806.8 Storm Water Pollution Prevention Plan (SWPPP)

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Additional Information

Land Disturbance Workshop 2010

806.8.1 Storm Water Permit and Storm Water Polution Prevention Plan (SWPPP)

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 has a general State Operating Permit, obtained from the Missouri Department of Natural Resources (DNR), that allows road construction activities and the associated land disturbance. The permit stipulates that MoDOT will follow certain erosion control guidelines and install temporary erosion control measures. Locally sponsored federal aid projects that are performed on MoDOT right of way and are using MoDOT’s land disturbance permit are required to comply with MoDOT Standard Specifications, and therefore, must follow this Storm Water Pollution Prevention Plan (SWPPP). Cities, counties and other government entities may already possess their own State Operating Permit and, in that case, must comply with their own SWPPP.

In a few rare cases, MoDOT may require contractors to obtain their own individual State Operating Permit for land disturbance activities even though the project is being constructed on MoDOT right of way. These unique situations will normally be design/build projects that are funded by MoDOT, but totally managed by the contractor. MoDOT will coordinate with DNR whenever one of these design/build projects commences.

The purpose of the SWPPP is to ensure the design, implementation, management and maintenance of Best Management Practices (BMPs) in order to reduce the amount of sediment and other pollutants in storm water discharges associated with the land disturbance activities; comply with the Missouri Water Quality Standards, and ensure compliance with the terms and conditions of the general permit.

The following documents were used in the preparation of this SWPPP:

• Best Management Practices for Erosion and Sediment Control, (Report No. FHWA-FLP-94-005) published by the United States Department of Transportation (1995)
• Storm Water Management for Construction Activities: Developing Pollution Prevention Plans and Best Management Practices, (Document number EPA 832-R-92-005) published by the United States Environmental Protection Agency (1992)
• Protecting Water Quality: A field guide to erosion, sediment and storm water best management practices for development sites in Missouri
• Missouri Standard Specifications for Highway Construction
• Missouri Department of Transportation Engineering Policy Guide
• Menu of BMPs – United States Environmental Protection Agency.

806.8.2 Site Description

The Engineering Policy Guide article EPG 237.1 Plan Details describes the information that is to be included in all plans that are used by contractors to build highways. All highway and bridge projects are constructed from a set of design plans that are generated by MoDOT designers or consultants. The plans show all existing topographic features, buildings, roadways and drainages, as well as right of way limits.

The plans contain sufficient information to be of practical use to contractors and site construction workers to guide the installation of BMPs in the interim and final stages of construction. A set of final plans is always on location at active MoDOT job sites, usually in the possession of MoDOT’s construction inspector or the contractor superintendent. In the early stages of construction these final plans will usually include hand written notes showing the locations of temporary BMPs.

Contract plans shall include erosion control measures that are sufficient to protect streams, lakes and private land adjacent to MoDOT right of way, and the location of most of these controls will be depicted on the plan sheets. Temporary erosion control measures shall be coordinated with permanent erosion control measures to assure economical, effective and continuous erosion control. Construction of permanent erosion control measures that may contribute to the control of siltation, shall be accomplished at the earliest practicable time.

806.8.3 Drainage Areas

In compliance with the Missouri Clean Water Law (Section 644.051), neither MoDOT nor MoDOT's contractors shall pollute any waters of the state, or place, cause, or permit to be placed any water contaminant in a location where it is reasonably certain to cause pollution of any waters of the state. Also, they shall not discharge water contaminants into any waters of the state, which reduce the quality of these waters below the state's water quality standards. These water quality standards include the following (MO 10 CSR 20-7):

(a) Waters shall be free from substances in sufficient amounts to cause the formation of putrescent, unsightly or harmful bottom deposits or prevent full maintenance of beneficial uses.

(b) Waters shall be free from oil, scum and floating debris in sufficient amounts to be unsightly or prevent full maintenance of beneficial uses.

(c) Waters shall be free from substances in sufficient amounts to cause unsightly color or turbidity, offensive odor or prevent full maintenance of beneficial uses.

(d) Waters shall be free from substances or conditions in sufficient amounts to result in toxicity to human, animal or aquatic life.

(e) Waters shall be free from physical, chemical or hydrologic changes that would impair the natural biological community.

(f) Waters shall be free from used tires, car bodies, appliances, demolition debris, used vehicles or equipment and solid waste as defined in Missouri’s Solid Waste Law, Section 260.200, RSMo, except as the use of such materials is specifically permitted pursuant to Section 260.200–260.247.

MoDOT personnel or contractors hired by MoDOT shall comply with these and any other federal, state, and local laws and regulations controlling pollution of the environment. To ensure that these general criteria are met, the following guidelines will be observed:

1) Machinery shall be kept out of the waterway as much as possible.

2) Fuel, lubricants, debris and other water contaminants shall not be stored in areas that are subject to contact with water (such as adjacent to stream banks) or where contaminated runoff from the storage areas can enter waters.

3) Refueling and maintenance (e.g., oil changing) of machinery shall not take place in, or directly alongside, any water body.

4) Clearing of vegetation/trees shall be kept to the minimum required to accomplish the activity.

5) Riparian areas and banks shall be restored to a stable condition through recontouring and revegetation of the area, as necessary, as soon as possible (normally within three working days of final contouring).

