Pollution control methods pdf Land Disturbance Inspection Record is also available as a pdf. 7 Construction Inspection Guidance for Sec.
Providing for the control of both sheet and gully erosion is a necessary part of any highway project. This article and EPG 611 Embankment Protection are concerned with methods and criteria for the control of sediments from sheet erosion during and after construction activites. Provisions of the federal clean water act and related state rules and regulations require stormwater permits where construction activities disturb greater than one acre over the life of a project as part of a common plan or sale. MoDOT to accomplish road construction activities. Contract plans shall include erosion control measures that are sufficient to protect streams, lakes and private land adjacent to MoDOT right of way. Temporary and permanent water pollution control measures shall be included in design plans so that contractors can develop appropriate bids. Control of water pollution will be accomplished through the use of berms, slope drains, ditch checks, sediment basins, seeding and mulching, straw bales, silt fences, and other erosion control devices or methods.
Temporary erosion control measures shall be coordinated with permanent erosion control measures to assure economical, effective and continuous erosion control. Rock ditch checks are the predominant ditch check to be used. Rock ditch checks have an 18 in. Alternate ditch checks have a nominal effective height of 9 in. Alternate ditch checks are specified where drainage areas are 3 acres or less, ditch slopes are 4 percent or less and expected ditch flow volumes are small. Rock ditch checks are specified in most drainage areas where ditch slopes are 10 percent or less and expected ditch flow volumes are high, or in locations where the project is in close proximity to streams or other sensitive areas.
Experience and history have shown that Rock ditch checks perform much better than Alternate ditch checks and seldom need to be replaced. For this reason a system of Rock ditch checks, although more expensive than Alternate ditch checks at installation, will often prove to be the less expensive over the life of the project considering the cost of unpredictable storm damage to Alternate devices. An estimate of the required number of ditch checks based on a height of 24 in. Use of a silt fence consists of furnishing, installing, maintaining, and removing a geotextile barrier fence designed to remove suspended particles from water passing through the fence.
Materials used for silt fences must meet certain requirements. Silt fencing is most effective to control sheet erosion along the edge of the right of way where runoff from erodible fill attempts to leave the project onto the adjacent property or into an adjacent stream. Silt fence is never used to cross a ditch, stream or drainage channel, and in no case installed perpendicular to, or downgrade from a pipe or culvert. Likewise, silt fence is never used to protect drop inlets.
A temporary berm is a temporary ridge of compacted soil, with or without a shallow ditch, constructed at the top of fill slopes or transverse to centerline on fills. The purpose of these ridges is to divert storm runoff from small areas away from steep slopes and direct this water to temporary outlets where the water can be discharged with minimum slope erosion. Temporary slope drains are required on fill slopes at approximately 500-foot intervals or as directed by the engineer. This work shall consist of preparing and fertilizing a seedbed, furnishing and sowing of seed, and mulching. The purpose of temporary seeding and mulching is to produce a quick ground cover to reduce erosion in disturbed areas that are expected to be redisturbed at a later date. If the project is to be done in stages and it is known that areas will be shut down for a significant amount of time, designers are to include this cost so that contractors can bid accordingly.
A temporary pipe is a conduit used temporarily to carry water under a haul road, silt fence, etc. It is used to convey normal and expected high flows at temporary stream crossings, preventing the contractor’s equipment from coming in direct contact with the water when crossing active streams or intermittent streams created during heavy rainfalls. A temporary sediment basin is an excavated or dammed storage area that is used for short-term erosion control purposes. These structures should be installed prior to land distrubance activities. They will be constructed with available grading equipment at locations shown on the contract plans.
They are commonly used prior to the installation of more permanent, designed erosion controls. Where the use of a sediment basin of sufficient size as described above is impractical, other similarly effective BMP’s, such as a sediment trap, must be employed to prevent sediment from leaving MoDOT right of way. The location of sediment traps will be shown on the plans. A sediment trap is a structure constructed of rock or other non-earthen material sufficient to impound water. It is placed down grade of a drainage structure outlet to prevent sediment from leaving MoDOT right of way. In larger, more permanent streams, they will be placed parallel to the stream at each drainage ditch outlet. A sediment trap will be constructed in accordance with Standard Plan 806.
Quantities for sediment removal are estimated using 1 yd3 per ditch check, 1 yd3 per 100 linear ft. Sediment basins are constructed to trap and store sediment from erodible areas in order to protect properties and stream channels below the installation from excessive siltation. These structures trap and store sediment that may not be caught by upgrade temporary erosion control measures. If right of way is available, a well-placed sediment basin can negate the need for other temporary controls in the drainage area upgrade from the sediment basin. A rock dam is an oversized Type II rock ditch check that serves to impound water and sediment. It is usually is installed down grade from a culvert outlet or at locations where drainages exit MoDOT right of way. Rock dams are not appropriate where impounded sediment and gravel could accumulate inside of the culvert.
Section 404 of the Clean Water Act. In these cases, rock dams are to be placed at the ditch outlets, parallel to the stream . As with sediment basins, if right of way is available, a well-placed rock dam can negate the need for other temporary controls in the drainage area upgrade from the structure. Type C berms are specified at the toes of spill slopes around bridge construction operations and will be constructed to the specified dimension.
It is important that the contract plans show the general presence of a type C berm so contractors may bid accordingly. However, the actual precise location of the structure can only be determined at the time of installation and shall be field fit at the direction of the engineer. Such diversions will enable the establishment of permanent vegetative cover and will reduce the likelihood of gully formation. Erosion of sideslopes at the end of bridges just beyond the end of the bridge wing walls is managed by installing bridge approach slabs with curbs to direct roadway and bridge drainage away from the bridge end. Drain flume are constructed using a Type I Rock Ditch Liner and permanent erosion control geotextile fabric. Temporary erosion controls must be kept in place and maintained until revegetation has occurred to an extent sufficient to prohibit the formation of gullies by runoff.