Erosion Control Practices

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07/12/2024 Added

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[00:00:00.090]Section 2
[00:00:00.923]of this online installer certification course
[00:00:03.030]covers erosion control practices.
[00:00:05.520]We'll cover 10 different erosion control types
[00:00:08.100]and some of the various techniques
[00:00:09.540]and practices utilized for each one.
[00:00:12.450]In this installer training section for erosion controls,
[00:00:15.150]we'll discuss the following.
[00:00:16.950]Seeding specifications for permanent, cover crop,
[00:00:20.370]and temporary types, including slope protection,
[00:00:23.100]a specific type of seeding method.
[00:00:25.350]Also, to support germination of seeding operations,
[00:00:28.410]we'll cover fertilizing and soil amendments.
[00:00:31.290]In addition, we will cover methods
[00:00:33.240]to stabilize bare soil using sodding, mulching, hydromulch,
[00:00:38.220]soil retention blankets, transition mats, silt checks
[00:00:41.700]for slopes using wattles, slope tracking,
[00:00:44.580]temporary slope drains, and soil roughening.
[00:00:48.000]First, let's review seeding and vegetation.
[00:00:50.760]Universal rules of thumb for vegetation
[00:00:52.680]would be, retain existing vegetation as long as possible.
[00:00:57.000]It's the most effective erosion control we have.
[00:01:00.120]Establish new vegetation as quickly as possible,
[00:01:03.450]and as always, minimize the amount
[00:01:05.130]of time soil is exposed on a construction site.
[00:01:08.640]Proper seed bed preparation is critical
[00:01:10.680]to the success of any type of seeding job.
[00:01:13.230]Seed bed preparation should be done
[00:01:14.910]according to the soil type
[00:01:16.590]and whether the seeding is temporary or permanent.
[00:01:19.380]Seeding will require finely-graded slopes
[00:01:21.510]and ditches that have loose soil to specify depths.
[00:01:24.660]Because of that, seeding and mulching
[00:01:26.250]should happen as soon as possible
[00:01:27.600]to minimize exposure
[00:01:28.740]of the finely-graded area to potential erosion.
[00:01:32.250]The most important aspect of any NDOT project
[00:01:35.040]is to establish vegetation as quickly as possible.
[00:01:38.490]Let's start off by discussing permanent seeding.
[00:01:41.010]This is seeding done as final grade is achieved,
[00:01:43.620]placed as part of the permanent erosion control plan.
[00:01:46.740]Permanent seeding must be done within the planting seasons
[00:01:49.230]of March 1st to June 15th and August 1st to December 1st.
[00:01:53.520]Seeding must not be done on frozen, wet, or untillable.
[00:01:56.940]We'll talk about proper seed bed preparation
[00:01:59.070]at frequent points in this section.
[00:02:01.170]For permanent seeding, surface roughening should be done
[00:02:03.630]to break up compaction of the top three inches of soil.
[00:02:06.840]Do this within five days of sowing permanent seed.
[00:02:10.200]There are two main types of permanent seeding applications
[00:02:12.720]that are done on NDOT projects,
[00:02:14.970]broadcast seeding and drill seeding.
[00:02:17.610]The site conditions and seeding selection will dictate
[00:02:20.100]which method of application will work best for the job.
[00:02:22.650]For broadcast seeding,
[00:02:23.910]a harrowing of the soil surface happens first.
[00:02:26.640]Then the seed is applied prior to any mulches
[00:02:28.860]or blankets being installed for erosion control,
[00:02:31.740]because the chances are greater for seed
[00:02:33.450]to have less than adequate soil contact and protection.
[00:02:36.780]Broadcast applications should be used
[00:02:38.520]only where equipment access is limited.
[00:02:41.220]For drill seeding, apply the seed
[00:02:42.930]with properly calibrated equipment prior to installation
[00:02:45.690]for mulches or soil retention blankets.
[00:02:48.540]In addition to the two main types described,
[00:02:50.940]NDOT specifies hydraulic seeding,
[00:02:53.220]which is only allowed in approved, special conditions.
[00:02:56.940]NDOT specifies different seed types for permanent seeding.
[00:03:00.840]Type A includes back slopes, ditches,
[00:03:03.090]and portions of the forest slopes.
[00:03:05.130]Type B includes shorter plant varieties
[00:03:07.110]placed on shoulder areas and in the medians,
[00:03:09.270]which are frequently mowed.
[00:03:11.040]Type C includes other seed mixtures
[00:03:12.870]as needed for special placement.
[00:03:14.340]For permanent seed and for each seeding type,
[00:03:16.470]we'll discuss.
[00:03:17.460]The seed bags must include NDOT seed tags.
