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Home My WebLink AboutSW5230802_Plansheet - Misc. Detail_20231222 (3) ..J OUTLET PROTECTION DETAILS 5" PVC Outlet Pipe from Basin z SKIMMER BASIN DETAIL w Attach rope to skimmer for maintenance. d- 0, 1.5 ft. � Class B 1' Freeboard Embankment Erosion Control Stone Bo f fles O O (Extend 4 ft. laterally 6"PVC 1 Past Bottom of Basin Sloe 4 r si ❑ e s•� ft• ��° ST�� p ) Tic e = 22 ov°o F°°>o ; co O = U o I = Dewaterin e ATTACH SILT/FILTER BAG. zone " min. jnVert levation of emercgencyspitlway (SEE DETAIL SHEET 8) 6ft Filter fabric - - -0. .� .� � 1.0 ft, E$elhivanCy P Y Maintenance Considerations Inspect outlet protection structures weekly and after significant (112" or greater) Sediment Stone Pad for miner Storage zone Cross-Section (4'x4'1'high) rainfall events to see if any erasion around or below the riprap has taken place, View or if stones have been dislodged. Immediately make all needed repairs to prevent further damage. EMBANKMENT WIDTH: 10 FT. SIDE SLOPES SHALL BE 3:1 (H:V) w Proposed Skimmer Basin Calculations Skimmer Basin Construction Specifications z z Q Design Elevations ft. EL 1.Clear,grub,and strip the area under the embankment of all vegetation and root mat. O W Surface Area at normal pool, Basin Dimensions, ft. Basin Dimensions, ft. Inlet Outlet Remove all surface soil containing high amounts of organic matter and stockpile or Uq Q Inflow square ft, (at Second Spillway) At Base of Basin Storage Volume, Cubic Ft. Skimmer Draw Down Invert of TO of Crest of TO of dispose o€it properly.Haul all objectionable material to the designated disposal area. Watershed Weighted q �' p Y} ( ) Area g Invert of p P 10-yr 24-hr 25-yr 24-hr p p p y- � � p Q Area Average Te, i Disturbed, Time, hours Secondary Berm Place temporary sediment control measures below basin as needed. Q J Basin g Q cfs O (2) Orifice, Horizontal Horizontal Riser Storm Elev. Storm Elev. Re uired Provided Length Width Length Width acre Required Provided Pipe(3) Pipe(3) Spillway 2.Ensure that fill material for the embankment is free of roots,woody vegetation,organic 111 Q (acres) CN minutes i o° q g q inches 1 9.76 68 12.6 27.49 8,934 11,174 140 70 118 50 2.36 4,248 31,582 3 79.8 612.00 611.70 NIA 615.50 617.00 615.74 616.08 matter,and other objectionable material.Place the fill in lifts not to exceed 9 inches,and Z Q machine compact it.Over fill the embankment 6 inches to allow for settlement. 3.Shape the basin to the specified dimensions.Prevent the skimming device from settling Q Q (1) Required Surface Area is based on 325 sf per cfs of 010 peak inflow into the mud by excavating a shallow pit under the skimmer or providing a low support Q Q (2) Required Volume is based on 1800 cf/ac. of disturbed area under the skimmer of stone or timber. U Note: Baffle Spacing shall be every 35 ft. 4.Place the barrel(6-inch Sched.40 PVC pipe)on afirm,smooth foundation of impervious soil,Do not use pervious material such as sand,gravel,or crushed stone Note: Bottom 1 ft. is for sediment storage and is not included in volume calculations around the pipe.Place the fill material around the pipe spillway in 4-inch layers and compact it under and around the pipe to at least the same density as the adjacent embankment.Care must be taken not to raise the pipe from the firm contact with its foundation when compacting under the pipe haunches. 5.Assemble the skimmer following the manufacturer's instructions. z 6.Lay the assembled skimmer on a 4'x4'xl'high stone pad with the flexible joint at the Q W CROSS-SECTION BAFFLE (NTS) inlet the barrel pipe.Attach the flexible taint to the barrel pipe and position the skimmer Uer over the stone pad.Be sure to a ttach a rope to the skimmer and anchor it � U to the side of the basin.This will be used to pull the skimmer to the side for maintenance. Q Q J 7.Earthen Spillways-Install the spillway in undisturbed soil to the greatest extent I— possible.The spillway should be lined with laminated plastic or impermeable geotextile m — \ J Support Post,24'into Stake to support wire fabric.The fabric must be wide and long enough to cover the bottom and sides and Q bottom or side extend onto the top of the dam for anchoring