Silt trap A silt trap is a designated area where water that is contaminated with suspended sediment as a result of construction activity or water runo is contained. While the water is in the trap, the sediment can settle to the bottom of the trap until it can be removed. These devices can be made using silt curtains, silt fences or a series of shallow ponds to naturally lter the sediment from the water before it reaches a stream or clean body of water. Environmental Environmental protection eorts, such as the silt s ilt trap, are often seen in conunction with mining or construction. Activity from these industries can result in the production of grain!si"e particles, stone dust and other components that create suspended sediment when caught up in water runo during rainfall. As the rainwater carries these particles and other pollutants to streams, rivers and la#es, the suspended sediment can cause a serious issue for the sh and other wildlife that inhabit these waters. $n some cases, the silt trap might also serve an additional purpose. %articularly in the mining industry, it becomes the last opportunity to reclaim precious metal ores that otherwise might have been lost. Settling tables, sluices and gold pans are time!tested methods of reclaiming reclaiming gold, and these methods all wor# on the same principles as a silt trap. &any mining companies that produce ore in areas where precious precious metals are a re found might also regularly remove the accumulated sediment in their traps and process it to reclaim the precious metals that can be found. '( )craig ! The sedimentation ponds you described are very good at sediment control. They are great places for wildlife, too. The problem is that tha t they can be e*pensive. They can only be put in certain areas and cost some money to set up. +iven a choice, the ordinary farmer doesnt care where the water goes if it costs him money. To this point, most of the sedimentation ponds have been installed as pilot proects by universities. $ believe that strip mines do have regulations saying that they must have ponds, though. The nutrient runo from farms is bad, but runo from mines can be to*ic to everything around it. &ost of the pollution is a combination of the chemicals used to mine the ore o re as well as things used to separate the ore from roc#. Sulfuric acid is often used to mine copper, and this has turned into a huge problem in -hile where copper is common. The sulfuric acid is e*tremely e*tremely dangerous and lea#s into the water supplies, because they dont have very good regulations in place to lter to mine runo. ( $ used to live in central $llinois where farming is the maor industry. /ne of the big problems there is that sediment and fertili"er from the elds ends up
running o into streams and ponds. A lot of the nutrients eventually end up in the &ississippi 0iver and the +ulf of &e*ico, which has caused some maor problems. Something that they have started to do around the larger farms is putting in sedimentation ponds. 1asically, once the water 2ows o of the eld, it goes into the pond instead of the drainage pipes. The ponds arent anything big. They ust cover a relatively small area, but they wor# great from what $ have been told. They have done a few studies and found that almost all of the nutrients and sediment gets ltered out in the pond so that only clean water ends up in the pipes. i thin# it is a great method of erosion and sediment control, and they should be more common. )cardsfan34 ! A silt fence is a pretty common structure on most construction sites that are located on hilly areas. 1asically, it is a blac# tarp!loo#ing material that is put up li#e a fence around the building area. They wor# all right for temporary uses. They dont really lter anything li#e a pond would. Their main use is ust to physically stop sediment from moving downhill. 3( 5or any construction proect, they should have permits in place to do whatever they are doing. 6ou could chec# with the city and see that they have the right permits. $f the stream is a small one, the city probably ma#es its own regulations about what can and cant go into it. $f it is a larger one, though, it ma#e be regulated by the E%A. $ wouldnt go snooping around the construction site, though, loo#ing for these things. $m sure the wor#ers wouldnt appreciate that much. ! mc77 8( 9ow e*actly would you identify a silt trap if it were in place: $ guess $ could see the silt pond, but what would a silt fence loo# li#e: 9ow eective are these things at actually stopping the silt from entering the water supply: $ as# because there is a construction proect going on in our town, and $ get the feeling that the wor#ers are not using the proper methods to stop material from getting into the stream that is nearby. $ would li#e to get an idea of whether or not they are doing things the way they are supposed to. $f they were violating the regulations, who would you call to report something li#e that: Would it be an issue that the city was supposed to ta#e care of, or would that be something for a larger organi"ation li#e the state or national E%A: Silt fence