[00:03:20.880]Bulk seed is allowed,
[00:03:22.440]but a purity and germination test is required for approval
[00:03:25.350]before the seed is used.
[00:03:27.180]The seed shall be delivered to the project
[00:03:28.980]with tags attached to the bags.
[00:03:31.230]The seed shall not be used until the project engineer
[00:03:33.750]or designated project representative
[00:03:36.060]collects the tags from the bag immediately prior to use.
[00:03:39.570]Unless this tag collection happens,
[00:03:41.250]a contractor may not be paid for seeding.
[00:03:44.280]With all seeding operations
[00:03:45.810]and particularly permanent seeding jobs,
[00:03:48.270]communication is key
[00:03:49.320]between NDOT project staff and contractors.
[00:03:52.680]Remember the specified planting seasons
[00:03:54.870]and always take the time to prepare the area
[00:03:56.970]to take the permanent seeding
[00:03:58.140]to provide optimum germination conditions.
[00:04:00.900]Permanent seeding doesn't have to wait
[00:04:02.430]until the entire project is completed.
[00:04:05.010]Permanent seeding can be
[00:04:06.420]and is encouraged to be initiated on any portion
[00:04:08.760]of a project once the final grade is achieved.
[00:04:12.060]Cover crop seeding is a type
[00:04:13.470]that is done for temporary erosion
[00:04:15.390]and sediment control while the project is still ongoing.
[00:04:19.260]Cover crop seeding is done in phased construction areas,
[00:04:22.050]surcharge areas, other disturbed areas
[00:04:24.390]that had not been permanently seeded,
[00:04:26.400]or as directed by the project manager.
[00:04:29.100]For cover crop seeding, the goal is to sow seed
[00:04:31.680]that has a good chance of establishing quickly,
[00:04:33.660]such as oats or annual rye.
[00:04:35.880]The cover crop seed selected is typically
[00:04:37.890]a rapidly-germinating variety
[00:04:40.020]used for short spurts where vegetation is needed,
[00:04:42.930]but not for an extended period of time.
[00:04:45.510]For finished grades, cover crop seeding needs
[00:04:47.820]to be started within 24 hours
[00:04:50.010]and completed within seven days
[00:04:51.450]of finish grading work.
[00:04:52.650]For cover crop seeding, there are early season,
[00:04:55.350]mid-season, and late season mixes available
[00:04:58.650]from oats and millet in the spring
[00:05:00.300]and early summer to winter wheat in the fall.
[00:05:03.330]Annual ryegrass applied only in urban areas
[00:05:05.940]is available year round.
[00:05:07.920]Also, note that broadcast
[00:05:09.510]and drill seeding application rates
[00:05:11.130]are the same For cover crop seeding.
[00:05:12.870]Is the placement of cover crop seed alone
[00:05:14.790]considered stabilization?
[00:05:16.680]No.
[00:05:17.513]However, once it's germinated and established,
[00:05:20.250]cover crop seeding provides
[00:05:21.570]the same short-term effect as permanent vegetation.
[00:05:24.660]It's an important distinction to make,
[00:05:26.250]as the State Of Nebraska's construction general permit
[00:05:29.130]requires the initiation of temporary stabilization
[00:05:31.710]of exposed soils exposed for 14 days
[00:05:34.110]or more due to site and activity.
[00:05:36.330]This is required even if site will be temporarily inactive.
[00:05:39.870]Seeding alone doesn't achieve this until it's established.
[00:05:43.020]At a minimum, when soil and weather conditions exist,
[00:05:45.570]that it's anticipated that the cover crop seed
[00:05:47.700]will not germinate within 10 calendar days,
[00:05:49.860]the project manager or her construction engineer
[00:05:52.290]will direct the temporary mulch be applied.
[00:05:55.080]If it fails to germinate
[00:05:56.310]or produce vigorous growth,
[00:05:58.050]reseeding shall be required at the contractor's expense.
[00:06:01.830]Temporary seeding consists of furnishing
[00:06:03.810]and applying seed to soil that would be difficult
[00:06:05.940]to seed using broadcast or drill seeding methods.
[00:06:09.120]Temporary seeding requires hydroseeding,
[00:06:11.670]a technique we will discuss in a little bit.
[00:06:14.100]Temporary seeding can be used on embankments
[00:06:16.230]or cuts that are temporary in nature,
[00:06:18.270]soil stockpiles and other places that require stabilization.
[00:06:22.080]The work of temporary seeding shall be started
[00:06:24.030]within 24 hours and completed within seven calendar days,
[00:06:27.180]following earth-moving activities.
[00:06:30.000]Fertilizer may be specified on certain seeding projects,
[00:06:33.270]primarily for permanent seeding.
