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HomeMy WebLinkAboutWPO201600012 Checklist 2016-02-23Albemarle County Engineering Drainage Plan checklist for plan reviewers Updated 1 Dec 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, {Curved 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 computation packages where are separate from sealed plans. Drainage: [18-32.6.2d, 14-305,311] drainage area maps (This is a basic element, and without this there is no review) drainage computations (usually in the form of tables from the VDOT Drainage Manual App. 913-1 LD -2014, App.713-1 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 [14- 410] site runoff and entrances do not drain into streets (from VDOT Drainage Manual 9.4.5.2, 9.4.6.2) concentrated runoff (1 cfs or greater) does not run across travelways/streets (as above following VDOT design) drainage does not run across, through, or backwater in dumpster areas [18-4.12.19] 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. {Policy} 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) labels on all drainage structures provided (and should match the drainage computations and profiles) N provisions and easements 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 {Policy} Drainage profiles: (applicable to site plans, road and drainage plans) [14-311, 18-32] drainage profilesfor each pipe, structure or channel must 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 �� a label on each structure to correspond with the computations Albemarle County Engineering Drainage Plan Checklist Page 2 of 2 material and strength class or gage of each pipe manhole access every 300' for 15"42" or 800' for 48" or greater pipe slopes at 0.5% min. to 16% max. (per VDOT stnds for anchors over 16%) concrete inlet shaping (IS -1) specified on any structure with a 4' or greater drop safety slabs (SL -1) in any structure taller than 12'. top or rim elevation for each structure all invert elevations for each structure (with positive flow drop between inverts).Nb(oA4a f s4,v-A,4- i end sections (ES -1) or endwalls (EW -1) on all pipe outlets. Endwalls for culverts 48" or taller scour outlet protection at all outlets, corresponding to computations (Green Brook, OP) Drainage computations: (applicable to any plan proposing pipes, channels, etc.) Pipe computations for all pipes All 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 L> its There are no excessive outlet velocities (> 15fps) Curb inlet computations for any curb inlets on grade ,4/q All spreads are less than 10' carryover is accounted for �� 100% capture at entrances so no flow runs out entrances into travel lanes 100% capture, or overland flow of capacity storm, to stormwater management facilities. Typically stormwater management is designed to the l0year storm, and inlets on grade often cannot capture this. Inlets in sumps should be used. Curb inlet computations for any curb inlets in sump conditions G IA All flow depths are below 6" in the capacity table ARAll spreads are less than 10' 100% capture to stormwater management facilities D�i"cch computations for any ditches ,/ ditch linings specified per plans meet velocity requirements Culvert computations for any culverts _,i headwaters < 1.5 x culvert height, and 18" below shoulder elevation of streets. Outlet protection computations for all outlets / ,/ dimensions and stone sizes for all outfalls Proposed 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 _,Z 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 Updated 1 Dec 2014 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 Erosions and Sediment Control Handbook. Reference key; [Square Brackets] are County Code references, {Curved Brackets) are policy references, and (regular parenthesis) are explanatory. Links to reference documents are provided where possible. Application information: Z Completed WPO application and fees, with owners signature [County Code 18-32.4.3.2, 18-32.3.9, 17 Article II] Erosion Control plans require a Water Protection Ordinance ,(WPO) application and original owner's signature. No review is provided without application, owner signature and fees. This is true even for revisions. It is important that the owner be aware of comments and re -submittals, and this is the county assurance. /T Copies of federal and state permits for any wetland or stream disturbance. (Army Corps, VDEQ, etc) [17-604, 18-32.1.2, 14-311] VSP: 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 stonnwater plan, or site plan, etc. In some cases a WPO package will contain a stormwater plan and a mitigation plan, but they should be on separate sheets with keys and page titles. Professional seal, 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 pians 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. Adequate erosion control cannot be designed without accurate topography and drainage areas. -4A WPO buffer limits; 100' from stream or wetland bank, 200' from reservoirs, or floodplain limit if greater. No buffer disturbances without WPO Program Authority approval and a mitigation plan. floodplain limits, including I00yr flood limits for any channel with a drainage area of 50+ acres. Albemarle County Engineering E&SC Plan Checldist Page 2 of 4 Floodplain undisturbed. Disturbances require a Special Use Permit or Floodplain Development Permit. � all existing easements (access, drainage, sight, sanitary easements, etc.) with deed book