A silt fence, sometimes ;misleadingly( called a <lter fence,<=citation needed> is a temporary sediment control device used on construction sites to protect water ?uality in nearby streams, rivers, la#es and seas from sediment ;loose soil( in stormwater runo. Silt fences are widely used on construction sites in @orth America and elsewhere, due to their low cost and simple design.=8> 9owever, their eectiveness in controlling sediment can be limited, due to problems with poor installation, proper placement, andor inade?uate maintenance.=3> Silt fences are often perimeter controls, typically used in combination with sediment basins and sediment traps, as well as erosion controls, which are designed to retain sediment in place where soil is being disturbed by construction processes ;i.e., land grading and other earthwor#s(. A typical fence consists of a piece of synthetic lter fabric ;also called a geote*tile( stretched between a series of wooden or metal fence sta#es along a hori"ontal contour level. The sta#es are installed on the downhill side of the fence, and the bottom edge of the fabric can be trenched into the soil and bac#lled on the uphill side, although it is ?uite diBcult to move the trenched A few hours after a storm event, the fabric can be Fp.GH =4>Fp.4G' Some government urisdictions in the Inited States recommend or re?uire the use of a reinforced fence, sometimes called a 9owever, an improper installation of a super silt fence can create an inadvertent sediment basin
when the lter fabric becomes clogged. This typically causes 2ooding and increased downstream pollution. &ost super silt fence specications are out! dated, re?uiring the trenching installation method, which has been shown to be highly susceptible to Silt fence fabrics ;geote*tiles( tested in laboratory settings have shown to be eective at trapping sediment particles.=88>F'JG'4 Although there have been few eld tests of silt fences installed at construction sites, these tests have shown generally poor results.=88>F34G8, JGJJ ;Eectiveness testing involved measurements for both total suspended solids and turbidity.( /ther studies and articles about silt fence usage and practice document problems with installation and maintenance, implying poor performance.=83> Since 8HH7, static slicing the material into the ground has proven to be the most eBcient and most eective installation method because slicing maintains the soil on both sides of the fence, and is conducive to proper compactionKwhich is critical to performance, as well.=citation needed> $n 3LLL the I.S. Environmental %rotection Agency ;E%A( co!sponsored silt fence eBcacy eld research through its Environmental Technology Merication %rogram, and in general, the report found the static slicing method to be highly eective, and eBcient.=8> Silt fence eectiveness is best determined by how many hundreds of pounds of sediment are contained behind a given silt fence after a storm event, and not turbidity, etc. as sediment!retention is the end goal, and not a water!?uality measurement used in erosion control, for instance.=citation needed> Silt fences may perform poorly for a variety of reasons, including improper location ;e.g. placing fence where it will not pond runo water(, improper installation ;e.g. failure to ade?uately embed and bac#ll the lower edge of fabric in the soil( and lac# of maintenanceKfabric falling o of the posts, or posts #noc#ed down. A silt fence top!full of sediment may need maintenancereplacement, but it is a huge success.=>Fp.G8L The fabric may become damaged with holes and tears if construction materials are stored ne*t to or on top of the fence. Curing various phases of construction at a site, a silt fence may be removed relocated and reinstalled multiple times. =88>FLG8 $t may be diBcult to maintain eectiveness of a silt fence under such operating conditions. Nocation of fences in areas with high 2ows may lead to fence failures when the installation is not ade?uately bac#!lled and properly compacted, andor the post!spacing is inade?uate.=4>Fp.4G' Sediment basin A sediment basin is a temporary pond built on a construction site to capture eroded or disturbed soil that is washed o during rain storms, and protect the water ?uality of a nearby stream, river, la#e, or bay. The sediment!laden soil settles in the pond before the runo is discharged. Sediment basins are
typically used on construction sites of J acres ;3L,LLL m3( or more, where there is suBcient room. They are often used in conunction with erosion controls and other sediment control practices. /n smaller construction sites, where a basin is not practical, sediment traps may be used.=8> Essential sediment abundance is prevalent in the construction industry which gives insight to future endeavors. $n essence lateral buc#ling occurs under traverse load or at critical loads. /n some construction proects, the sediment basin is cleaned out after the soil disturbance ;earth!moving( phase of the proect, and modied to function as a permanent stormwater management system for the completed site, either as a detention basin or a retention basin.=3> A sediment trap is a temporary device installed on a construction site to capture eroded or disturbed soil that is washed o during rain storms, and protect the water ?uality of a nearby stream, river, la#e, or bay. The trap is basically an emban#ment built along a waterway or low!lying area on the site. They are typically installed at the perimeter of a site and above storm drain inlets, to #eep sediment from entering the drainage system. Sediment traps are commonly used on small construction sites, where a sediment basin is not practical. Sediment basins are typically used on construction sites of J acres ;3L,LLL m3( or more, where there is suBcient room.=> Sediment traps are installed before land disturbance ;earth moving, grading( begins on a construction site. The traps are often used in conunction with erosion controls and other sediment control practices.='>