6) Work shall be conducted during low flow whenever possible.

7) Wetland areas shall be avoided to the extent practical.

8) Work shall conform to all conditions that are part of the USACOE Section 404 permit and the ancillary MDNR Section 401 Water Quality Certification.

EPG 127.19 Section 404 Clean Water Act for Bridge Demolitions provides a detailed explanation of the process that is followed whenever a stream or drainage channel may fall into USACOE jurisdiction.

806.8.4 Temporary Erosion and Sediment Control (MO Specifications Division 800)

Temporary water pollution control measures shall be required of all contractors MoDOT hires. The contractor shall exercise best management practices throughout the project to control water pollution. Construction of permanent drainage facilities and other activities, which may contribute to the control of siltation, shall be accomplished at the earliest practicable time. This work shall consist of furnishing, installing, maintaining, and removing temporary control measures as shown on the plans (see MoDOT Standard Plan 806.10) or as ordered by the engineer. The 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. Pollutants such as chemicals, fuels, lubricants, bitumens, raw sewage or other harmful materials shall not be discharged from the project. No work shall be started until the erosion control timetable and methods of operation have been approved.

Temporary erosion control measures shall be coordinated with permanent erosion control measures to assure economical, effective and continuous erosion control. 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.

The engineer shall routinely inspect the condition of erosion controls and shall notify the contractor within 24 hours if any controls are found to be in disrepair or are not functioning at the desired level of effectiveness. Inspections are to be conducted at a frequency of once every seven days. Additional post-rainfall inspections will commence within 48 hours following significant rainfall. Significant rainfall means an event that causes linear flow in ditches and the subsequent overtopping or potential damage to BMPs. If sediment control devices at outfall locations have overtopped (denoting runoff), an inspection report will be completed. If rainfall is not sufficient to cause runoff, inspection reports may not be completed until the next scheduled 7-day inspection. The inspector will ensure that rainfall measurements are made on the job site and routinely monitor weather forecasts. Directives to the contractor shall be noted in the inspector's diary, which shall be available for review by DNR upon request.

Materials required for erosion control measures shall meet the standards of the following Missouri Standard Specifications for Highway Construction sections:

Name of Material	Sec
Fertilizer and Lime	801
Straw for Bales	802
Mulching, rates and material	802
Seed	805
Geotextile Fabric	624 & 1011

806.8.4.1 Construction Requirements

The engineer may limit the surface area of erodible earth material exposed by clearing and grubbing, or excavation, borrow, and fill operations, and may direct the contractor to provide immediate permanent or temporary erosion control measures to prevent contamination of adjacent streams or other watercourses, wetlands, lakes, ponds, and other water impoundments. Such work may involve the construction of temporary berms, dikes, dams, sediment basins, slope drains, and the use of temporary seeding and mulching, or other erosion control devices or methods as necessary.

The contractor shall be required to incorporate all permanent erosion control measures into the project at the earliest practicable time. Temporary erosion control measures shall be used to correct conditions that develop during construction which were not foreseen during the design stage. Temporary erosion control shall also be used when needed prior to installation of permanent erosion control measures or when needed temporarily to control erosion that develops during normal construction practices, but are not associated with permanent control measures on the project.

Clearing and grubbing operations shall be scheduled and performed so that grading operations and temporary and permanent erosion control measures will follow immediately thereafter. The surface area of erodible earth material exposed at one time by clearing and grubbing, by excavating, by fill, or by borrow, shall be minimized to prevent runoff. The engineer may limit the total acreage of erodible earth material to be exposed at one time as determined by an analysis of project conditions. In such cases the engineer will identify specific BMPs and controls that have been, or will be installed in order to exceed the specified maximum disturbed acreage threshold.

The engineer will limit the area of clearing and grubbing, excavation, borrow and embankment operations in progress commensurate with the contractor's ability to keep the finish grading, mulching, seeding and other erosion control measures current. Should seasonal limitations make such coordination unrealistic, temporary erosion control measures shall be implemented as directed by the engineer.

Unless otherwise approved, construction operations in rivers, streams, wetlands and impoundments shall be restricted to those areas that must be entered for the construction of temporary or permanent structures. Rivers, streams, wetlands and impoundments shall be promptly cleared of all falsework, piling, debris or other obstructions placed therein or caused by the construction operations.

Frequent fording of live streams or wetlands with construction equipment is not permitted. Temporary bridges or other structures shall be used wherever an appreciable number of stream crossings are necessary. All temporary fills and structures placed in streams, wetlands, or impoundments will be removed and the site returned to natural or intended contours prior to completion of construction. Unless otherwise approved, mechanized equipment shall not be operated in live streams except as may be required to construct channel changes and temporary or permanent structures. If a Section 404 permit is applicable for a project, its requirements and/or conditions shall be followed.

Site-specific erosion controls above and beyond MoDOT standard specifications shall be discussed with the contractor at a preconstruction conference. Special conditions may be developed which can include limitations on the amount of surface area that can remain unprotected at one time or special water quality or stream protections requirements.

The location of all local material pits (other than commercially operated sources) and all excess material areas shall be subject to the approval of the engineer (material in this case refers to soil and rock). Construction operations shall be conducted and pollution control measures implemented so that erosion will not result in water pollution.

