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Erosion and Sediment Control
Pocketbook Guide
UNIVERSITY OF MINNESOTAErosion and Sediment Control Program
www.erosion.umn.eduJune 2009
Quick Reference
1’ = 1 ft = 1 foot1” = 1in = 1 inch
1:3 = 1 vertical to 3 horizontal slope
BMP = Best Management Practice, or any product or activity that effectively assists with stormwater management
BWSR = Minnesota Board of Water and Soil Resources
EPA = Federal Environmental Protection Agency
MPCA = Minnesota Pollution Control Agency
NPDES/SDS = National Pollutant Discharge Elimination System/State Disposal System
NTU = Nephelometric Turbidity Unit, an index measure of water quality
SWPPP = Stormwater Pollution Prevention Plan
TMDL = Total Maximum Daily Load, a measure of pollution, also used to describe impaired waters
Minnesota Pollution Control Agency Duty Officer
800-422-0798
Department of Natural Resourceshttp://files.dnr.state.mn.us/waters/area_hydros.
Sediment Control ....................................................2 Buffers ......................................................2 Silt Fence ......................................................2 Bale Barriers ....................................................5 Sandbags ......................................................6 Storm Drain Inlet Protection.............................7 Culvert Protection.............................................9 Sediment Traps...............................................10 Silt Curtain ....................................................12 Sediment Mat .................................................15 Filter Logs ....................................................15 Flocculants ....................................................18Erosion Control .....................................................20 Smooth-Rough Grading .................................20 Cat Tracking....................................................20 Temporary Ditch Checks ................................21 Riprap ............................................................25 Mulch..............................................................27 Erosion Control Blankets ...............................31 Hydraulic Soil Stabilizers ...............................36 Temporary Down Drains ................................40 Compost ........................................................42 Erosion Stabilization Mats .............................43Seeding ..................................................................45 Soil Preparation .............................................45 Fertilizer and Lime..........................................46 Seed and Seeding .........................................48
Sod .........................................................................52 Soil Preparation .............................................52 Fertilizer and Lime..........................................53 Material and Placement .................................53General Operations ..............................................57 Dewatering ....................................................57 Concrete Washout.........................................61 Structure Removal.........................................62 Dust and Airborne Particles ..........................62 Chemicals Fueling Haz Waste Handling.......63 Stockpile Protection.......................................63 Street Sweeping ...........................................64 Sediment Removal .......................................66 Sensitive Area Protection..............................66
Table of Contents
Erosion and Sediment Control Certification Program
Department of Bioproducts and Biosystems Engineering
University of Minnesota1390 Eckles Avenue
St. Paul, MN 55108-6005
www.erosion.umn.edu
ost construction projects require the placement of adequate erosion and sediment control devices to meet pollution control regulations. Being proactive, aware
of site conditions, and properly installing erosion and sediment control devices will save time and money by reducing the amount of sediment removal, re-grading, the potential for costly fines, and the need to reinstall devices.
This pocketbook is intended for inspectors and installers of erosion and sediment control devices. The installation methods primarily correspond to Mn/DOT’s 2005 Standard Specifications for Construction, Standard Plan sheets, and other industry standards. The 2000 section of the specifications contains information regarding installation, maintenance and payment. The 3000 section of the specifications contains information related to the required materials.
Always check your specific project for special provisions for new devices or changes. All Mn/DOT approved products are listed on the internet at: www.mrr.dot.state.mn.us
For questions related to Mn/DOT plans or projects concerning erosion, sediment and NPDES topics call the Erosion Control Engineering Unit in Environmental Services at 651-366-3629.
For general questions concerning erosion, sediment and NPDES topics call the University of Minnesota at 612-626-4857, email [email protected], or visit www.erosion.umn.edu.
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Sediment ControlSediment control devices must be installed to protect water resources, storm sewer systems and adjacent properties BEFORE land disturbing activities begin. Sediment control devices may have to be staged to provide appropriate protection as the project progresses or site conditions change.
Buffers
Grass buffers, or maintaining existing vegetation at the site perimeter can provide effective sediment control. Buffers can be useful in construction stages such as clearing and grubbing operations that may interfere with other sediment control techniques.
Silt Fence (Mn/DOT Specifications 3886 and 2573)
Silt Fence is generally used as perimeter control to keep sediment on-site. It can also be used to keep sediment-laden runoff from entering an area you want to protect, such as a newly created wetland surrounded by on-going construction. Common types used are Machine-sliced and Heavy duty, although pre-assembled types are also available. Super duty (median barriers lined with silt fence fabric) is used for steep slope protection as well as protecting areas next to stockpiles.
MaterialMachine Sliced and Heavy Duty Each roll of geotextile should have the
manufacturer’s name and product number. This should be cross-checked with the approved materials list.
Geotextile is made by weaving two monofilament strands in opposite directions.
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Geotextile is 3’ wide.
Posts are standard steel T-posts with a welded plate a minimum of 5’ long.
Super Duty Geotextile consistent with Machine Sliced and
Heavy Duty.
Precast Concrete Median Barrier conforming to 2533.
Installation of Machine Sliced
Figure 1
Use proper equipment such that the soil is sliced, not turned over.
Geotextile fabric embedded 8” to 12” in a soil slit, leaving about 2’ of fabric above ground.
Compact the soil immediately next to the geo-textile by driving over it with a tractor tire at least twice.
Monofilament GeotextileYou can see through the fence at a distance.
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Steel T-posts placed on downstream side of water flow embedded at least 2’ into the ground. Maximum spacing 6’. Nipples on post face away from the geotextile to keep ties from slipping on post.
Use 3 plastic zip ties at least 1” apart to secure the geotextile to each post within the top 8”.
Installation of Heavy Duty
Figure 2
Geotextile fabric embedded in a 6” deep by 4” wide trench with the bottom edge of the geotextile wrapping back up to the soil surface. The trench is backfilled and tamped for compaction.
Posts and ties are the same as machine sliced silt fence.
Installation of Super Duty Place bottom edge of geotextile 4" to 6"
underneath the face of the median barrier that receives runoff.
Place barriers end-to-end to minimize the gap.
Attach geotextile to face of barrier at each barrier’s eyelets using wire or plastic zip ties within the top 8” of the fabric.
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Winter Installation Trenching into frozen ground is not often practical. Alternatives include placing filter rock continuously along a 10” fabric lip to hold the fence until the ground thaws. This technique can also be used over tree roots or shallow utilities.
RemovalAll silt fence must be removed before the NPDES permit can be terminated.
Bale Barriers (Mn/DOT Specifications 3882 (Type 1) and 2573)
Hay bales can be used in wet marshy areas or shallow standing water where silt fence cannot be installed. The bales act as a sediment capture berm. Mn/DOT does not recommend hay bales for use as ditch checks as they ultimately create more erosion problems. If bales are to be used, they can be reinforced by installing a blanket in the ditch bottom, carrying the blanket up and over the bales making direct contact between the bales and blanket, and finally stapling the blanket in the ditch bottom on the back side of the bales. The blanket reduces erosion on the back side of the bales.
Alternatives to bale ditch checks include biorolls, rock
Figure 3
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checks, compost logs, rock logs and silt fence.
Material Bales are to conform to 3882 Type 1 mulch
requirements.
Densely packed rectangular shaped 14” x 18” x 36” minimum.
Installation In wet soft areas, the bales can be pushed into
the ground abutting one another forming a bale barrier line.
OR Trench into the ground 4”.
Two 2” x 2” wood stakes through each bale, driven into the ground a minimum of 10”.
Removal Bales used at the edge of wetlands can be
left in place and will rot away. Remove only if requested by the Project Engineer or Agency personnel.
Bales used as a ditch check must be removed at the completion of rough grading. Bales are not to remain in place during final shaping and seed-ing.