[00:06:35.490]These may be synthetic, organic,
[00:06:37.080]or inorganic fertilizers,
[00:06:39.120]fertilized prior to seeding and worked into the soil.
[00:06:42.150]Payment for fertilizing is subsidiary
[00:06:43.980]to items requiring fertilization.
[00:06:46.860]For application of fertilizers,
[00:06:48.510]apply uniformly with approved mechanical spreaders
[00:06:51.060]at rates specified in the project contract.
[00:06:53.940]Do not apply fertilizers within 50 feet
[00:06:55.980]of any wetland, lake, or stream.
[00:06:58.740]For soil incorporation with permanent seeding,
[00:07:01.470]fertilization application should happen
[00:07:03.240]prior to seeding.
[00:07:04.530]In conjunction with any seed, be prep work,
[00:07:07.110]but should not be worked into the soil
[00:07:08.790]any deeper than three inches.
[00:07:10.230]Soil amendments are a new specification for NDOT
[00:07:13.590]and generally refer to products
[00:07:15.000]known as hydraulic growth mediums.
[00:07:17.310]These products are made from a combination of ingredients
[00:07:19.680]for improving poor soil conditions such as processed straw,
[00:07:23.460]flexible flax fibers, peat moss, plant root fungi,
[00:07:26.940]and other proprietary ingredients.
[00:07:28.740]These particular soil amendments may be specified
[00:07:31.320]for permanent seeding projects.
[00:07:33.450]When specified, drill half of the seed required
[00:07:35.730]per acre of the project area,
[00:07:37.650]then apply the other half of the required seed
[00:07:39.600]by incorporating into the soil amendment slurry.
[00:07:42.660]Apply within 24 hours of seed planting
[00:07:45.030]and uniformly over the prepared area
[00:07:46.920]at an application rate of two tons per acre.
[00:07:50.280]Sodding is treated as a permanent erosion control
[00:07:52.590]providing instant coverage on exposed soils,
[00:07:55.320]making it one of the most effective
[00:07:56.820]erosion controls available.
[00:07:58.830]Sodding involves laying a continuous cover
[00:08:00.900]of grass sod on exposed soils.
[00:08:03.990]With sodding installations,
[00:08:05.760]watering is required for 30 days after insulation.
[00:08:09.030]If it's not green and healthy
[00:08:10.470]after 30 days, it should likely be rejected
[00:08:12.660]and reinstalled by the contractor,
[00:08:14.760]which must also be watered for 30 days.
[00:08:17.580]In this example, the sod is not only very brown,
[00:08:20.700]signaling a lack of moisture,
[00:08:22.530]but it also has large cracks between the sod strips.
[00:08:25.710]This installation should likely be rejected
[00:08:28.230]and the contractor should be forced
[00:08:29.670]to reinstall new sod at their own expense.
[00:08:32.610]Soil amendments may also need
[00:08:34.110]to be considered if the soil the sod is being installed
[00:08:37.200]into is poor or lacking organic content.
[00:08:40.830]Next, let's move on to mulching.
[00:08:43.080]As we discussed briefly in the previous module,
[00:08:45.660]the purpose of erosion control
[00:08:47.190]is to prevent the erosion process from beginning,
[00:08:49.890]starting with protecting the soil surface
[00:08:51.780]from the impact of raindrops.
[00:08:53.910]Mulching covers the soil surface, reducing rainfall impacts
[00:08:57.330]and helps to absorb and hold moisture near the surface.
[00:09:00.750]Applied after seeding,
[00:09:02.130]mulch protects the seed underneath
[00:09:03.750]during the germination process.
[00:09:05.880]When used alone, it temporarily protects the soil surface
[00:09:08.790]between specified planting seasons per NDOT specifications.
[00:09:12.990]Acceptable mulch types include
[00:09:15.240]dry cured native prairie hay,
[00:09:17.010]native grass hay, and straw from oats, wheat or rye.
[00:09:21.240]NDOT does not accept the following mulch materials:
[00:09:24.750]Broome hay, rushes, cattails, reed canary grass,
[00:09:28.830]wide-bladed grass or any invasive species.
[00:09:32.040]All mulch must be certified noxious
[00:09:34.110]and or weed-free by a county weed authority
[00:09:36.150]or other approved agent.
[00:09:38.490]An important skill for an installer
[00:09:40.110]is to visually confirm the proper mulching application rate.
[00:09:43.530]Here we have four examples of coverage
[00:09:45.300]with a corresponding application rate.
[00:09:47.700]Typically, the installation specification
[00:09:49.710]will be for a rate of two tons per acre.
[00:09:52.290]At that application rate,
[00:09:53.610]it should be very difficult to see any soil surface
[00:09:56.040]as you're looking down at any given location.