Concrete batch plants that are located on MoDOT right of way will be covered under this General Permit with respect to MDNR and State Operating Permit requirements. However, all other appropriate permits will need to be obtained by the batch plant operators themselves. Operators of concrete batch plants that are located off of MoDOT right of way will be responsible for obtaining all appropriate permits directly from the DNR.

With respect to the State Operating Permit requirements, borrow sites located immediately contiguous with MoDOT right of way or owned by MoDOT are covered by this permit. For borrow activities located not on or not contiguous with MoDOT right of way, the borrow operator will be responsible for obtaining all appropriate permits, including a land disturbance permit directly from the DNR for borrow sites greater than one acre.

In the event of a conflict between these requirements and pollution control laws, rules, or regulations of other federal, state, or local agencies, the more restrictive laws, rules, or regulations shall apply.

806.8.4.2 Erosion Control Measures (MO Specifications - Special Provisions)

The following Best Management Practices (BMPs) shall be used by contractors to assure that eroded sediment from MoDOT right of way does not move off of MoDOT property and onto adjacent land or into streams and drainage channels.

These practices may be used as stand alone BMPs or may be used in combination with other practices to assure effective erosion control and off site delivery of pollutants. Other practices that are not listed here, or have not been identified or invented at the time of the preparation of this SWPPP, may be used if their performance is equivalent or better than the practices listed below.

806.8.4.2.1 Temporary Berms

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. These ridges are used temporarily at the top of newly constructed slopes to prevent excessive erosion until permanent controls are installed and/or slopes are stabilized. They are also used transverse to grade to divert runoff to stabilized slope drains.

Type A Berms are specified for use at the end of each day’s operations on embankments, will be constructed to specified dimensions (see MoDOT Standard Plan 806.10) and will be machine compacted with a minimum of one pass over the entire width of the berm with a dozer tread, grader wheel, etc. Type B Berms are specified when embankment operations are shut down over extended periods of time (i.e., winter), will be constructed to specified dimensions (see MoDOT Standard Plan 806.10) and will be machine compacted with a minimum of three passes over the entire width of the berm with a dozer tread, grader wheel, etc. Type C berms are specified at the toes of spill slopes around bridge construction operations and will be constructed to the specified dimension (see MoDOT Standard Plan 806.10).

Temporary berms must drain to a compacted outlet at a slope drain. The top width of these berms may be wider and the side slopes flatter on transverse berms to allow equipment to pass over these berms with minimal disruption.

806.8.4.2.2 Temporary Slope Drains

A temporary slope drain (see MoDOT Standard Plan 806.10) is used to carry water down slopes to reduce erosion and consists of stone, concrete or asphalt gutters, half-round pipe, metal pipe, plastic pipe, or flexible rubber pipe. Temporary slope drains are required on fill slopes at approximately 500 ft. intervals or as directed by the engineer.

All temporary slope drains will be adequately anchored to the slope to prevent disruption by the force of the water flowing in these drains. The inlet end will be properly constructed to channel water into the temporary drain. The outlet ends will have some means of dissipating the energy of the water to reduce erosion downstream. Unless otherwise specified, all temporary slope drains will be removed when no longer necessary and the site will be restored to match the surroundings.

806.8.4.2.3 Ditch Checks

There are two types of ditch checks that can be used – Type I and Type II.

Type I ditch checks are specified where drainage areas are 3 acres or less, ditch slopes are 10 percent or less and expected ditch flow volumes are small (see MoDOT Standard Plan 806.10). Type II ditch checks are specified where drainage areas are 50 acres or less, ditch slopes are 10 percent or less and expected ditch flow volumes are high (see MoDOT Standard Plan 806.10). For scenarios that exceed the criteria established above, a combination of Type II ditch checks and erosion control blankets are utilized.

Type I and II ditch checks shall be placed and constructed according to the plans shown in the Standard Plans For Highway Construction (Standard Plan 806.10). In some cases local conditions may dictate some deviation from the dimensions and shape that are shown in the Standard Plans; however, deviations from Standard Plans must still ensure that sediment capture is occurring. In order to be effective, all of these devices must be installed according to the manufacturers specifications.

Ditch checks shall be checked for sediment accumulation after each significant rainfall. Sediment shall be removed when it reaches one-half of the original height or before. Sediment removal will include removal and disposition in a location where it will not erode into construction areas or watercourses. Regular inspections shall be made to ensure that the center of the check is lower than the edges. This will ensure that water overflow will be directed into the middle of the roadway ditch. Erosion caused by high flows around the edges of the ditch check shall be identified in routine inspections and shall be corrected so as to protect backslopes and inslopes.

Type I ditch checks include the following devices:

Geotextile Silt Fence (staked)

Straw Bales (staked)

Fiber Rolls - < 8 “ (staked)

Dura Check Sediment Control Panel®

Type II ditch checks include the following devices:

Rock Ditch Checks

Sand Bags

Triangular Silt Dike®

EnviroBerm® Porous Sediment Control System

Fiber Rolls - > 8 “ (staked)

Compost Filter Socks

Filtrexx Ditch Chexx, Channel Soxx, Silt Soxx

GeoRidge (Nilex)

Compost Filter Berms

Landlok BioLog

Each type of ditch check (particularly the tubular/cylindrical/triangular products) will have specific directions for installation. In all cases care shall be exercised so as to install the device according to manufacturer specifications. Effectiveness may be compromised if not installed correctly.