Sandbags (Mn/DOT Specifications 3893 & 2573)
Sandbags can be used to temporarily dike off areas, divert water, control a ditch grade, seal off riser standpipes, and to assist with inlet protection. Sandbags should be removed before the bag fabric deteriorates.
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Storm Drain Inlet Protection(Mn/DOT Specifications 3891 & 2573)
Storm drain inlets must be protected with sediment capture devices prior to soil disturbing activities that would result in sediment laden storm water runoff entering the inlet. 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 best management practice protecting the storm drain inlet may need to be modified to ensure proper effectiveness for sediment capture. Limiting the amount of sediment entering into a storm sewer will reduce the need to clean out pipes at the end of the project.
Caution: Inlet protection devices need to be inspected and cleaned out regularly especially if the road is open to traffic. ALL inlet devices should have an emergency overflow or bypass feature equivalent in size to the apparent grate opening size. Captured sediment may reduce the flow rate of the inlet protection device and can result in flooding or icing conditions. For safety reasons, inspect for proper drainage during a runoff event to ensure the road is safely open to traffic.
Inlet protection is a rapidly changing industry as new requirements and needs are constantly arising. Always check the plan and special provisions first for information.
MaterialDevices can be created in the field, examples are shown on standard plan sheets, or a prefabricated product can be used. Devices need to change as the inlet changes; no curb head to having a curb head, for example. One size does not fit all. Some devices sit on top of the inlet or surround the inlet
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Bioroll and Bag Silt Fence Box
Drop-in prefabricatedPopup
while others are housed inside the catch basin. Other material may be necessary such as small rock to act as a pre-filter to the inlet protection device.
See the APPROVED PRODUCTS LIST for pre-approved fabricated products.
In addition to the Approved Products List, other approved materials or combinations of materials can be furnished for use. When choosing a product to protect an inlet you should take into account the contributing drainage area, soil type, the corresponding environmental sensitivity of the receiving end, type and location of inlet, and safety considerations such as the effect of the potential localized flooding conditions. Additional approved materials that can be considered for use are: rock logs, compost logs, sediment control inlet hat, silt fence ring and rock filter berm or rock log combination, pop-up head, and filter bag inserts.
InstallationInlet protection devices need to be installed just prior to disturbing soil areas that would drain directly into the inlet. Installation should be such that the device fits the inlet properly without gaps, such as in the curb back. Devices that sit on top of the inlet need to be secured to the ground to keep the device from floating away.
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Freezing conditions may require the temporary removal of devices. This should be recorded, along with the site conditions and safety concerns in the project documentation.
RemovalRemove the inlet protection device immediately once all sources with potential for discharging to the inlet have been stabilized. Areas surrounding the protected inlets should be stabilized with erosion control practices as quickly as possible. Culvert Protection (Mn/DOT Specification 2573 and Plan Sheets)
Culverts that outlet water off the project’s right-of-way or into surface waters need to have sediment control devices installed. Sediment control is most effective when placed on the inlet side, so sediment is not trapped in the culvert. Culverts in sediment basins have more sediment control options due to the ability to pond water without causing additional flooding problems. Examples of culvert protection include:
Geotextile wrapped over the inlet Silt fence on the slope above the inlet Placing a rock weeper before the inlet Placing a perforated riser pipe in the inlet Placing a temporary weir board against the inlet
Culvert inlet covered by pipe’s geotextile wrap
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Sediment Traps (Mn/DOT Specification 2573 & Standard Plan Sheet)
Sediment traps help reduce flow velocities in ditches and capture sediment. Typical locations include ditch bottoms, the downgrade end of a cut section, and areas where it becomes necessary to capture larger amounts of sediment such as where a silt fence continually fails. In the later case, the silt fence should be reinstalled approximately 10’ from the sediment trap outlet.
InstallationSediment traps are usually temporary. For this reason, traps are usually located in problem areas that have developed during construction. Guidance for construction is shown in Figure 4. In general, traps are two times longer than wide and 2 ft deep. Rock can be used to limit erosion and provide some additional filtration.
Sediment Trap at the end of a cut-runout section.
Linear sediment trap
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Linear sediment traps can also be used to provide extra sediment storage along a perimeter or at the bottom of a long, steep slope. Linear sediment traps should not be dug very wide (2‘ max) or deep (1’ max). If too much soil is removed at the bottom of a slope, the slope may become unstable and major soil failures could result.
RemovalTemporary sediment traps can be filled in and graded over at the time of final shaping. The rock from the outlet could be buried or removed.
Location where sediment trap with rock outlet would be beneficial
Figure 4
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Silt Curtain (Mn/DOT Specifications 3887 & 2573)
Silt curtain can be used in moving water or still water conditions to isolate sediment from a water body. Sediment captured behind the silt curtain should be removed before the curtain is pulled out.
MaterialFlotation silt curtain is constructed of impermeable vinyl-coated nylon fastened to a flotation carrier and weighted along the bottom edge. Note: There are separate requirements for still and moving water applications.
InstallationStill water: The curtain needs to be anchored along its length with enough weight to hold it in place. Both ends need to be secured on land.
Figure 5Floating Silt Curtain - Still Water Application
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Figure 6
Figure 7
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Figure 8Floating Silt Curtain Cross Section
Moving water: A buoy accompanies each anchor in the waterway. The curtain should be angled upstream and anchored with a minimum of 300 lbs out in the waterway, placed a minimum of 25’ from temporary fill, and secured to land.
Work Area: When the work area extends less than 1/4 of the stream width, the area is enclosed with a silt curtain. The curtain should extend outward from shore at a 45-degree angle and should not extend more than 1/3 of the stream width. Anchor with a minimum of 40 lbs at a maximum of 100’ intervals.
Figure 8 applies to the moving water scenario. Still water and work area types differ in that they do not need the anchor cable and anchor as shown and the curtain rests on the bottom unless the water depth is greater than 4’.
GeneralDo NOT place silt curtain across a flowing channel in its entirety. The channel bottom may experience scouring. If silt curtain is necessary in flowing water to capture up-stream disturbance, place the curtains diagonally, alternating from each stream bank and maintaining frequently. Do NOT extend the silt curtain out more than 1/3 of the stream width. Maintenance and RemovalRemoval shall be done in a manner to prevent re-
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suspension of sediment. Sediment behind the curtain should be cleaned out frequently and before curtain removal. Silt fence or a similar sediment control device should be installed at the toe of the slope before the silt curtain is removed and remain in place until the vegetation is established.
Sediment Mat
Sediment mats are fiber mats placed in slow (less than 5 fps) shallow water (less than 2’) to capture sediment. The sediment trapped in the mat is retained when the mat is removed from the water and disposed. While in-stream sediment capture is not adequate for some agencies, this product could be used to aid in maintenance and sediment removal behind floating silt curtain.
Filter Logs (Mn/DOT Specifications 3897 & 2573)
Filter logs, also called wattles or SRFRs (sediment retention fiber rolls) by the erosion control industry, are filtering material in a fabric or netting tube used for slowing water, and filtering storm water runoff or other water encountered on the project. Because of their flexibility filter logs can be used in numerous ways and in a multitude of locations, i.e. ditch checks, inlet protection and directing or diverting water runoff.
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MaterialStraw and Wood Fiber Bioroll Both straw and wood fiber biorolls are encased
in a polypropylene netting that photo degrades within 6 to 9 months.
The netting has approximately 0.5” x 0.5” openings.
The rolls are a minimum of 10’ long and 6” to 7” in diameter.
Straw biorolls are made from grain straw that is free from seed bearing stalks of noxious grasses or weeds.
Wood biorolls are made from excelsior fibers that are approximately 6” long.
Compost Log The compost used is a blend of 30% – 40%
Grade 2 (Spec 3890) and 60% - 70% partially decomposed wood chips.
The compost blend is pneumatically shot into a geotextile tube.