[00:09:58.740]More than likely, you will see application rates
[00:10:00.840]less than at two tons per acre.
[00:10:03.210]Whether it is an installation problem
[00:10:04.920]or due to windy conditions
[00:10:06.150]that may have blown some of the mulch away,
[00:10:08.280]make sure to note
[00:10:09.113]whether or not you believe the proper application rate
[00:10:11.400]was used when you were conducting
[00:10:12.810]or observing the installation.
[00:10:14.250]Specifications will also require proper crimping
[00:10:16.890]of the straw mulch into the soil,
[00:10:18.450]typically to a one-to-two inch depth.
[00:10:20.820]Look for mulch fibers
[00:10:21.900]that have been driven into the ground deep
[00:10:23.490]and stand almost vertical in places.
[00:10:26.250]In lieu crimp straw mulch,
[00:10:28.230]a tackifier and bonded fiber matrix
[00:10:30.540]may be specified in some places.
[00:10:32.940]We'll talk more about those examples coming up.
[00:10:35.640]Most importantly, to ensure good consistent coverage,
[00:10:38.640]an installer should avoid applying straw mulch
[00:10:40.770]in windy conditions if at all possible.
[00:10:43.950]Even in one project area,
[00:10:45.780]we can have the potential for inconsistent cover traits.
[00:10:48.960]The area in the foreground looks
[00:10:50.310]to have good consistent coverage.
[00:10:52.530]As we progress further into the project,
[00:10:54.810]the coverage becomes more inconsistent,
[00:10:57.150]with only a very thin mulch layer in the distance.
[00:11:00.120]Consistency with the mulch layer
[00:11:01.980]following the mulch density to the specification
[00:11:04.200]as close as possible is what we are looking for.
[00:11:07.860]Slope protection refers to a specific type
[00:11:10.110]of installation combination of placing seed
[00:11:12.270]and a protected covering of mulch on completed shoulders,
[00:11:15.000]side slopes, ditch bottoms, or back slopes.
[00:11:18.120]Straw is not allowed for this application.
[00:11:20.760]Initial seed should be drill seeded if possible,
[00:11:23.460]with the remainder broadcast over the installed mulch.
[00:11:26.400]Secure the mulch with either a specialized punch roller
[00:11:29.400]or with evenly-spaced soil piles, per the specification.
[00:11:33.780]The next erosion control practice
[00:11:35.490]we'll discuss is hydromulch.
[00:11:37.440]These versatile products are wet applications
[00:11:39.570]of a combination of seed
[00:11:40.770]and/or mulch sprayed onto the soil surface.
[00:11:43.800]They protect previously-planted seabeds
[00:11:45.780]on slopes and roadsides, covering the soil's surface
[00:11:48.750]to reduce erosion from rainfall impacts.
[00:11:51.540]Like straw mulch, they retain moisture at the soil surface.
[00:11:55.080]Some products are used to anchor mulch
[00:11:56.880]to the soil surface when crimping is prohibitive.
[00:11:59.910]Some of these types of hydraulic applications
[00:12:02.100]can also protect exposed
[00:12:03.450]areas where sheet flows tend to occur.
[00:12:06.540]There are many different compositions of hydromulch.
[00:12:09.300]Locations to apply hydromulch vary by grade, soil type,
[00:12:13.020]stage of construction,
[00:12:14.580]combination with other BMPs,
[00:12:16.560]desired conditions, and chemical composition of materials.
[00:12:20.310]They provide immediate protection from wind and rain
[00:12:23.040]and provides more time for vegetation to establish.
[00:12:26.760]Hydraulic mulches are typically specified in four classes
[00:12:29.760]for NDOT projects.
[00:12:31.710]Class HM1 is either a dry or wet pelletized mulch.
[00:12:35.370]These are used in confined and completely flat areas.
[00:12:38.700]Class HM2 is wood fiber mulch with a tackifier.
[00:12:42.240]This application works for gentle slopes,
[00:12:44.220]3.5 to one or less.
[00:12:46.410]It's not accepted to use in ditch applications,
[00:12:48.960]and the lifespan for the application is about three months.
[00:12:52.410]Allow for 24 hours of precipitation
[00:12:54.600]for curing time for the mulch to set.
[00:12:57.120]For bonded fiber matrix or class HM3,
[00:13:00.180]the product is allowable
[00:13:01.410]on slopes 2 1/2 to one or less.
[00:13:04.200]BFM longevity is typically up to six months
[00:13:07.140]and also requires 24 hours of dry curing time.
[00:13:10.740]For fiber reinforced matrix,
[00:13:12.720]the product is allowable on slopes 1 1/2
[00:13:14.957]to one or less and in ditches with a slope of 2.5% or less.