806.8.4.2.4 Energy Dissipaters

An energy dissipater is a physical structure that is intended to reduce the erosive energy that is typically encountered down grade from a pipe or culvert. Erosive energy from intense flows may also be encountered in median ditches or road ditches. Energy dissipation may be accomplished by the installation of large boulders, wood pilings, engineered concrete structures or other means approved by the engineer. Unlike ditch checks and rock dams, energy dissipaters are not intended to impound water and sediment. Energy dissipaters must be constructed in a fashion such that the water that flows through, over or around the structure is equally distributed in the discharge channel and does not exacerbate or cause a resultant erosion problem.

806.8.4.2.5 Sediment Basin

A sediment basin is an excavated or dammed storage area with rock riprap placed in inlet and outlet areas with defined side slopes (see MoDOT Standard Plan 806.10). 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 occurs in spite of temporary erosion control measures.

Sediment basins shall be considered when large areas (greater than ten acres) concentrate flow to one discharge point, and where right of way is available. The area where a sediment basin is to be constructed shall be cleared of vegetation to enable removal of sediment. The inlets of these sediment basins shall be constructed with a wide cross section and minimum grade to prevent turbulence and allow deposition of the soil particles. When the depth of sediment reaches 1/3 of the depth of the structure in any part of the pool, all accumulation shall be removed. Discharges from the basin shall not cause scouring of the receiving area.

Sediment basins shall normally remain in service until all disturbed areas draining into the structure have been satisfactorily stabilized. When use of temporary sediment basins is to be discontinued, all excavations are to be backfilled and properly compacted, fill material removed, and the existing ground restored to its natural or intended condition.

When accumulated sediment and excavated material is removed from individual BMPs, the excavated material shall be disposed of in locations where sediment will not again erode into the construction areas or into natural waterways.

806.8.4.2.6 Sediment Traps

Sediment traps are small impoundments that allow sediment to settle out of construction runoff (see Sec 806.60. They are usually installed in a drainageway or other point of discharge from a disturbed area. Temporary diversions can be used to direct runoff to the sediment trap. Sediment traps detain sediments in stormwater runoff, and are formed by excavating an area or by placing an earthen embankment or rock dam across a low area or drainage swale. An outlet or spillway is often constructed using large stones or aggregate to slow the release of runoff.

Sediment traps are commonly used at the outlets of project sites and are generally installed at the time of clearing and grubbing. Do not use sediment traps for drainage areas greater than 5 acres. The effective life span of these structures is usually limited to 24 months. Although sediment traps allow eroded soils to settle, their detention periods are too short for removing fine particles like silts and clays.

For maximum effectiveness sediment traps should be long and narrow versus short and wide so as to achieve maximum retention time and avoid short-circuiting. However, right-of-way limitations will usually determine the optimum, resultant shape of the structure.

The primary maintenance consideration for temporary sediment traps is removing accumulated sediment. Sediment removal should occur when the basin reaches about 50 percent sediment capacity. Sediment traps should be evaluated after each rainfall event to ensure that the trap is draining properly and that damage from erosion has not occurred.

806.8.4.2.7 Inlet Controls

Storm drain (median or curb) inlet protection measures prevent soil and debris from entering storm drain inlets. Inlet protection is implemented at existing inlets prior to construction and new inlets are protected and as they are brought on-line. Effective storm drain inlet protection must be provided throughout the project until all sources with potential for discharging to an inlet have been paved or stabilized.

As the conditions or operations change during a project, the sediment control BMP protecting the storm drain inlet may need to be modified to ensure proper effectiveness for sediment capture. Limiting the amount of sediment entering a storm sewer will reduce the need to clean out pipes at the end of the project.

The following items are considered “prequalified” for use:

Rock Ditch Checks

Sand Bags

Triangular Silt Dike®

Fiber Rolls

Compost Filter Socks

Filtrexx Ditch Chexx, Channel Soxx, Silt Soxx

Compost Filter Berms

Landlok BioLog

Big Red Curb Inlet Protector

Silt Saver Inlet Filter

Dandy Products (Bag, Sack, Pop, Curb, Curb Bag, Curb Sack)

SOS (SOS erosionproducts.com) 2430, 3630, 4830

ERTEC Products (Curb Inlet , Combo, Drop, and GR-8 Guard)

Enviroscape Products (Vertipro)

Friendly Environment Products (Gutter Eel)

Blocksom Products (Inlet Filter)

During grading operations a temporary settling basin may be created by leaving the inlet opening slightly elevated above the bottom of the ditch so as to create a standpipe and temporary pooled condition. As with ditch checks, any accumulated sediment must be removed so as to provide sufficient volume for sediments to settle in the ditch. Safety considerations will dictate how high the inlet may extend above the bottom of the ditch.

806.8.4.2.8 Erosion Stabilization Mats and Blankets

Erosion control blankets, erosion stabilization mats, and turf reinforcement mats are designed to reinforce vegetation. The added reinforcement allows the vegetation to withstand higher flow velocities and can be an alternative to rip-rap applications.