Compost logs can be made in various diameters.
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The geotextile bag is a knitted material with openings of 3/8”.
Maximum length of the log is 180’ and 8” in di-ameter.
Rock Log The bag is filled with washed rock meeting Spec.
3137 Class D with a gradation in accordance with Table 3137-1: CA-1 to CA-5.
The bag is between 4’ – 10’ long and 4” – 6” in diameter when full
Installation of Straw or Wood Biorolls and Compost Logs Staked into the ground with wood stakes.
Wood stakes are a minimum 0.5” x 2” nominal by 16” long and placed every 1’ unless precluded by paved surface or rock.
Wood stakes are driven through back half of bioroll or compost log at an approximate 45º angle with top of stake pointing upstream.
When more than 1 bioroll/compost log is need-ed, overlap ends a minimum of 6" and stake.
Note direction of stakes
Flow
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Installation of Rock Log Rock logs are typically used on paved surfaces,
bedrock, or frozen ground; therefore staking is not possible. The weight of the log is usually sufficient to keep it in place.
RemovalFilter logs must be removed before terminating the project unless the Project Engineer requests otherwise.
Flocculants (Mn/DOT Specifications 3898 & 2573)
Flocculants are added to water to aid settlement of clay particles to reduce the project’s water turbidity before discharging to a natural surface water. It is important to use the proper amount of flocculant for your situation. The treated water should flow through a grass waterway, rock checks or weepers, sediment traps, or basins before being discharged to a natural surface water.
MaterialAll flocculants need to be environmentally benign, biodegradable and consist of natural origin biopolymers.
Liquid Flocculant Stored in a concentrated liquid state with the
container listing the percent of concentration and the application dose rate.
Flocculant Sock Contained in a gelatin-like state and packaged
in individual compartments of the encasing sock material. The encasing sock material allows water to enter and make contact with the flocculant.
The ends of the encasing sock have anchor
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cords or grommets to attach or anchor the sock.
The flocculant contained in the sock can treat 250,000 gallons of dirty water.
Granular Flocculant Stored in a granular state with the bag or con-
tainer listing the purity and application mixing rate.
Installation/ApplicationAll flocculants must be used in a designed treatment system. Flocculant should not be directly applied to natural surface waters unless you receive written permission by the regulating party, due to the oxygen demand of the reaction.
Flocculant effectiveness can depend on water pH, water temperature, soil type, and other factors so bench tests are recommended prior to application. Liquid and Granular Flocculant All dose rate calculations must be verified by the
Engineer prior to use.
Flocculant Sock The sock is to be attached or anchored such that
during treatment the sock is in direct contact with the water.
The sock is to be monitored to ensure that the flocculant has not completely dissolved.
A sock at the end of a culvert into a sediment basin. The sock material causes soil particles in the water to bind together and drop out of suspension.
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Erosion ControlErosion control devices reduce the erosion potential of the soil and are key to limiting the amount of sediment produced. Erosion control can be installed as a temporary measure or as a permanent application. Temporary cover must be placed in the timeframes required by permits or as stated in the plan. The most common temporary cover is temporary seed with disk-anchored mulch. The amount of temporary erosion control can be greatly reduced if small areas are promptly shaped up to final grade followed by immediate permanent seeding and mulching.
Smooth-Rough Grading (Mn/DOT Specification 2575)
Smooth-rough grading is to be used when the final topsoil grade has not been established and temporary erosion control products or temporary seeding must be installed. It removes large clods of soil greater than 3” diameter and ruts deeper than 3”. There is no direct payment for this item as it is part of installing adequate and effective temporary erosion control items.
Cat Tracking (Mn/DOT Specification 2575)
Cat tracking, also known as horizontal slope grading,
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significantly reduces the erosion potential. Cat tracking is achieved by driving the dozer vertically up and down the slope. This results in the tracks being oriented horizontally, creating small speed bumps for water. These tracks also help mulch and seed stay in place better when it rains. When a dozer drives horizontally on the slope, the tracks are left vertically, leaving behind pre-formed erosion rills.
On all slopes 1:3 and greater with a length of 50’ or more, cat tracking should be done at the end of each day the slope is worked. Cat tracking works especially well on sands and silt soils.
No payment is typically made for this practice. This practice can save time for the contractor in the long run by reducing maintenance time for sediment re-moval and less re-grading of slopes after rainfall.
Temporary Ditch Checks (Mn/DOT Specifications 3889 & 2573)
Properly spaced ditch checks slow the water velocity in a ditch, which helps to reduce the amount of erosion the ditch will experience. Ditch checks can also trap incremental amounts of sediment, reducing the overall stress on the final sediment capture device.
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The effectiveness of a ditch check is related to the ditch gradient, expected flow velocity and soil type. Ditch checks are arranged in increasing order to manage the increasing degree of protection a ditch may need. Silt fence is only appropriate for low flow ditches less at than 3% grade.
Type 1: Sliced in Silt FenceType 2: BiorollType 3: Bioroll Blanket SystemType 5: Rock WeeperType 6: Geotextile Triangular DikeType 7: Rock Check
MaterialType 1: Sliced in Silt Fence The geotextile must meet the same
specifications as outlined in the Silt Fence Section under Machine Sliced.
Type 2: Bioroll The bioroll must meet the same specifications as
outlined in the Filter Log section under bioroll.
Type 3: Bioroll Blanket System The blanket must meet the same specifications
as outlined in Erosion Control Blanket under Category 3.
The bioroll must meet the same specifications as outlined in the Filter Log section under bioroll.
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Type 5: Rock Weeper The coarse concrete aggregate forming the front
half of the weeper must meet specification Table 3137-1: CA-1 gradation.
The riprap forming the back half of the weeper must meet specification 3601, Class I and be composed of 100% crushed or quarry run material.
The geotextile filter fabric liner must meet specification 3733 Type IV.
Type 7: Rock Check Rock is to meet the Specifications of 3601 Class
I–IV, as specified.
Geotextile filter fabric to meet Type IV of Specification 3733.
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InstallationAll ditch checks must be placed so that the bottom of the outer edges are higher (minimum of 6” preferred) than the top of the center of the ditch check. This will force water over the center of the check, rather than around the edges. In winter, rock materials are typically perferred due to difficulties with stakes and stapes in frozen ground.
Type 1: Sliced in Silt Fence The installation is the same as machine sliced
silt fence with the exception that the posts are spaced to a maximum of 4’.
Type 2: Bioroll The bioroll is anchored with wood 0.5" x 2"
stakes at a maximum spacing of 1’. The stakes should be angled such that the force of the water would cause the stake to rotate up vertically.
If more than 1 bioroll is needed to properly span the distance of the ditch, the ends should be overlapped about 6"
Type 3: Bioroll Blanket System The erosion control blanket is rolled out across
the ditch and trenched in 4” on the upgrade side.
6” - 8” U-staples are placed every 1’ on center, according to Mn/DOT specifications. The
manufacturer’s recommendations are to staple every 20” across the blanket and place a row every 2’ lengthwise.
The bioroll is anchored on the center of the blanket with wood 0.5” x 2” stakes at a maximum spacing of 1’. The stakes should be angled such that the force of the water would cause the stake to rotate up vertically.
If more than 1 bioroll is needed to properly span the distance of the ditch, the ends should be
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overlapped about 6”.
Type 5: Rock Weeper The Type IV geotextile is placed to line the
bottom of the rock weeper.
The overall weeper side profile forms a triangle.
The coarse concrete aggregate (filter rock) forms the front half of the weeper at a 1:2 (V:H) slope up to a vertical height of 2’ unless specified otherwise.
The riprap forms the back half of the weeper with a 1:2 backslope.
Type 7: Rock Check The Type IV geotextile filter fabric is placed to
line the bottom of the rock check.