[00:13:19.890]FRM longevity is 12 months minimum
[00:13:22.590]and has little to no curing time,
[00:13:24.660]meaning it's ready to hold up
[00:13:25.770]to precipitation as soon as it's applied.
[00:13:28.590]All application rates for hydromulch are 1.5 tons per acre.
[00:13:32.430]There are two ways to apply hydromulch.
[00:13:34.710]The most effective way to ensure adequate
[00:13:36.600]and uniform material coverage is by using the hose.
[00:13:39.870]An applicator sprays the material
[00:13:41.520]down over an accessible area
[00:13:43.440]and is able to achieve uniform coverage.
[00:13:45.990]The most efficient application method
[00:13:47.610]is by using the gun or turret,
[00:13:49.530]located on the back of larger hydromulch equipment.
[00:13:52.740]While this application method can be more efficient,
[00:13:55.470]it doesn't always provide the best application
[00:13:57.570]to ensure uniform coverage.
[00:13:59.760]As a rule of thumb,
[00:14:01.200]if you're able to access the treatment area
[00:14:03.090]with the hose, by all means, use it.
[00:14:06.450]Visual confirmation of full mulch coverage
[00:14:08.430]is essential to the success or failure of an application.
[00:14:11.820]In this example, it's obvious to see the direction
[00:14:14.220]that hydromulch was shot from was left to right
[00:14:16.200]from the back of the machine and not with the hose.
[00:14:19.410]From the applicator's perspective,
[00:14:21.360]it may very well have looked like 100% coverage.
[00:14:24.570]Seeing from the side here,
[00:14:26.070]we can see that the application
[00:14:27.450]had a shadowing effect as it hit the soil surface.
[00:14:30.450]If using the gun or turret,
[00:14:32.370]do everything you can to apply the hydromulch
[00:14:34.530]in two directions if at all possible.
[00:14:37.380]This will ensure an even coverage.
[00:14:39.090]Hydromulch can also be used for rapid stabilization
[00:14:41.790]when work has stopped for a period of time
[00:14:43.530]in certain areas of a project.
[00:14:45.780]These slopes aren't ready for permanent erosion control
[00:14:48.270]to be installed, but still pose
[00:14:50.280]a significant threat for real ankle erosion.
[00:14:53.400]Applying bonded fiber matrix to provide stabilization
[00:14:56.250]for a period of time is an effective control.
[00:14:59.520]Visual confirmation of uniform
[00:15:01.260]and full application is required.
[00:15:03.480]If you can still see exposed soil
[00:15:05.040]after application, you can be sure
[00:15:07.110]you haven't met the installation specification.
[00:15:09.720]Remember, for all mulch types,
[00:15:11.430]the application rate is 1.5 tons per acre.
[00:15:15.240]Soil retention blankets have been in use
[00:15:17.220]for many decades on construction sites for erosion control.
[00:15:20.820]Blankets cover the soil surface
[00:15:22.380]to reduce erosion from rainfall impact.
[00:15:25.140]Depending on the product type,
[00:15:26.610]they also prevent soil erosion
[00:15:28.470]in high velocity drainage areas.
[00:15:30.690]Soil retention blankets are typically used in conjunction
[00:15:33.570]with temporary or permanent seeding,
[00:15:35.730]covering a seeded area,
[00:15:37.410]preventing the movement of the planted seed.
[00:15:39.630]They can absorb and hold moisture near the soil surface.
[00:15:43.440]Different projects with different slopes
[00:15:45.090]and conditions will dictate the different types
[00:15:47.010]of soil retention blankets that are used on a site.
[00:15:50.010]Projects will use any mixture of materials
[00:15:51.990]to get the job done right.
[00:15:53.790]Products are not interchangeable
[00:15:55.230]because they're specified as an engineered product
[00:15:57.450]for the design condition.
[00:15:59.070]For example, a Class 1D straw blanket
[00:16:01.470]would not be used in a high flow area
[00:16:03.270]such as a ditch bottom.
[00:16:04.890]A heavier duty Class 1 or 2 blanket
[00:16:06.930]would be the proper product in a ditch bottom.
[00:16:09.870]While there are many NDOT specification types
[00:16:12.480]for soil retention blankets,
[00:16:14.310]the primary makeup for Class 1 include
[00:16:16.770]straw, coconut, fiber, and wood excelsior fiber.
[00:16:19.980]Some blanket types may also include
[00:16:21.810]a combination of straw and coconut fiber.
[00:16:24.690]Also, the blanket netting may vary with certain types.
[00:16:27.870]A biodegradable nylon netting is common,
[00:16:30.510]but natural jute or twine fiber netting
[00:16:32.460]is also used for certain Class 1 blankets.
