It should be an erosion control plan, not a stormwater plan, or site plan, etc. In some cases a YV'PO package will contain a stormwater plan and a mitigation plan, but they should be on separate sheets with keys and page tities. Mitigation plans require a separate review and fee. Profcssional sea], with original signature and date for professionally prepared plans. Content: The erosion control plan must not contain information regarding permanent improvements that do not also appear on other plans. Erosion control plans are temporary documents that are discarded after projects are complete. Existing conditions plan view information: accurate current existing topography at the time of submittal, including all existing site features, and any recent disturbances, all at a legible scale date and source of the topographic information: All topography should be at least visually field verified by the designer within the last year WPO stream buffer limits; 100' from stream or contiguous wetland, 200-11 from reservoirs ' or floodplain limit if greater. No buffter disturbances without WPO Program Authority approval and a mitigation plan. floodplain limits (floodway and floodway fringe), including 100-yr flood limits for any channel with a drainage area of 50+ acres and floodplain designation. Floodplain undisturbed. Disturbances require a Special Use Permit or Floodplain Development Permit. Albemarle County Engineering E&SC Plan Checklist Page 2 of 4 all existing easements (access, drainage, sight, sanitary casements, etc.) with decd book references, locations and dimensions all critical slopes (typically shaded) 1'0— Zoning Ordinance buffers shown and protected undisturbed. Disturbances require Planning approval of a waiver. Proposed plan view information: GradV'g: proposed topography at minimum 2' contour intervals - tied into existing contours, as well as all proposed site features. (Sites with less than 6' of grade change should consider using smaller contour intervals.) These should agrize with other final plans. proposed slopes are all 2:1 (horizontal:vertical) or flattcr JDcsign Manual, Section 81 proposed slopes steeper than 3:1 have low maintenance (not grass) ground covcr ,,�specified on the plan 1 Design Manual. Section 8: %111 existing critical slopes are not disturbed, unless a waiver or exemption has been granted for the disturbance. [ 18-4.2. 14-3 )04] Retaining Wall Plans approved. Any walls supporting roads or necessary infrastructure an require engineered plans (not generic manufacturer's details) d computations. � Design Manual Section 9 1 This will also be required where walls are close to property lines and there is the danger of affecting neighboring property, either during construction, with later failures or with pedestrian or vehicle safety. final conto�� shapes and slopes ensure no undrained pockets or stagnant pools Narrative: narrative and project title (Narratives are now optional, and not reviewed by the County, other than noting whether they are not seriouly in error, like a boilerplate with another County's name on it) III oi cct descl I ption OXiS11111-1 SItC C011ditiollS ([C�Ci-ipl,1011 adjacent arcas description 01'I'MIC MCLU� LICSCI-il)11011 iiIJUL111W M)V 01Y-Si(C ilt-CUN 101- b0i-I'M\, %\ZNLC 01- 0[hel- diS(Lirbancc, SPCCi2l LNC permit For cut gicater th.ln �0,000cy in RA zoiling SOHS LIOSCIAIM101IS COLIAM' Ci-ON1011 C01111-01 11OWS slonliwatei runorl'consideranuils: this can rcl�er iL) the �tvriilwatcr inanaacment Plan sediment hasiti desion CORIJILIM601IN SU111111MA 601. each sedmicia basill sediment Irap desioll C011111LIL111 Oil A111111MI-V torcaclisedimen(Li-ap Eros - n and sediment control measures: limits of clearing and grading encompassing all disturbances, entrances, staging and parking areas, areas where sediment laden nmoff will cross, or any construction related activities. This must match anv landscapine and conservation Dians submitted with site plans a construction entrance (CE) draining to a sediment trap (ST) or sediment basin (SB) V- dust control symbols (DC) :z temporary and permanent seeding symbols (TS, PS) Albemarle County Engineering E&SC Plan Checklist Page 3 of 4 existing drainage divides existing vegetation, with trees to be saved located by drip lines. This must match any landscaping and conservation plans. protection Provided for all stazeslphase ofconstruction. from initial land clearinz to final -grades and hacdscaRes. This is our most important item. Plans which show only inlet protection on proposed drainage systems, which are only possible to install upon complet ion of grading, should be denied without further review. no erosion co trol measures in the way of construction access or jeradine. Diversion dikes or silt fence are not placed in the middle of the site, or through access or grading. Sediment traps are not under or on top of fill material or held up by retaining walls. Construction entrances are not on fill, etc. Grading cannot occur without perimeter