The overall side profile forms a trapezoidal shaped berm with the bottom being approximately 5’ wide and the top being 2’ wide. The approximate depth of the berm is 1.5’ to 2’.
RemovalAll ditch checks must be removed before permanent shaping and seeding.
Riprap (Specifications 3601 & 2511)
Riprap is typically used to dissipate water energy such as at the end of a culvert. It is also used where vegetation would not be able to withstand the predicted water flow velocities such as under high channel flows.
MaterialsThe riprap should be designated in the plan with the appropriate class for the situation. See specification 3601 for the detailed gradation requirements of each
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class. In general, the average rock diameter and mass is listed below.
Rip rap Class Mass of Median Size of Median
I 2 lbs 3 inches II 15 lbs 6 inches III 50 lbs 9 inches IV 120 lbs 12 inches V 250 lbs 15 inches
The appropriate type of granular filter or geotextile fil-ter fabric should be determined by specification 3601 or 3733.
InstallationRip rap thickness is typically 1.5 times the largest stone size. For plunge pools at the end of culverts, the pool area needs to be excavated such that when the rock is placed, water flows out of the apron onto the top of the rock and then down into a pool. If the rock is placed too high, the rock will either be pushed away from the apron due to the force of the water or major erosion will result from water running under the rock. When riprap is placed as a ditch liner it is important for the riprap to be keyed in, or matched with the ground line. This will create a nice transition from soil to rock. If the rock is placed too high or too low compared to the surrounding soil, water will erode the soil along side of the rock/soil transition and slumping of the slope will occur.
Riprap was placed too high at the end of the culvert. Water cut a channel to the side of the outlet where it found the least resistance.
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Mulch (Specifications 3882 & 2575)
Mulch can be placed as temporary or permanent. Temporary mulch follows the same requirements as permanent mulch, just applied at different times during construction. Temporary mulch is placed on slopes that are not ready for permanent seeding and construction has temporarily stopped on the slope. This may happen due to weather conditions, necessary consolidation time, or focusing on another portion of the project. Temporary mulch can also be placed when you are outside of the seeding dates to protect slopes that are ready for permanent seeding. The NPDES permit also requires soils to have some type of cover if they are unworked within a certain amount of time. Temporary mulch can be incorporated into the soil when construction begins again on the slope. Permanent mulch is applied after the permanent seeding and will not be re-disturbed.
MaterialType 1: Grain straw, hay, or cuttings of agricultural grasses and legumes. Mulch must be in an air dried condition at delivery.
Free from noxious weed seed.
Does not contain Canada thistle, leafy spurge, cattail, reed canary grass, birds-foot trefoil or
Riprap nicely transitioned
between soil and rock.
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crown vetch.
If Type 1 mulch is used with native seeding, it must be grain straw.
Type 3: Clean grain straw Certified by the Minnesota Crop Improvement
Association (MCIA) to be weed free.
At delivery, all bales need to have a MCIA uniquely numbered tag attached to the bale and be in an air-dried condition.
Type 4: Type 1 mulch over-sprayed with Type 5 Hy-draulic soil stabilizer
Type 5: Project-produced Wood Chips Raw wood material from hard or soft timber
harvested during clearing and grubbing operations on the project.
Wood is chipped or ground such that it would pass a 4" screen with not more than 20% by mass passing a 0.1" sieve.
Type 6: Wood chips Mostly free from mold, dirt, sawdust and not
decomposed.
Does not contain manufactured boards or
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chemically treated wood.
Wood is chipped or ground such that it would pass a 4" screen with not more than 20% by mass passing a 0.1" sieve.
Type 9: Aggregate 3/8" to 2" in diameter
InstallationType 1 & 3: If disk anchoring will be used, the soil should first
be loosened before applying the mulch.
Mulch-blowing equipment should not be operated on slopes that are too steep for the equipment or that cause rutting of the soil surface (slopes 1:3 and steeper). Blower attachments should be used so that the mulch can be applied without having to traverse steep slopes.
Apply at approximately 2 tons/acre such that 90% of the ground is covered.
An even coverage must be obtained. Areas with clumps or streaks must have some mulch re-moved/reworked and areas that are too thin must have mulch reapplied.
�0% uniform mulch coverage with disk anchoring.
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Type 4: Apply Type 1 mulch at 1.5 tons/acre and im-
mediately over-spray with Type 5 Hydraulic Soil Stabilizer at 750 lbs/acre.
Type 5: When using as an erosion control blanket-type
material, apply at 80 yd3/acre. Also used for work pads and perimeter berms
Type 6 & 9: See plan or special provision for application rate
and procedure.
Winter: On frozen ground, applying water at 2000
gallons per acre over mulch can be substituted for disk anchoring
On snow, consult plans for application rate reductions from 2 tons to 1.5 tons per acre.
RemovalTemporary mulch can be incorporated into the soil as the construction progresses before permanent
Mulch is too thick, in this case ap-proximately �”. The mulch smothered the seed.
Disk anchoring was not effective because the soil was not loosened
before mulching as shown by the existence
of the cat tracks. Most mulch blew away.
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seeding and mulching take place. If temporary mulch has been placed on topsoil at final grade the permanent seed can be interseeded into the mulch. Additional mulch may have to be applied to achieve a uniform 90% final coverage.
Erosion Control Blankets (Specifications 3885 & 2575)
Erosion control blankets, also called temporary RECPs (temporary rolled erosion control products), can be used to stabilize soils temporarily until vegetation is established. Common uses are the last 200’ of a ditch bottom that drains to a surface water or exits property; bridge end slopes that need time to consolidate; corners of ponds receiving concentrated flow; and 1 blanket width ringing the normal water level of a pond.
Blankets are used wherever mulch would be ineffective or is too difficult to place. These areas include slopes steeper than 1v:3h, areas where the mulch would blow away such as the inslope, concentrated flow areas such as ditch bottoms (up to 5% grade), and narrow areas where a tractor could not maneuver.
A blanket that has rapid degradable netting and stitching should be used in areas where mowing will take place. It has been found that using a blanket without rapid degradable stitching can cause harm to a mower’s bearings.
There are 9 categories of blanket in the Mn/DOT specification. The Erosion Control Technology Council classifies temporary RECPs into 4 types based on longevity, with subtypes for materials. Each category corresponds to a different site condition.
MaterialsSee the APPROVED PRODUCTS LIST for pre-ap-proved blankets in each category.
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Category 00: The netting is only on the top of the blanket
and it is rapid degradable. The netting should begin to lose its integrity and strength within 6 to 8 weeks of sunlight exposure. There are no threads or stitching holding the fibers to the net-ting. The fibers are wood cellulose at least ½” long.
Category 0: There are no nets in this blanket, only stitching
that is rapid degradable. The stitching should begin to lose its integrity and strength within 6 to 8 weeks of sunlight exposure. The blanket fibers are wood at least 6" long. The primary bonding agent holding the wood fibers together is glue.
Category 1: The netting is only on the top of the blanket and
it is rapid degradable. The stitching should be rapid degradable as well. The netting and stitch-ing should begin to lose its integrity and strength within 4 to 12 weeks of sunlight exposure. The fibers can be either straw or wood.
Category 2: The netting is only on the top of the blanket and
will last approximately 1 growing season before losing its integrity. The fibers can be either straw or wood. It is not to be used in concentrated flow areas.
Category 3: The netting is on both the top and bottom of the
blanket and will last approximately 1 growing season before losing its integrity. The fibers can be either straw or wood. Used primarily on mod-erate slopes and in ditch bottoms less than 3%.
Category 4: The netting is on both the top and bottom of the
blanket and will last approximately 2 to 3 years before losing its integrity. The fibers can be either a blend of 70% straw and 30% coconut, or a
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high velocity wood fiber. Primarily used on steep slopes and higher flowing ditch bottoms up to a 4% grade.