[00:16:35.340]The lifespan of Class 1 blankets is anywhere
[00:16:37.530]from six months to three years depending on the type.
[00:16:40.726]Class 1 blankets are used on slopes
[00:16:43.020]and hillsides with a slope steepness of up to three to one.
[00:16:46.200]They can also be used in shallow, low-slope ditches
[00:16:49.080]where concentrated runoff velocities are low.
[00:16:52.230]Different blanket types
[00:16:53.280]have different installation staple patterns.
[00:16:55.890]Be sure to follow NDOT specifications for each blanket type.
[00:17:00.630]Once we cross over into mostly synthetic materials
[00:17:03.300]that make up a blanket,
[00:17:04.890]we are referring to Class 2 blankets
[00:17:07.200]built for permanent, long-term ditch stabilization.
[00:17:11.070]They can be a combination of synthetic
[00:17:12.720]and biodegradable materials
[00:17:14.790]or be composed of 100% synthetic material.
[00:17:18.210]Because of their higher cost,
[00:17:19.830]they aren't typically used on side slopes.
[00:17:22.410]The sturdy nature of these blankets support
[00:17:24.300]greater root growth media
[00:17:25.500]and root structure compared to simply bare soil
[00:17:28.380]or a material that fully biodegrades.
[00:17:31.530]This cross-sectional view
[00:17:32.760]of a turf reinforcement map shows the growth media
[00:17:35.280]in the middle, protected root growth
[00:17:37.020]and vegetation reinforcement.
[00:17:39.300]The key here is that the material
[00:17:40.770]is laid smoothly against the soil surface.
[00:17:43.740]Any gaps between the fabric material
[00:17:45.870]and the soil surface will promote scour under the material.
[00:17:49.890]Quick selection guides located
[00:17:51.540]in the NDOT Erosion and Sediment Control Pocket Guide
[00:17:54.570]will identify the proper product selection
[00:17:56.520]for the type of area you are treating.
[00:17:58.800]There is a selection chart for both slope erosion control
[00:18:01.860]and ditch and channel erosion control.
[00:18:04.830]As we have talked about previously,
[00:18:06.390]proper seed bed preparation is critical
[00:18:07.937]of the success or failure of a blanket installation.
[00:18:11.550]In this example, we can see where we have specific spots
[00:18:14.640]where blanket has been installed
[00:18:15.960]over larger clods of dirt that were not prepped correctly.
[00:18:19.320]These clods tend the blanket,
[00:18:20.730]leaving void spaces underneath the blanket,
[00:18:23.220]which can lead to rills and gully erosion
[00:18:25.110]underneath the blanket,
[00:18:26.070]resulting in poor vegetated establishment.
[00:18:28.860]As described earlier,
[00:18:30.060]proper seed bed prep means
[00:18:31.500]that we can have excellent mat-to-soil contact.
[00:18:34.620]A blanket application
[00:18:35.730]needs to have great soil contact over the entire area.
[00:18:39.870]For slope applications,
[00:18:41.370]the blanket attachment at the top of the slope is important.
[00:18:44.640]Folding the blanket under the soil,
[00:18:46.230]stapling in place, then compacting the soil
[00:18:48.600]over the top of the attachment ensures
[00:18:50.280]that sheet flows do not flow under the blanket
[00:18:52.410]at the top of the slope.
[00:18:54.150]Beginning the erosion process under the blanket.
[00:18:57.120]Folding the top six inches of blanket together
[00:18:59.760]and installing a double row
[00:19:00.990]of staples closed together
[00:19:02.310]across the entire edge is also accepted.
[00:19:05.640]The critical success factor
[00:19:06.960]for any blanket installation
[00:19:08.370]is proper attachment to the ground.
[00:19:10.650]This is done with staples.
[00:19:12.360]For each installation type,
[00:19:13.830]there is a corresponding staple pattern to use.
[00:19:16.620]Contractors use different methods for installing staples,
[00:19:19.860]but it is universal that the staple pattern
[00:19:21.810]for each blanket type be followed as a minimum measure.
[00:19:25.110]Any chance that you can utilize
[00:19:26.430]more staples to ensure uniform mat-to-soil contact
[00:19:29.280]will make the blanket installation much more effective.
[00:19:32.460]For staple patterns and additional information,
[00:19:35.100]refer to NDOT Standard Plan 501.
[00:19:39.090]Failing to follow the NDOT specification
[00:19:41.580]for staple patterns is a good way to invite erosion
[00:19:44.010]to occur when material gets loose.
[00:19:46.410]Failing to staple a blanket correctly
[00:19:48.240]can lead to quick detachment
[00:19:49.500]by even moderate windy conditions.
[00:19:51.840]This installation may keep unraveling
[00:19:53.670]if not quickly repaired,
[00:19:55.380]leading to a complete reinstallation.