controls. Ythe conceptfor site protection is not ad�quate in this regardfirther review of the plan may not be possible. existing soil boundaries are shown with labels. Areas already disturbed are indicated, with constructed fill depth or cut noted. critical erosion areas are identified; areas of constructed slopes, areas near property lines adjacent off -site disturbances are shown with erosion control facilities a stockpile location. where cut or fill balances have a 10,000 cubic yard deficit or more, plans should not be approved without a waste area identified. This must be on -site, or on another approved and permitted site. (Inspectors will confirin this during pre -construction meeting.) a staging and parking area, or other construction related areas diversion dikes are used to direct drainage to traps and basins silt fence is not used across contours in place of diversion dikes. silt fence is limited to areas of sheet flow with '/4acre per 100-11 of level on -grade silt fence. Plans showing only silt fence, without sediment trapping measures, should not be approved unless they meet this criteria and fill dirt is minimal. all swales and low points at theverimeter of the site have a sediment trap or basin. Silt fence in swales is typically not adequate. Check dams do not substitute for traps. If the conceptfor siteprotection is not adequate in this regard, firther review of theplan may not be possible. temporary slope drains (TSD) or diversions are provided to prevent discharge over disturbed or fill slopes inlet protection (IP) on all inlets t7 culvert inlet protection (CIP) on all culvert inlets outlet protection (OP) on all outlets all watercourses are protected and encroachments minimized stream crossing (USC, SC) and diversions are provided at all stream crossings. 1,L' adequate channels (MS-19) provided foTeach outfall (see Design Manual for minimum content) ' all traps and basins are shown with proposed contours. Simple boxes or symbols are not sufficient, in most cases, to determine layout or bond amounts. F .!�pch trap; drainage area is 3 acres or less —7� sized for total drainage area, including those for in -line upstream facilities L wet storage is 67 cy or more dry storage is 67 cy or more CZ—' wet storage is 4-11 deep or less Albemarle County Engineering E&SC Plan Checklist Page 4 of 4 wet storage side slope is 1: 1 or flatter dry storage side slope is 2:1 or flatter V�'4 stone weir is 6ft per acre of drainage area vl� embankment and stone weir height is 5-ft maximum from outside toe embankment top width is adequate (see table 16 reference) 2:1 length:width ratio for flow path For each basin; (GB 3.14) sized for total drainage area, including those for in -line upstream facilities wet storage is 67 cy or more dry storage is 67 cy or more wet storage side slope is 1: 1 or flatter dry storage side slope is 2:1 or flatter embankment 15' high or less from downstream toe — principle and emergency spillways sized per handbook requirements — embankment has P freeboard during 25-yr storm with emergency spillway — embankment has 2' freeboard during 25-yr storm without emergency spillway — trash rack / anti -vortex device specified per handbook requirements riser anchor size specified per floatation computation dewatering device sized for 6+hr drawdown of dry storage: 3" dia. minimum safety fence and signs stating "danger, quick sand, do not enter" provided if near any residential properties, or public access structures and embankment match permanent design for facilities to be converted to permanent stonnwater management facilities embankment top width is adequate (see Design Manual reference details) 2:1 length:width ratio for flow path. If necessary, baffles specified only on temporary structures (p.Ill-79). Baffles must extend to bottom of basins. Baffle design during construction is a hassle so should be properly dimensioned during design if possible. Details: t11*1 a paved construction entrance detail (see Design Manual reference details) for projects in the development areas over 10 acres V11, a typical section for each temporary channel or diversion, referenced from the plan sheets Existing ground should be shown at the maximum cross -slope on the plan. U/ detailsand copies of Program Authority permissions for any variances. Mas� or Early Grading: h 1AL Nrr mass grading Planning approval. (This is also called rough or early grading plans which contain only approximate finished grades and culverts necessary to grade) Mass grading can only be permitted within planned developments where a concept grading plan was approved with the rezoning. The agent (Director of Planning) needs to formally determine that the grading plan is in general conformity with the approved rezoning plan. Otherwise, an initial site plan needs to be approved prior to issuance of a grading permit. Issuance of a grading permit at the initial site plan stage, as apposed to after final plan approval, requires specific approval from the County Engineer.