Category 5: The netting is on both the top and bottom of the
blanket and will last approximately 2 to 3 years before losing its integrity. The fibers are a blend of 30% straw and 70% coconut. Primarily used in stream bank restoration projects or in ditch bot-toms up to a 5% grade.
Category 6: There are more than 2 nets forming a 3-
dimensional matrix with the fibers. The nets will last at least 3 years before losing its integrity. The fibers can be either a 70% straw and 30% coconut blend, or a wood fiber.
Category 7: There are more than 2 nets forming a 3-
dimensional matrix with the fibers. The nets will last at least 3 years before losing its integrity. The fibers can be either pure coconut or wood.
Staples/Anchors:The type of anchors used to secure the blanket to the ground depend on the category of blanket installed.
Blanket MinimumCategory Material Type Width Length00 & 0 Biodegradable Hook 0.375” 5” shaped diameter stake1 & 2 Steel wire 11 Gauge 1” 4”3 & 4 Steel wire 11 Gauge 1” 6”5, 6, & 7 Steel wire 11 Gauge 1” 8”
InstallationBefore laying the blanket, the soil should be shaped and prepared such that it is free of large rocks, soil clumps or vehicle imprints that would prevent the blanket from lying flush to the soil.
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Adequate stapling is the biggest factor in determining if a blanket will be successful or if it will fail. The stapling pattern is dependent on the degree of the slope, or if it is placed in a ditch bottom or channel. The stapling pattern changes slightly when an 8’ blanket is used as compared to a 6.5’ blanket, but the number of staples per square yard remains the same.
The leading blanket must have the upgrade end buried and stapled into a check slot. The check slot helps to keep water on top of the blanket rather than undermining the blanket immediately. The exception is when a blanket strip is used along the edge of the shoulder; the entire edge length adjacent to the shoulder must be buried into a check slot. This method ensures the blanket will remain in place during repeated exposure to wind created by traffic, and from runoff exposure.
A check slot is a trench dug 6” deep by 6” wide. The blanket is placed into the trench and stapled every 1’ on the bottom of the trench.
Blankets should be laid parallel to the direction of water flow. For Category 00, 1 and 2 the netting should be on top when rolled out. For blankets with netting on 2 sides, the bottom side of the blanket should have the majority of the stitching showing.
Figure 9
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All blankets are spread evenly without stretching so that the fibers are in direct contact with the soil. Adjacent strip edges need to overlap a minimum of 4”. Strip ends need to overlap a minimum of 7” with the upgrade end on top of the downgrade end and stapled every 1.5’. For Category 00 only, the blanket should be stapled along the edges every 3’ and then watered to bond the blanket to the soil.
Figure 11
Figure 10
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When the slope length is 100’ or more, a check slot needs to be dug across the slope 1/3 from the bottom. The blanket needs to be laid in and stapled just as in the initial check slot.
The stapling pattern for the remaining portion of the blanket is shown in the following pictures depending on the application area and width of the blanket.
In winter, all snow should be removed from the area before blanket placement, and anchors substituted with 6” nails and washers.
Hydraulic Soil Stabilizers (Specifications 3884 & 2575)
Hydraulic soil stabilizers (HSS), also called HECPs (hydraulic erosion control product), are hydraulically-applied tackifiers (glues) or mulch material with a tackifier. HSS are typically used on areas with limited access or steep slopes. HSS can be used as a temporary application with or without seed, such as on stockpiles and slopes needing mulch to comply with permiting requirements. HSS can also be used
Figure 12
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for a permanent mulch application. HSS should never be used in an area with concentrated flow.
There are 4 different types of hydraulic soil stabilizers in the Mn/DOT specification. Each one has its own appropriate usage.
MaterialsSee the APPROVED PRODUCTS LIST for pre-approved products for each Type.
Type 1: Natural Tackifier Consists of water soluble natural proteins,
vegetable gums, guar gums, starch, psyllium, pitch or rosen type blended with gelling and hardening agents, or a water soluble blend of hydrophilic polymers, viscosifiers, sticking aids and other gums.
Primarily used to overspray Type 1 mulch next to the shoulder to keep the straw mulch from blowing away under traffic. Can also be used on loose soils to “set up” the soils while the vegetation is establishing.
Type 5: Hydromulch Consists of wood cellulose fibers and 2.5 to
5% of a Type 1 tackifier. Also contains a dye to ensure uniform coverage.
Primarily used in combination with Type 1 straw mulch where disc anchoring is not possible.
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Type 6: Hydromulch Blend A blend of 40 to 60% recycled paper and 40
to 60% wood cellulose fibers along with 2.5 to 5% of a Type 1 tackifier. Also contains a dye to ensure uniform coverage.
Primarily used as a temporary cover on steep slopes applied with or without seed. Can also be used as a permanent mulch in flat areas that do not have concentrated flow.
Type 8: Bonded Fiber Matrix Consists of wood or wood by-products. Contains
a minimum of 10% guar gum binder by volume and a maximum 2% crosslinker with fertilizer by volume. Also contains a dye to ensure uniform coverage.
The primary use is on inaccessible steep slopes. Seed should be applied before the application of Type 8. Type 8 is a permanent mulch cover.
Polyacrylamides A chemical able to bond soil particles temporarily
to resist erosion
InstallationAll hydraulic soil stabilizers are applied with a hydrosprayer.
Type 1: Natural Tackifier Proof of the proper application rate as indicated
by the manufacturer’s product label for the site conditions and time of year is required for each kind of Type 1 tackifier.
When used to overspray Type 1 straw mulch, apply uniformly at a rate of 200 lbs/acre or to manufacturer’s recommendations, if available.
Type 5 & 6: Hydromulch & Hydromulch Blend Mix according to the manufacturer’s directions.
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Slurry (water + mulch and tackifier) is applied at a uniform rate of 2100 lbs/acre or to manufacturer’s recommendations if available.
Applied with a flood type nozzle and 500 gallons per acre for typical uniform coverage
Type 8: Bonded Fiber Matrix (BFM) Must be applied by a manufacturer’s certified
applicator. Check for a certification card or document. Seeding should be done prior to the BFM application. BFM applications should be done on dry soils.
Water should be mixed at 100 to 125 gallons per 50 lbs of mulch material in the hydroseeder. The application rate of BFM should be 3500 lbs/acre with 100% ground coverage. The surface needs to be sprayed in two different directions to ensure soil coverage. To avoid slumping of the material, two separate applications may have to be done. The second application can occur once the surface is tacky and no longer saturated, approximately 30 minutes later. Application must occur at least 24 hours before a rainfall to allow the material to cure.
Winter HSS products applied to frozen ground are often
effective, but they should not be applied on top of snow.
Type 8 was used on this steep slope in areas where the soil washed away from underneath the blanket.
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HSS products with a curing time, such as Type 8 HSS, may not cure properly in freezing temperatures.
AcceptanceTypes 1, 5 and 6 can be accepted upon satisfactory placement.
Acceptance of acres covered by Type 8 can be made when it is evident that the seed placed has germinated and will establish an adequate protective cover. Upon proper placement of Type 8, up to 80% of the payment can be made. The remaining portion is paid upon final acceptance.
Temporary Down Drains
Temporary down drains are typically used to carry water down an un-vegetated slope. The most common location for down drains is near bridge abutments where the curb ends. The inside of superelevated curves also may benefit from a temporary down drain until vegetation has been established.
Temporary down drains are usually not included in the plan. The drains are generally added during construction when a problem area develops and the amount of runoff needs to be addressed to solve erosion and slope stability issues.
Temporary drain for inside of superelevated curve on sandy soils.
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MaterialThe pipe may be metal, plastic or flexible rubber. Depending on the steepness of the slope, riprap may be needed at the outlet to dissipate the energy.