Erosion stabilization mats are typically used to prevent sheet, rill or gully erosion. As such they may be used on slope areas with concentrated flow or in channels. Installation of erosion stabilization mats and blankets in channels will reduce the number and frequency of ditch checks depending on slope steepness, soil type, and other factors. In some cases blankets and mats may negate the need for ditch checks altogether.

Slopes should be stabilized immediately after grading work is completed. Soil retention blankets or turf reinforcement mats should be considered for most slopes steeper than 1V:3H; depending on soil types. Protecting slopes from erosion requires several actions that must be taken together. No single approach will be successful, especially if the slope is long, steep, or has highly erodible soils.

Prior to installation of blankets or mats the ground should be smooth, with no large rocks, vegetation or rills on the surface. Areas where blankets are to be used shall be properly prepared with topsoil or soil conditioning, and fertilized if required, and seeded before blankets are placed. The blankets shall be placed smoothly but loosely on the soil surface without stretching. Blankets at the top of the slope should be trenched in beyond the crest of the slope so as to avoid undercutting. In most cases, the manufacturers' installation recommendations must be followed, particularly regarding placement of anchors and the width of overlapping.

Prequalified Erosion Control Blanket
Type	Product Name	Manufacturer	Netting	Longevity	Slopes
Type 1	AEC Premier Straw Single Net - Quickly Degradable	American Excelsior	Single net, quickly degradable	45-60 days	1(V):3(H) or flatter
	Curlex 1 (0.73 LB/SqYd) - Quickly Degradable	American Excelsior
	Curlex 1 CL - Quickly Degradable	American Excelsior
	SR-1 Rapid Go Products	Western Excelsior
	R-1 Rapid Go Products	Western Excelsior
	DS-75	North American Green
Type 2	AEC Premier Straw Single Net	American Excelsior	Single photodegradable net	12 months	1(V):3(H) or flatter
	Curlex I (0.73 LB/SqYd)	American Excelsior
	Curlex I CL	American Excelsior
	SR-1 Excel Products	Western Excelsior
	R-1 Excel Products	Western Excelsior
	S75	North American Green
Type 3	AEC Premier Straw Double Net	American Excelsior	Double photodegradable net	12-18 months	1(V):2(H) or flatter
	Curlex II (0.73 lb/sq.yd)	American Excelsior
	SR-2 Excel Products	Western Excelsior
	R-2 Excel Products	Western Excelsior
	EG2s, EG1x, EG2x	Euro-Guard
	S-150	North American Green
	CFS072B	Greenfix America
Type 4	AEC Premier Straw/Coconut	American Excelsior	Double photodegradable net	24 months	1(V):2(H) or flatter
	Curlex III	American Excelsior
	EG2S/C, EG2C, EG2P___	Euro-Guard
	Landlok CS2	Propex Geosynthetics
	CS-3 Products	Western Excelsior
	SC150	North American Green
Type 5	AEC Premier Coconut	American Excelsior	Double photodegradable net	24 months	1(V):2(H) or flatter
	C125	North American Green
	EG2S/C, EG2C, EG2P___	Euro-Guard
	Curlex Enforcer	American Excelsior
	CC-4 Products	Western Excelsior
	Landlok C2	Propex Geosynthetics

Guidelines for Turf Reinforcement Mats

General: Use Erosion Control Blanket for Calculated Shear Stresses up to 3.5 lbs/ft² and use Turf Reinforcement Mat for Calculated Shear Stresses of 3.5 lbs/ft² or greater.

Type 1 Turf Reinforcement Mat

• Channels: Calculated Shear Stresses of 4 lbs/ft² to 6 lbs/ft²

Type 2 Turf Reinforcement Mat

• Channels: Calculated Shear Stresses of 6 lbs/ft² to 8 lbs/ft²

Type 3 Turf Reinforcement Mat

• Channels: Calculated Shear Stresses of 8 lbs/ft² to 10 lbs/ft²

Prequalified Turf Reinforcement Mat
Type	Product Name	Manufacturer
Type 1	Landlok 435	Propex Geosynthetics
	Recyclex TRM - V	American Excelsior
	PP5-8, PP5-10, PP5-12	WEstern Excelsior
Type 2	Landlok 450	Propex Geosynthetics
	P300	North American Green
	Recyclex TRM	American Excelsior
	PP5-10, PP5-12	Western Excelsior
Type 3	P550	North American Green
	PP5-10, PP5-12	Western Excelsior
	Pyramat Tan/Green	Propex Geosynthetics

The erosion control blankets and mats listed above are determined to be "prequalified". Additional products may be added by contacting MODOT Environmental Section, 573-526-6681, and submitting appropriate evaluation material from Erosion Control Technology Council.

In addition to the above list, products that have been approved by the Texas Transportation Institute (TTI) are also preapproved. A listing of these is available.

806.8.4.2.9 Seeding and Mulching (MO Specification Sec 802 & 805)

This work shall consist of preparing and fertilizing a seedbed, furnishing and sowing of seed, and mulching.

Seeding and/or mulching will be a continuous operation on all cut and fill slopes, waste sites, and borrow pits during the construction process. All disturbed areas shall be seeded and mulched when and where necessary to eliminate erosion. Seeding and/or mulching shall be done as soon as possible after completion of the earthwork. The State Operating Permit requires interim stabilization of slopes where land disturbance activities cease for 14 days. Seeding and/or mulching can satisfy this stabilization requirement, as can the installation and maintenance of sediment controls such as sediment basins, check dams and sediment fences.