[00:19:57.150]When determining if your blanket installation
[00:19:59.220]meets NDOT specifications,
[00:20:01.740]here's a few recommended observations to make.
[00:20:04.740]One, look for proper staple placement.
[00:20:07.830]With each type of blanket,
[00:20:09.300]there is a corresponding staple pattern
[00:20:11.100]which must be followed.
[00:20:12.810]Blankets installed in swales
[00:20:14.250]or ditches need more staples to keep the blanket in place.
[00:20:17.580]Two, lift the blanket
[00:20:19.380]to check if staples were installed correctly.
[00:20:22.050]If the blanket is easily pulled away from the soil surface,
[00:20:25.020]it likely needs more staples placed to secure it in place.
[00:20:28.620]Use the required staple patterns as a minimum.
[00:20:31.440]Don't skip, because a blanket failure
[00:20:33.690]can happen easily underneath if improperly installed.
[00:20:37.140]Three, if the installation has been done in a ditch
[00:20:39.840]or swale, verify that staple check slots have been installed
[00:20:43.860]and the blanket edges were properly secured.
[00:20:46.740]Four, finally, verify the staple sizes
[00:20:49.620]to the required specification.
[00:20:52.260]Outlet protection can be composed
[00:20:53.880]of rock riprap, Class 2 soil retention blankets,
[00:20:57.270]transition matting and/or sod.
[00:21:00.180]Outlet protection minimizes scour at the pipe outlet.
[00:21:03.540]These materials and techniques
[00:21:04.980]can be used at outlets of pipes,
[00:21:06.540]drains, culverts, slope drains, diversion ditches,
[00:21:09.900]swales, conduits, or channels.
[00:21:13.350]Riprap outlet protection is made of coarse rock material,
[00:21:16.890]commonplace on many construction sites
[00:21:18.780]for stabilizing channels and basins.
[00:21:21.270]The size of riprap material is specified
[00:21:23.430]based on the anticipated flow characteristics
[00:21:25.650]of the outlet, designed and specified by an engineer.
[00:21:30.390]Other approved products
[00:21:31.470]and specifications for outlet protection
[00:21:33.510]are transition mats.
[00:21:35.190]The first is a lightweight product,
[00:21:36.810]which doesn't need heavy equipment for installation.
[00:21:39.630]These are an alternative to rock riprap
[00:21:41.430]that promotes grass and vegetation to grow up
[00:21:43.950]through the open spaces in the matting,
[00:21:46.140]creating a hard, armor-like bottom, but easier to maintain.
[00:21:50.070]Be sure to follow the manufacturer's specifications
[00:21:52.350]when installing transition mats.
[00:21:54.000]Another new type of transition mat
[00:21:55.710]is a tiled concrete block mat,
[00:21:57.660]which is a vegetated concrete block mat
[00:21:59.580]utilized for stabilizing slopes,
[00:22:01.620]channels, low water crossings,
[00:22:03.810]inlet and/or outlet protection and shorelines.
[00:22:07.110]It consists of concrete blocks locked together
[00:22:09.390]and embedded into a high strength geogrid.
[00:22:12.120]There is 1.5 inch spacing between the blocks
[00:22:14.610]that gives the mat flexibility
[00:22:16.380]and allows for optional vegetation growth.
[00:22:19.080]The mat is packaged in rolls,
[00:22:20.700]making transporting and installing efficient.
[00:22:22.830]For all types of outlet protection,
[00:22:24.870]the most important installation keys
[00:22:26.430]are to follow all engineering plans
[00:22:28.080]and specifications for the project
[00:22:30.270]and understand where drainage needs to go.
[00:22:32.730]If stormwater drainage
[00:22:33.900]is able to find an easier path, it will.
[00:22:36.870]Don't allow water to flow anywhere
[00:22:38.370]other than through the outlet protection.
[00:22:41.070]Let's discuss silt checks, utilizes slope interruptions.
[00:22:44.580]These essentially act as speed bumps
[00:22:46.290]for runoff on longer forest slopes or back slopes,
[00:22:49.920]dissipating the energy of storm water flows,
[00:22:52.650]thus decreasing the potential and severity of erosion.
[00:22:55.980]Silt checks on slopes are selected
[00:22:57.810]or specified for slopes longer than 50 feet
[00:23:00.780]and temporarily support vegetative growth
[00:23:03.330]so slopes can achieve final stabilization requirements.
[00:23:06.210]The key to installing silt checks for slope interruptions
[00:23:08.910]is to make sure they're installed exactly on the contour.
[00:23:12.360]In this example, we see a string
[00:23:14.460]being used to mark the contour.