Installation Water needs to be channeled to the inlet of the
pipe. This can be accomplished many different ways. Soil berms, sand bags, biorolls, bituminous curbs and other methods are appropriate for di-recting the water into the pipe.
The pipe needs to be secured to the slope. This can be done with wood stakes, rope or sand bags.
Provide adequate energy dissipation on the end of the pipe, i.e. blanket, riprap, a tee attached to a cross pipe.
RemovalThe temporary down drain can be removed once
Large slope drain during bridge construction.
Pipe is partially buried for temporary work road access.
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the reason for the drain is no longer necessary, i.e. permanent vegetation has established or a permanent structure has been placed to address the water issue.
Compost (Specification 3890)
Compost can be used for establishing vegetation and as an erosion control measure. Compost was historically used in landscaping areas as a soil amendment to add organic material to poor soils to help establish vegetation. The compost industry has since grown significantly and now can easily be applied hydraulically. With the hydraulic application, compost can be spread quickly and uniformly. Compost logs similar to a bioroll can also be made on site to filter water, act as a ditch check, diversion, or provide sediment control around an inlet. See the Filter Log Section for more information on the compost log.
MaterialSee Specification 3890 for complete requirements.
Grade 1 compost is derived from the decomposition of animal waste. The product shall have no offensive smell. Grade 1 is typically used as a soil amendment to help establish vegetation.
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Grade 2 compost is derived from the decomposition of leaves and yard wastes. It typically is used for landscaping and creating compost logs.
Grade 3 compost is a mixture of up to 10% Grade 1 compost with Grade 2 compost.
InstallationThe installation will depend on the application of the compost (refer to plan). For vegetaion establishment, soil loosening is required before compost application.
Erosion Stabilization Mats (Specifications 3888 & 2575)
Erosion stabilization mats, also known as turf reinforcement mats or Permanent RECPs (Permanent rolled erosion control product), are designed to reinforce vegetation. The added reinforcement allows the vegetation to withstand higher flow velocities and can be an alternative to riprap applications. Erosion stabilization mats are typically used on slope areas with concentrated flow or in channels.
MaterialsErosion stabilization mats are broken down into 5 classes based on the permissible shear stress and tensile strength. See specification 3888 for detailed requirements.
All mats consist of a 3-dimensional matrix composed of UV stabilized non-degradable synthetic fibers, filaments, nettings and/or wire mesh. The mats have cells at least 3/8” – 3/4” in depth to allow for soil filling retention.
Installation The soil needs to be prepared such that it is free
from large rocks, soil clumps or vehicle imprints
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that would keep the mat from lying flush to the surface contours.
Before placement of the mat, seeding, topsoil, and fertilizer application should be done at half of the amounts specified in the plan.
All edges of the mat should be placed in a 6” x 6” check slot and stapled every 1’. See the Erosion Control Blanket section for detailed information on check slots.
The stapling pattern should conform to a uniform 3.5 staples/yd² as shown in Figure 13.
After stapling, the mats should be directly seeded and fertilized with the remaining quantity. Screened and pulverized “Select Topsoil Borrow” should then be placed over the mat at a depth of 1/2” to 1”.
A category 4 blanket is installed on top of the mat, topsoil, seed and fertilizer matrix.
No tracked equipment or sharp turns can be made on the mat.
Std. 6.5’ mat Std. 8’ mat3.5 staples/sq. yd.
Figure 13
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SeedingEstablished vegetation is very effective at erosion control. Seeding is one of the most cost effective ways to establish vegetation, but seeding needs to be successful to achieve erosion control, and often needs temporary erosion cover until the seeds germinate and grow.
Many factors determine if a new seeding will be successful. Proper soil bed preparation, seed incorporation and adequate moisture are three keys to establishing vegetation.
The contractor needs to notify the engineer at least 24 hours in advance prior to beginning turf establishment operations to allow for inspection. To ensure a complete job, inspectors should measure the area to be seeded and the seeding contractor should be notified prior to seeding with the size of the area to seed.
Soil Bed Preparation (Specification 2575)
Immediately prior to sowing the seed, the contractor must loosen the soil to a minimum of 3” on all soils except on slopes steeper than 1:2. Some Watershed Districts require 6” of tillage. In these cases, check the special provisions or the plan for a note. Slopes steeper than 1:2 typically do not require additional tillage. Tillage can be accomplished by using disks, harrows, field diggers or other cultivating equipment. Tillage should be done at a right angle to the direction of surface flow to achieve the similar benefits of cat tracking.
Areas that are substantially compacted such as staging areas, obliterated roadways, and stockpile areas are recommended to be ripped to a minimum depth of 24”.
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Fertilizer (Specifications 3881 and 2575)
Fertilizer enhances germination and plant establishment in soils that are deficient in vital nutrients. The typical nutrients applied to the soil are Nitrogen, Phosphorous and Potassium (N-P-K).
Materials May be inorganic (salt based) or organic based
in the form of granular or granulated particles.
Contains the project’s specified percentages of N-P-K. If the N-P-K percentages are not the same yet have the same respective ratios to one another, the application rate can be modified such that the same amount of N-P-K is applied. For example, a 10-10-10 fertilizer at 100 lbs/acre was specified in the plan. The relative ratios of N-P-K are 1:1:1. The actual fertilizer applied was a 15-15-15 (same relative 1:1:1 ratios). Since the actual fertilizer contained 1.5 times more fertilizer, the application rate can be reduced by 1.5, meaning 67 lbs/acre is the equivalent application rate.
Ensure the proper type of fertilizer is applied since inorganic fertilizer and organic fertilizer react quite differently with the soil.
Type 1- Commercial Inorganic. Typically used in agricultural or lawn
care industries. A dry granulated form of N-P-K produced by mining and manufacturing.
Type 2- Phosphorous Free Inorganic. Same kind of fertilizer as Type 1
except there is no Phosphorous in the analysis.
Type 3- Slow Release Inorganic. At least 70% of the Nitrogen
component is a coated prill urea, creating the
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slow release water insoluble portion of the fertilizer.
Type 4- Natural Based Organic. A dry granulated product. A minimum of
50% of the mass and 50% of the micronutrients are derived from natural or organic material. Typically has a lower application rate and percentage of N-P-K compared to inorganic fertilizers.
Installation Fertilizer should be applied at the rate
specified in the contract before seeding using a mechanical spreading device where practical to provide a uniform distribution.
Soil should be tilled at least once within 24 hours of applying the fertilizer to ensure incorporation into the soil.
Fertilizer should not be placed on snow or frozen ground.
Seeding should take place within 48 hours of applying the fertilizer.
Lime (Specifications 3879 and 2575)
Lime is used for neutralizing soil acidity to provide better conditions for germination and plant growth.
Materials The lime material must be obtained from a
distributor or producer that is licensed from the Minnesota Department of Agriculture. A listing can be found on MDA’s web page.
The lime may be in the form of limestone (calcitic or dolomitic), burned lime, slaked lime and marl. Gypsum is not a liming product.
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The lime product must contain at least 80% Total Neutralizing Power (TNP).
The lime must have a minimum rating of 1000 lbs of ENP/ton of lime product.
The billing, invoice or ticket must include type of lime, minimum lbs of ENP/ton of lime, amount of lime supplied, and producer/customer information.
Installation Specified application rates are based on 1000
lbs ENP/ton of lime material. Actual application rates may be adjusted if the material supplied has a higher ENP rating such that 1000 lbs ENP/ton of material is applied.
Apply before seeding with a mechanical spreading device as a uniform application. Till in at least once within 24 hours of application. Lime is only effective if it is incorporated into the soil.
Seed (Specifications 3876 and 2575)
Make sure the seed is in good condition before it is seeded. It should not be wet, moldy, or partially germinated.
Check for a Certified Vendor Tag.