Within a MODOT contract the primary purpose of “temporary” seeding is to provide a ground cover when a project is to be completed in stages, usually over the course of winter shutdown. While temporary seeding and mulching can produce a quick ground cover to reduce erosion in disturbed areas that are expected to be redisturbed at a later date, MODOT typically will not pay for "temporary" seeding that is performed simply for interim slope stabilization Sec 806.50.

Overspray is generally used to secure the vegetative mulch to slopes until seed germination and growth has occurred. However, embedment or other methods as approved by the engineer may be used in lieu of overspray. Blown straw products that include built in tackifiers and/or non toxic soil stabilizers (when applied according to manufacturers recommendations) do not require embedment or overspray.

Temporary mulch placed over temporary seed mixtures shall be applied in accordance with the provisions of Sec 802.2.1 of the Missouri Standard Specifications. Fertilizer shall be applied at the rate specified in Sec 806.50. Lime will usually not be required for temporary seeding but will be applied according to governing specifications when a permanent seed mixture is used.

Permanent seeding and mulching following the temporary seeding will be performed according to the Missouri Standard Specifications Sec 805.

806.8.4.2.10 Straw Bales (MO Specifications Sec 802)

Bales of straw can be used as a means of controlling pollution and erosion. The straw bales obstruct the flow of water allowing deposition of sediment and/or diversion of water. Other foliage may be substituted for straw in accordance with Sec 802.2.1 of the Missouri Standard Specifications.

This method is typically used at the bottom of embankment slopes to divert runoff from sheet flow and trap sediment, as a ditch check in small ditches and drainage areas, and on the lower side of the cleared areas to catch sediment from sheet flow. When used to trap sediment or divert runoff, the bales must be braced from behind. When used as a ditch check, embedment is required. Straw bales are most effective in areas where there is overland flow (runoff that flows over the surface of the ground as a thin, even layer). It is not effective in areas where there is a large volume of runoff.

The integrity of straw bales must be maintained for as long as they are necessary to contain sediment runoff. All straw bales shall be inspected immediately after each rainfall and at least daily during prolonged rainfall. Any deficiencies shall be immediately corrected. In addition, a daily review of the location of straw bales should be made in areas where construction activities have changed the natural contour and drainage runoff to ensure that the straw bales are properly located for effectiveness. Where deficiencies exist, additional straw bales shall be installed as approved or directed by the engineer.

Sediment deposits shall be removed and disposed of when the deposit approaches one-half the height of the bale or sooner. If required by heavy sediment loading, a second set of straw bales shall be installed as directed by the engineer.

The straw bales shall remain in place until the engineer directs that they be removed. Upon removal, the contractor shall remove and dispose of any excess silt accumulations, grade and dress the area to the satisfaction of the engineer, and establish vegetation on all bare areas.

806.8.4.2.11 Silt Fence (MO Specifications Sec 624 & Sec 1011)

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.

There are several construction requirements for silt fences. Fence construction shall be adequate to handle the stress from hydraulic and sediment loading. Geotextile at the bottom of the fence shall be buried. The trench shall be backfilled and the soil compacted over the geotextile. The geotextile shall be spliced together as indicated on the standard drawings (see MoDOT Standard Plan 806.10).

As a general rule silt fence should not be used around median inlets.

Post spacing shall not exceed 8 ft. for wire support fence installations or 5 ft. for self-supported installations. Posts shall be driven a minimum of 24 in. into the ground. Where rock is encountered, posts shall be installed in a manner approved by the engineer. Closer spacing, greater embedment depth and/or wider posts shall be used as necessary in low areas and soft or swampy ground to ensure adequate resistance to applied loads.

When support fence is used, the mesh shall be fastened securely to the up-slope side of the post. The mesh shall extend into the trench a minimum of 2 in. and extend a maximum of 36 in. above the original ground surface. When self-supported fence is used, the geotextile shall be securely fastened to fence posts.

When silt fence is used as a perimeter sediment control device it must be maintained for as long as necessary to contain sediment runoff. All silt fences shall be inspected as part of MODOT’s routine inspections after each rainfall and at least daily during prolonged rainfall. Any deficiencies shall be corrected within seven days following delivery of inspection report to contractor. In addition, a daily review of the location of silt fences should be made in areas where construction activities have changed the natural contour and drainage runoff to ensure that the silt fences are properly located for effectiveness. Where deficiencies exist, additional silt fences shall be installed as approved or directed by the engineer.

Sediment deposits shall be removed and disposed of when the deposit approaches one-half the height of the fence or sooner. If required by heavy sediment loading, a second silt fence shall be installed as directed by the engineer.

The silt fence shall remain in place until the engineer directs that it be removed. Upon removal, the contractor shall remove and dispose of any excess silt accumulations, grade and dress the area to the satisfaction of the engineer, and establish vegetation on all bare areas.