[00:23:16.530]Any slope or angle
[00:23:17.580]to the interruption will potentially cause a point
[00:23:19.620]of concentration, causing a rile or gully to form.
[00:23:23.280]For silt check installation
[00:23:24.570]in conjunction with a blanket application,
[00:23:26.880]stake the silt check on the downstream side.
[00:23:29.490]Stake at two foot intervals.
[00:23:31.980]Proper spacing is a critical success factor
[00:23:34.170]for installing slope interruptions.
[00:23:36.480]Almost without exception,
[00:23:38.220]long slopes will specify
[00:23:39.660]a 12-inch diameter wattle to be installed.
[00:23:42.360]For typical three to one slopes,
[00:23:43.950]spacing between each interruption will be 25 feet.
[00:23:47.820]Another form of a slope interruption
[00:23:49.470]would be vertical slope tracking,
[00:23:51.390]done by creating a ground disturbance
[00:23:52.980]with a dozer with sizable tracks,
[00:23:55.290]driving up and down a slope in a vertical motion,
[00:23:57.990]creating horizontal impressions,
[00:23:59.970]essentially mini terraces.
[00:24:01.980]This technique can be used in conjunction
[00:24:03.900]with other BMPs such as seeding, mulch, or hydromulch.
[00:24:07.650]Slope tracking is paid for by square yard.
[00:24:10.980]Just by tracking a slope vertically with the right piece
[00:24:13.440]of equipment, the erosion potential
[00:24:15.360]can be cut by 50% on a three to one slope.
[00:24:18.420]That's a tremendous improvement over doing nothing
[00:24:20.520]with an impending rain forecast, 24 to 48 hours out.
[00:24:24.210]It also gives a slope decent preparation
[00:24:26.190]to install cover crop seeding,
[00:24:28.170]as the small impressions capture
[00:24:29.880]and hold the seed in place,
[00:24:31.590]allowing for better germination potential.
[00:24:34.620]In this example,
[00:24:35.820]the slope has been fine-graded horizontally.
[00:24:38.640]The cat tracks create express lanes for runoff
[00:24:40.980]to run downhill, gathering speed, causing rile erosion,
[00:24:45.180]and eventually gullies.
[00:24:46.980]Whenever possible, take advantage
[00:24:48.480]of the erosion control benefits of vertical slope tracking.
[00:24:51.330]The last erosion control BMP
[00:24:53.760]we will review is a temporary slope drain.
[00:24:56.430]This work consists of constructing
[00:24:57.900]a slope drain with any type of new or used
[00:25:00.750]rigid or flexible pipe
[00:25:02.400]that will adequately carry collected stormwater
[00:25:04.620]from the toe of slope
[00:25:05.580]to the ditch to prevent erosion on the slope.
[00:25:08.310]Temporary slope drains should be sized
[00:25:10.170]according to the amount of anticipated runoff
[00:25:12.090]from the drainage area.
[00:25:13.830]These drains shall be securely anchored
[00:25:15.600]at the inlet, outlet, and along the slope
[00:25:18.540]and velocity dissipation shall be placed
[00:25:20.580]at the slope drain outlet to prevent scour.
[00:25:22.770]Soil roughening is the practice of creating parallel strips
[00:25:25.590]of rough soil for erosion control purposes.
[00:25:28.560]These strips of roughened soil
[00:25:29.940]can act is a slope eruption,
[00:25:31.950]slowing down velocities of runoff water
[00:25:33.990]on the contours of slopes or cross ditch bottoms.
[00:25:37.080]They're made by using a field cultivator
[00:25:38.880]or disk to make roughened areas
[00:25:40.410]a minimum of eight feet wide,
[00:25:42.090]at a minimum of three inches deep.
[00:25:44.220]This work shall be initiated when the finish grade
[00:25:46.440]is established for any location designated
[00:25:48.329]in the contract for soil roughening.
[00:25:50.910]It may also be used when work stops
[00:25:52.650]for a period of time after locations have been rough graded.
[00:25:56.490]Wrapping up Section 2,
[00:25:57.660]we covered a lot of ground.
[00:25:59.520]You should have a better understanding of NDOT specification
[00:26:02.550]and installation requirements
[00:26:03.900]for seeding and fertilizing methods
[00:26:05.970]and soil stabilization methods like mulching, hydromulch,
[00:26:09.480]soil retention blankets, outlet protection,
[00:26:12.750]including rock riprap, and transition mats, silt checks
[00:26:15.720]for slopes using wattles,
[00:26:17.430]slope tracking, temporary slope drains, and soil roughening.
[00:26:21.840]Now, close the slideshow and return to the course menu
[00:26:24.480]and take the quick five question quiz
[00:26:26.130]to move on to Section 3.

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Erosion Control Practices

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