Check the seed tag for the proper seed species. Native seed mixtures that have MCIA origin tag species requirements are the 300’s series. If the project uses one of these mixtures, a MCIA origin tag or blanket certificate must accompany the seed stating that it is of MN origin or within approximately 1/4 the distance into a neighboring state.
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The seed tag needs to include the testing date, to be within the last 9 months, % noxious weeds (needs to be less than 2 seeds/lb), % other weed seeds, and % inert. Each species must have listed the lot number, % germination, and % purity.
Seeding (Specifications 3876 and 2575)
Seeding can be accomplished using many different types of equipment. It is always important to have a proper seedbed, uniform seed placement, an acre meter, and good seed-to-soil contact.
Seeding of Mixtures 100 – 280 (Temporary and Traditional Mixes)Seed is planted by mechanical means or hydro spreading.
Drill Seeder Preferred on heavier soils such as loams and
clays.
When operating across a slope make sure seed is being planted across the entire width of the drill and at a uniform depth.
Seed should not be planted deeper than 3/8”. Small seed species such as timothy, alfalfa, white clover, red clover, etc. shall be sown through the grass seed attachment.
If the drill does not contain a packer system, a harrow and cultipacker, or equivalent, must
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directly follow the seeder. Broadcast Seeder Preferred on sandy soils because the drill
generally sinks into the soil, planting the seed too deep.
Can be done a number of different ways: hydroseeder, mechanical cyclone seeder, or by hand.
Must look for even distribution of seed.
After seeding, the site is raked or harrowed and then firmed with a cultipacker to ensure seed-to-soil contract.
Seeding Mixtures 305 – 350 (Native Mixes) Can be seeded with a native seed drill, a drop
type seeder or a hydroseeder.
The planting rate of application must be adjusted to a total bulk rate to include the percent Pure Live Seed (PLS) in the native grasses component.
Bulk application conversion of a PLS specified seedBulk Application (lbs) = (lbs PLS) / (% PLS)
% PLS = (% Germination) x (% Purity)
Drill Seeder The drill must be equipped with disk furrow
openers and a packer assembly to compact the soil directly over the drill row. Maximum row spacing must be 8".
Seed should be planted between 1/8" – 3/8" deep.
Hydroseeder- All Seed Mixtures To obtain a more uniform distribution of seed,
a tracer of 50 lbs of Type 5 or 6 hydromulch is
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added to every 500 gallons of water in the tank.
Must have continuous agitation to keep the seed mixed in the water.
The seed must be emptied from the tank within 1 hour. After 1 hour the seed is rejected.
Interseeder Used to seed into temporary mulched areas or to
drill additional seed into previously seeded areas.
No soil tillage is necessary before this method of seeding. Mowing may be necessary before seeding.
The drill has trash rippers to slice through the vegetative mat and makes a furrow into underlying soil about 1” wide by 3/8” to 1” deep.
The drill has at least two seed boxes, a fine seed box and a box for large or fluffy seeds.
Final planting depth should be 1/4” to 3/8” for large or fluffy seeds and on the soil surface for small or fine seeds.
Mulching After Seeding On all seeded areas within 10’ of the shoulder,
the contractor must have a continuous operation to seed and immediately firm the seedbed, mulch and anchor the mulch.
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All seeded areas outside of 10’ of the shoulder must have mulch within 24 hours of seeding.
Mulch can be accepted 2 days after placement if a uniform 90% soil coverage remains.
Dormant SeedingSeeding done on exposed cold soils so that normal seed germination does not occur until the following spring. Occurs after October 20 and when soil temperatures at a depth of 1” are at or below 40 degrees.
Snow SeedingSeeding done over the top of snow so that the seed melts through the snow and germinates upon warm up in the spring. Done during the thawing days in February and March.
AcceptanceSeeding can be accepted after permanent erosion control in the area has been accepted. If mulch is delayed from seeding (it does not occur immediately within 10’ of the shoulder or within 24 hours on the remaining areas), reseeding or remulching can be ordered by the Engineer at no cost according to Mn/DOT specifications.
SodThree main types of sod are commonly used to provide an instant turf or act as instant erosion control. Lawn sod is primarily used for residential areas. Erosion control sod is used for general roadside purposes and erosion control. Salt resistant sod is used along boulevards or in potential salty environments.
Soil Bed Preparation (Specification 2575)
Soil must be loosened to a minimum depth of 3”.
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Soil must be reasonably smooth, moist and evenly textured.
Fertilizer and Lime (Specification 2575)
Fertilizer is applied prior to placing sod.
See Fertilizer and Lime sections under Seeding.
Material (Specification 3878)
Prior to delivery, the Contractor must furnish a certification from the grower stating the grass varieties contained within the sod.
All sod should consist of densely rooted bluegrass.
The top growth should be trimmed to a height of 1” to 3”.
No dry or dead edges are acceptable upon delivery.
No heating of the rolls.
Lawn Sod Lush appearance, uniform texture, bright color
throughout.
No grass blades thicker than 0.2”.
Weed free.
A blend of 4 or 5 fine-leafed turf grasses.
A minimum of 2/3 of the grasses, at the initial seeding proportions, must be an ELITE type Kentucky Bluegrass.
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Erosion Control Sod Free from noxious weeds and contains less than
3% grassy weeds, sedges, broadleaf weeds or coarse grasses.
A blend of 4 or 5 fine-leafed turf grasses.
A minimum of 2/3 of the grasses, at the initial seeding proportions, must be a LOW
MAINTENANCE type Kentucky Bluegrass.
Salt Resistant Sod Low maintenance type, fine-leafed, uniform texture.
Free from noxious, broad leafed and grass weeds.
Contains less than 3% coarse grasses.
See Table 3878-1 in the Standard Specifications for grass seed requirements.
Placement (Specification 2575)
General Before the sod is delivered, the soil bed must be
properly prepared and the Contractor must have all necessary equipment and forces available to avoid delays in placement.
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Sod strips are placed with staggered end joints and without stretching so that all ends firmly abut the edges of adjoining strips.
Joints between the sod and in place improvements such as curbs, walks and existing turf, shall abut tightly and be such that
the drainage is conducted over the surface.
The sod must be watered and compressed into the soil by rolling or tamping while laying the sod or immediately after completing the sod placement.
Slopes Strips are placed from the bottom up shingle
style and with the longitudinal axis at a right angle to the slope.
Staking or stapling may be required to prevent slumping or displacement.
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At the top of slopes steeper than 1:4, the sod is trenched 3” into the topsoil.
Ditch Bottoms The longitudinal axis of each strip is placed
parallel to the direction of water flow in the main channel.
The end of strips overlap a minimum of 4” and the side edges overlap a minimum of 3”.
The end of the upstream strip is laid on top of the downstream strip end, shingle style, to allow water to flow over, not under, the sod.
Netting material is either incorporated into the sod roots during initial growth, placed on the bottom of the sod at harvest, or Type 1 netting is secured to the ditch bottom prior to the sod placement.
Anchors • All joints and outer edges are stapled at a
maximum 3’ interval. Staples are placed throughout the sod a minimum of 2 staples per square yard.
• In ditch bottoms with intermittent flow less than 5’/sec, or when the sod is allowed to root in before carrying water, the staples are 0.12” diameter or heavier steel wire having a span width of 1” and length of 8”.
• In ditch bottoms with flows greater than 5’/sec, or when the sod is subjected to continuous flow before it roots in, the sod is overlaid with snow fence, chain link fence, jute or other biodegradable netting with a minimum life span of 3 months. The overlaid material and sod is anchored to the soil with wood stakes, 10” metal U-shape staples, or 3/16” diameter metal 10” long pins with a 1.5” steel washer.
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General Operations
Maintenance Period (Specification 2575.3 L)
Sod must be maintained for 30 calendar days.