references, locations and dimensions 1411 ,0,,v44- all 0,,44 -all critical slopes (typically shaded) / Zoning Ordinance buffers shown and protected undisturbed. Disturbances require Planning approval of a waiver. Proposed plan view information: Grading: proposed topography at minimum 2' contour intervals — tied into existing contours, as well as all proposed site features in later phases. (Sites with less than 6' of grade change should consider using smaller contour intervals.) These should agree with other final plans. proposed slopes are all 2:1 (horizontal:vertical) or flatter {Design Manual, section 81 Z proposed slopes steeper than 3:1 have low maintenance (not grass) ground cover specified on the plan {Design Manual, Section 81 existing critical slopes are not disturbed, unless a waiver or exemption has been granted for the disturbance. [18-4.2, 14-304] Retaining Wall Plans approved. Any walls supporting roads or necessary infrastructure require engineered plans (not generic manufacturer's details) and computations. {Design Manual, section 81 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 contour shapes and slopes ensure no un -drained 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 seriously in error, like a boilerplate with another County's name on it.) project description existing site conditions description adjacent areas description off --site areas description including any off-site areas for borrow, waste or other disturbance. A special use permit for cut greater than 50,OOOcy in RA zoning soils descriptions County erosion control notes stoimwater runoff considerations: this can refer to the stolmwater management plan sediment basin design computations summary for each sediment basin sediment trap design computation summary for each sediment trap Erosion and sediment control measures: limits of clearing and grading encompassing all disturbances, entrances, staging and parking areas, areas where sediment laden runoff will cross, or any construction related activities. This must match anv landscapinz and conservation plans submitted with site plans Albemarle County Engineering E&SC Plan Checklist / Page 3 of 4 a construction entrance (CE) draining to a sediment trap or basin dust control symbols (DC) temporary and permanent seeding symbols (TS, PS) 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 stages/phases of construction, from initial land clearing to final grades and hardscapes. This is our most important item. Plans which show only inlet protection on proposed drainage systems, which are only possible to install upon completion of grading, may be denied without further review. no erosion control measures in the way of construction access or grading. 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. If the concept for site protection is not / adequate in this regard, further 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. 4A 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. (Don't make the inspectors chase trucks to find the dump site violation.) 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 1/4 acre per 1 00f 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 the perimeter of the site have a sediment trap or basin. Silt fence in swales is typically not adequate. Check dams do not substitute for traps. Diversions which travel more than 10011, or go in and out of swales, are usually not maintainable in the field. If the concept for site protection is not adequate in this regard, further review of the plan 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 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. adequate channels (MS -19) provided for each 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. For each trap; drainage area is 3 acres or less Albemarle County Engineering E&SC Plan Checklist Page 4 of 4 Zsized for total drainage area, including those for in-line upstream facilities Z wet storage is 67cy or more dry storage is 67cy or more wet storage is 4' deep or less wet storage side slope is 1:1 or flatter dry storage side slope is 2:1 or flatter stone weir is 6ft per acre of drainage area embankment and stone weir height is 5' 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) ,A11A sized for total drainage area, including.those for in-line upstream facilities wet storage is 67cy or more dry storage is 67yr or more wet storage side slope is 1:1 or flatter dry storage side slope is 2:1 or flatter embanlanent 15' high or less from downstream toe principle and emergency spillways sized per handbook requirements embankment has 1' freeboard during 25yr storm with emergency spillway embankment has 2' freeboard during 25yr 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: T'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 stormwater management facilities embankment top width is adequate (see Design Manual reference details) 2:1 length:width ratio for flow path. Baffles specified only on temporary structures (p.III-79). Baffles are a big hassle in construction, and should not substitute for properly dimensioned design if at all possible. Details: a paved construction entrance detail (see Design Manual reference details) for projects in the development areas over 10 acres 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. details and copies of Program Authority permissions for any variances. Mass or Early Grading: !T 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.