The engineer may substitute perimeter silt fence by any of the following commercial products:

Sediment STOP (North American Green)

Terra-Tubes (Profile Products)

Straw Wattles (Earth-Savers)

Compost Filter Socks

Triangular Silt Dike

806.8.4.2.12 Compost Filter Berms

A compost filter berm is a dike of compost or a compost product that is placed perpendicular to sheet flow runoff to control erosion in disturbed areas and retain sediment. It can be used in place of a traditional sediment and erosion control tool such as silt fence. Composts used in filter berms are made from a variety of feedstocks, including municipal yard trimmings, food residuals, separated municipal solid waste, biosolids and manure.

Compost filter berms are generally placed along the perimeter of a site, or at intervals along a slope, to capture sediment from sheet flow. A filter berm also may be used as a check dam in small drainage ditches. The berms may be vegetated or unvegetated. Vegetated filter berms are normally left in place and provide long-term filtration of storm water. Unvegetated berms are often broken down once construction is complete and the compost is spread around the site as a soil amendment or mulch.

806.8.4.2.13 Temporary Pipe

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. All temporary pipe shall be installed in the same manner as permanent pipe is installed on the project to assure that the water does not cause erosion around the pipe. Material to backfill the pipe should be placed in 6 in. lifts and mechanically compacted, although a compaction test is not required.

806.8.4.3 Additional Temporary Erosion and Sediment Control

806.8.4.3.1 Surface Roughening

Surface roughening is a temporary erosion control best management practice that is intended to aid in the establishment of vegetative cover with seed, to reduce runoff velocity and increase infiltration, and to reduce erosion and provide for sediment trapping. This practice is intended for areas which have been cleared and grubbed and are awaiting application of temporary or permanent seed, or installation of other structural controls such as ditch checks, rock dams or sediment basins. The practice is not intended to serve as a stand-alone best management practice and is only to be used as a short-term (2-3 weeks), sequential practice as the grading and seeding proceeds.

806.8.4.3.2 Mulching and Crimping

Application of mulch without seed may be used as a temporary best management practice if approved by the engineer. This practice is most applicable in late fall or early winter when grass seed would have little or no opportunity to germinate. Straw mulch should be applied with a mulch blower or by hand and must be anchored (crimped) immediately after spreading to prevent windblow. Application rates will vary based on the percent slope.

806.8.4.3.3 Brush Piles

Brush piles are considered to be a temporary BMP that is effective during clearing and grubbing operations. Tree tops, limbs, stumps and other vegetation, when placed in a drainage swale, can effectively impound gravel, soil and other eroded materials that otherwise may be carried off of MoDOT right of way during runoff periods. To be effective, brush piles should be compressed by clearing equipment at the time of installation. Like other BMPs, brush piles should be inspected following heavy rains to ensure that they are functioning as intended. If the brush pile is intended to serve as a semi-permanent structure for an extended period of time beyond the clearing and grubbing stage, clean out and maintenance equivalent to that required for Type I and Type II ditch checks is required.

806.8.5 Disturbed Areas

Project plans that are discussed in Site Description, will identify those areas that will be cleared and graded as part of the highway development project. Areas that are not to be disturbed are also shown on project plans. Such areas are also staked in the field.

Seeding and/or mulching will be a continuous operation on all cut and fill slopes, excess material sites, and borrow pits during the construction process. All disturbed areas shall be seeded and mulched when and where necessary to eliminate erosion. Seeding and/or mulching shall be done as soon as possible after completion of the earthwork and preparation of the seedbed, not to exceed 14 days, weather permitting.

806.8.6 Installation

The contractor shall be required to incorporate all permanent erosion control measures into the project at the earliest practicable time. Temporary erosion control measures shall be used to correct conditions that develop during construction which were not foreseen during the design stage. Temporary erosion control shall also be used when needed prior to installation of permanent erosion control measures or when needed temporarily to control erosion that develops during normal construction practices, but are not associated with permanent control measures on the project.

Clearing and grubbing operations shall be scheduled and performed so that grading operations and temporary and permanent erosion control measures will follow immediately thereafter. The surface area of erodible earth material exposed at one time by clearing and grubbing, by excavating, by fill, or by borrow, shall be minimized to prevent runoff. The engineer may limit the total acreage of erodible earth material to be exposed at one time as determined by an analysis of project conditions. In such cases the engineer will identify specific BMPs and controls that have been, or will be installed in order to exceed the specified maximum disturbed acreage threshold.

The engineer will limit the area of clearing and grubbing, excavation, borrow, and embankment operations in progress commensurate with the contractor's ability to keep the finish grading, mulching, seeding, and other erosion control measures current. Should seasonal limitations make such coordination unrealistic, temporary erosion control measures shall be implemented so as to protect the exposed soil from leaving the job site.

806.8.7 Dewatering

Dewatering of pits or excavations associated with pier construction shall be discussed at the preconstruction conference.

Standard Specification 107.10.2 requires a dike or barrier to be placed between the excavation and the stream to prevent sediment from reaching the watercourse. The structural BMPs that are identified in Erosion Control Measures are usually sufficient to remove sediment and drill cuttings prior to discharge of return water. Land application of the pumped water is a viable option when percolation into the subsurface results; however, caution shall be used to ensure that the pit water discharge does not cause the formation of gullies in cases where pumping exceeds percolation.