Maintenance includes watering and replacing any sod that dries out to the point where it is presumed dead, and replacing sod that has been damaged, displaced, weakened, or weed infest-ed such that it needs replacement.
All replaced sod must be maintained for 20 cal-endar days after the replacement.
Acceptance Sod can be accepted, if in good condition, after
the maintenance period has expired.
Many additional types of construction practices occur as incidental operations with little or no plan guidance as designers do not specify the means and methods to achieve the end result. Environmental regulations, additional permits, and erosion and sediment control practices still apply even though these operations may be incidental.
Dewatering
Dewatering is defined as removal of water for construction activity in the NPDES permit. Pumping and discharging water is a common occurrence when building bridges, retaining walls, or doing any excavations near water or in rainy conditions. Any dewatering activity that exceeds 10,000 gallons per day or 1 million gallons per year requires a water appropriation permit from the Minnesota DNR. The Contractor is responsible for obtaining this permit. Remember to document your dewatering system in your plans.
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The discharge quality of the dewatering is regulated by the MPCA’s NPDES Construction permit. Discharges should be directed into a temporary or permanent sediment basin when possible. When it is not possible, other treatment measures must be used so that the discharged water does not create excess sediment into the receiving water. These treatment measures could include filtering the water through vegetation, rock, wood chips, or allowing sediments to settle out in a basin along with many other options. Flocculants can be used to speed settling times and improve filtration with some soils and waters.
Sediment trap, wood chip, and silt fence system.
To dewater this sediment basin, the contractor dug a hole and partially filled it with pea gravel. The pump sat on the pea gravel and a barrel with holes was placed on top. More gravel was placed around the side of the barrel to filter the water before it was pumped out.
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In areas of limited space, portable plastic-lined dumpsters used in conjunction with floating pumps and flocculants can act as a temporary sediment pond treatment system. The number of dumpsters is dependant on the turbidity of the treated water. The treated water should not cause a nuisance in the receiving water. Some water resources have a defined value that is acceptable, while other water resources do not. A reduction in turbidity to 50 NTUs above the background NTU level of the receiving water is often acceptable if no other quality guidance is provided.
The discharge of the dewatering should have been treated prior to being placed in a ditch system.
The discharge water is relatively the same color as the receiving water.
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Figure 14
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When discharging the water, it cannot create erosion or scour. It may be necessary to use temporary riprap, plastic sheeting, existing vegetation, or simply a longer hose to keep the discharge from creating erosion. Concrete Washout
Concrete waste materials must be disposed of in compliance with pollution control agency regulations. These wastes must not cause contamination of the ground water or surface water at the construction site before being removed for disposal. Liquids and slurry can be contained using compacted impermeable soils, impermeable plastics, or impermeable containers. Liquids may collect faster than solids and it can be more effective to pump off liquids for separate treatment and disposal from the solids. The handling process on the construction site must be identified on the site and in the construction documents.
Dewatering treatment using geotextile fabric, straw bales, and grass buffers.
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Structure Removal
While significant attention is given to protecting resources during construction of new structures and earthwork, the protection of resources during the demolition of existing structures is often overlooked. Before starting demolition of structure, think through each step of the operation and consider backup plans for the unexpected conditions. Careful planning and coordination with regulators can help get a project started off right.
Isolating the demolition activity from the environment is a common protection practice. This can be done using barriers of plastic, netting, wood, concrete, or steel depending on the nature of the demolished structure.
Dust and Airborne Particles
Airborne dust particles traveling off a construction site can contaminate surrounding water resources just as soils traveling in storm runoff. Many of the erosion
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control techniques, including good scheduling, are also effective at reducing dust, but water suppression, wind blocks, and other dust suppression agents are also options.
Chemicals, Fueling, and Hazardous Waste Handling
Chemicals, fuels, and hazardous wastes must be managed and prevented from contaminating water resources and the environment. Consult specific regulations regarding the materials, quantities, spill reporting and clean up requirements for your site. Secondary containment, onsite spill kits and procedures, and restricted access to storage are often required.
Locked containers for chemicals, in addition to spill managment kits and disposal procedures are important for clean sites.
Stockpile Protection
Stockpiles are commonly protected by silt fence or other perimeter control, or by placing the materials in a low risk location and using the material as soon as possible. However, when stockpiles become massive, perimeter control alone cannot be expected to hold back soil loss during a rain event. No matter what the size of the stockpile, perimeter control should not be placed at the immediate toe but placed at a minimum of 8’ from the toe.
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Silt fence was placed a distance from the stockpile and a vegetative buffer strip was left.
Alternatives to silt fence alone include digging a 1’ or 2’ deep trench 5’ to 10’ from the toe of the stockpile and then placing perimeter controls on the other side of the trench. The trench will help keep sediment maintenance to a minimum.
When stockpiles are in locations where space is limited, silt fence fabric wrapped jersey barriers are a good perimeter control alternative.
Soil stockpiles at a minimum should be mulched or covered to reduce erosion due to wind and rain. If stockpiles are going to remain for periods longer than 14 days, the stockpile is recommended to be seeded as soon as it is created. Some exceptions exist for non erodible materials stockpiled on site.
Street Sweeping
Street sweeping is an important housekeeping measure. When sediment is deposited onto a street by vehicle tracking or slope erosion, it needs to be
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cleaned up. Sediment left on the street can cause unsafe conditions for the traveling public. It also has to be removed for NPDES compliance. Sweeping equipment varies considerably, and consideration of the surroundings is needed when selecting the appropriate device. Common equipment and benefits are:
Dry sweeper brooms: inexpensive, but generate dust
Pick up brooms: generate less dust
Pick up broom with water and vacuum collection:good dust control and sweeping effectiveness
Pick up broom with water, vacuum collection, air recirculation and filtration: the best dust control and sweeping effectiveness. Although this is a more expensive option, it may be appropriate for high risk environments, such as adjacent to hospitals.
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Sediment Removal
Sediment removal is part of maintaining sediment control devices and cleaning up off-site sediment losses. It is required by the NPDES permit. Retrieving sediment lost off of the right-of-way also helps maintain good neighbor working relationships. Sediment removal should always be done in a timely manner to protect the environment and help facilitate good will gestures.
All sediment control devices must be cleaned out when 1/3 of the height of the device is full of sediment. A good erosion control program will greatly help reduce the amount of sediment lost off of slopes, in turn reducing the amount of necessary sediment removal.
Sensitive Area Protection
An area of the construction site may be identified as environmentally sensitive for a variety of reasons, including infiltration areas, impaired water resources, special waters, or endangered species. Communicate to everyone on the construction site where sensitive areas are located and the specific protections needed.
Areas designated for infiltration of stormwater after construction are often isolated during construction, such that no traffic, disturbance, or water can reach this area. Compaction or collection of sediments in these areas can cause the system to fail or need to be redesigned.
Areas with impaired waters, or very clean or special water often have extra restrictions specific to the resource. Consult the plan carefully for additional specific requirements in these areas. This is often true for endangered species identified near the construction site as well.
Minnesota Pollution Control Agency NPDES Construction Requirements
8/1/2008 to 7/31/2013Quick Reference Summary
See Permit MNR100001 for additional information
Reduce Erosion
Stabilize all soils within 14 days
Stabilize ditch bottoms, 200 feet back from property edge or surface water within 24 hours
Stabilize pipe outlets within 24 hours of connecting to water
Install perimeter control down gradient before disturbing any earth
Protect all storm drain inlets
Protect temporary stockpiles
Limit vehicle tracking
Water pumped off the site cannot adversely affect waters of the state
inspect the site once a week and after every 1/2 inch rainfall
Prevent pollution caused by construction waste
Erosion and Sediment Control Certification Program
Department of Bioproducts and Biosystems Engineering
University of Minnesota1390 Eckles Avenue
St. Paul, MN 55108-6005
www.erosion.umn.edu