in a trench.The edges may be secured with = Q 8-inch staples or pins.The fabric must be long enough to extend down the slope and exit W onto stable ground.The width of the fabric must be one piece,not joined or spliced; W p SECONDARY SPILLWAY otherwise water can get under the fabric.If the length of the fabric et insufficient for the = entire length of the spillway,multiple sections,spanning the complete width,may be Q Support e a to wire used.The upper section(s)should overlap the lower section(s)so that water cannot flow to prevent sagging under the fabric.Secure the upper edge and sides of the fabric in a trench with staples or Q pins. = Coir mesh or similar,stapled or Q Q trenched into bottom or side 8.Inlets-Discharge water into the basin in a manner to prevent erosion.Ensure that the = z < 44 diversion berms will have positive drainage to the upper end of the basin. U U Coir Fiber Mat Specifications4.Erosion Control-Construct the structure so that the disturbed area is minimized.Divert Q Porous Baffle Specifications p 1 J 10t 1 1 .51 surface water away from bare areas.Complete the embankment before the area is cleared. Stabilize the emerge ncy spi€lway embankment and all other disturbed ar eas above the Thickness:0.30 in.minimum I. Grade the basin so that the bottom is at equal elevation. Tensile Strength: 1348x 626 if/ft minimum centers. 2. Steel posts shall be driven to at least 24 inches below ground surface and spaced at 4 f Elongation:34%x 38%maximum Laminated Plastic Lining or Basin Maintenance t. Flexibility(mg-cm):65030 x 29590 b 3. Top of Fabric shall be at least 6 inches above stone spillway elevation and 2 inches lower than Flow velocity:Observed i 1 ft/see Impermeable Geotextile Fabric z berm elevation. Size fi 6 0 164 fi 120 SY) Inspect skimmer sediment basins at least weekly and after each significant (one half inch W 4. Bottom and sides of fabric shall be anchored in a 6 inch trench of pinned with S inch long erosion "C"Factor:0.002 control mattingstaples. n Area measured 50% or eater rainfall event and repair immediate) Remove sediment and restore the basin P � (measured): � P Y• 1GO%cocount fiber(coir)twine woven into high strength matrix M S. The baffles shall be composed of coin fiber matting with the following specifications. to its original dimensions when sediment accumulates to one-half the height of the first N Note:Porous baffles are to be tied back into basin embankments at bottom and sides of the weir. baffle. Pull the skimmer to one side so that the sediment underneath it can be excavated. Excavate the sediment from the entire basin, not just around the skimmer or the first cell. 0 Q (D o Z Make sure vegetation growing in the bottom of the basin does not hold down the ct skimmer. > � U SKIMMER DETAIL Repair the baffles if they are damaged. Re -anchor the baffles if water is flowing W 0 o I +; vs underneath or around them. U U � UQ Arrn Assembly 00 � z r\ � � Cn If the skimmer is clogged with trash and there is water in the basin, usually jerking on the W Q a a ; Q T' ° C"Enclosure rope will make the skimmer bob up and down and dislodge the debris and restore flow. If U C)o �., -C� q., N o this does not work, pull the skimmer over to the side of t he basin and remove the debris. U Z O ct o 7 PERSPECTIVE VIEW Water Unit Also check the orifice inside the skimmer to see if it is clogged; if so remove the debris. z LL o 0 7 PVC End PVC Elbow PVPipera 5chedule 40 U Cap PVC Pipe If the skimmer arm or barrel pipe is clogged, the orifice can be removed and the W ater ur ace obstruction cleared with a plumber's snake or by flushing with water. Be sure and replace PVC pod W the orifice before repositioning the skimmer. Schedule 40 PVC Tee V Holes in Pepe PVL Pipe PVC Tee Orifice Check the fabric lined spillway for damage and make any re quired repairs with fabric that (� H Underside Rexible Plate Hale spans the full width of the spillway. Check the embank ment, spillways, and outlet for Z �I erosion damage, and inspect the embankment for piping and settlement. Make all W Q a Bottom Surface necessary repairs immediately. Remove all trash and other debris from the skimmer and w Q EN❑ VIEW FRONT VIEW pool areas. [� C/ r'