With the possible exception of drilled shafts in large rivers such as the Missouri or Mississippi, return water shall not be discharged without treatment by BMPs approved by the engineer. The amount of return water that is pumped and subsequently discharged shall be recorded in the inspector’s diary and expressed as gallons per minute for the duration of the pumping activity.

806.8.8 Amending/Updating the Project Plans

Erosion control plans are prepared by MoDOT designers and/or consultants and will show the final structural erosion controls that are envisioned upon completion of final grading. These plans usually will not be changed unless directed by the engineer. Interim erosion control measures at the start of the project shall be amended and updated as appropriate during the term of the land disturbance activity. The engineer shall require modifications to the erosion controls whenever the:

• Design of the construction project has changed in a fashion that could impact the quality of storm water discharges;
• MoDOT inspections indicate deficiencies in individual BMPs;
• MDNR notifies MoDOT of erosion control deficiencies on site;
• Erosion controls are determined to be ineffective in significantly minimizing or controlling erosion and sedimentation;
• MDNR determines violations of Water Quality Standards have occurred.

806.8.9 Site Inspection Reports

The resident engineer is responsible for evaluating the contractor’s erosion control devices and must ensure that weekly inspections are performed, as well as inspections following any rainfall event that could cause migration of eroded soil off of the site. Copies of the inspection reports are provided to the contractor, and deficiencies are to be corrected within seven calendar days.

MoDOT performs environmental compliance training to resident engineers, construction inspectors and other field staff to ensure that erosion control inspections are being conducted in a consistent fashion statewide. The individual who performs the training is organizationally located in MoDOT’s Environmental Section and does not have supervisory authority over the construction personnel who perform inspections. However, the same individual who performs training has the responsibility of performing statewide audits of construction sites to ensure that SWPPPs are being followed to the extent that off-site contamination does not occur. The individual usually will visit every construction site at least twice per year and meet with MoDOT resident engineers, inspectors or contractors to evaluate the land disturbance elements of the project and to ensure consistency of inspections. In cases where deficiencies are identified, the resident engineer has the responsibility to see that the deficiencies are corrected.

806.8.10 Diamond Grinding

Although diamond grinding is not a land disturbance activity, the fine material that is removed from the driving surface will become suspended in discharge water and has the potential to contaminate nearby streams if not sufficiently managed. The following shall be considered the minimum requirements for performing this work within the project limits in addition to Sec 622 and EPG 622.2.1 Construction Inspection for Diamond Grinding of Existing Portland Cement Concrete Pavement .

The contractor shall submit to the engineer for approval in writing prior to the pre-construction meeting, the best management practices (BMP’s) to be used to protect the environment, including the method of disposal whether on right of way or off-site.

The preferred BMP for slurry management is land application on MoDOT right of way. When slurry is dispersed on the right of way, BMPs shall be installed to keep slurry residue from entering drainage structures, from entering any waterways and from leaving the right of way.

Prior to starting work, slurry or residue “no discharge zones” will be identified by the engineer with respect to the contractor’s approved BMP and residue disposal plan.

The engineer may suspend operations during periods of rainfall or during freezing temperatures.

806.8.11 Turbidity Removal and Advanced Treatment Systems

Water clarification and the removal of turbidity will usually require the addition of flocculents, polymers, polyacrylamides (PAM), chitosan and other chemicals that cause soil particles to bind together, become heavy and settle to the bottom of a sediment trap or sediment basin.

Since settling of flocculated soil particles requires very slow moving (still) water, chemical additives should never be introduced into an outfall BMP where water leaves MODOT right of way. In all cases where chemical additives are used to reduce turbidity it is essential to include a sediment basin or sediment trap and a ditch liner or ditch check apron that prohibits additional erosion on the downgrade side of the ditch check.

The following Advanced Treatment Systems are pre-approved for use in MODOT projects where turbidity removal is required:

• Gel logs and Gel flats that are installed directly in a ditch, pipe or culvert upgrade from a sediment basin or sediment trap.

• Chitosan or PAM treated ditch checks (ie fiber rolls, wattles, or compost logs) that have been installed upgrade from a sediment basin or sediment trap.

• Chitosan or PAM treated rock ditch checks that have been installed upgrade from a sediment basin or sediment trap.

• Geo ridge ditch checks with attached chitosan or PAM bags, installed upgrade from a sediment basin or sediment trap.

• Addition of granular PAM or chitosan directly into a ditch, upgrade from a sediment basin or sediment trap.

• Terratubes

• Erosion control blankets and turf reinforcement mats that have been inoculated with PAM or chitosan, and installed upgrade from a sediment basin or sediment trap.

806.6.12 Chemical Stabilizers

Chemical stabilizers, also known as soil binders or soil palliatives, provide temporary soil stabilization. Various products are sprayed onto the surface of exposed soils to hold the soil in place and minimize erosion from runoff and wind. These materials are easily applied to the surface of the soil, can stabilize areas where vegetation cannot be established, and provide immediate protection.

Use chemical stabilizers alone in areas where other methods of stabilization are not effective because of environmental constraints, or use them in combination with vegetative or perimeter practices to enhance erosion and sediment control.

Closely follow the manufacturer's recommended application procedures to prevent the products from pooling and creating impervious areas where stormwater cannot infiltrate.

Inspect chemically stabilized areas regularly for signs of erosion, and if necessary, reapply the stabilizer.