NDOT Erosion Sediment Control Inspector Re-Certification Section 3 Part 1

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09/25/2020 Added

722 Plays

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This video is Section 3 (Part 1) in a series of 5 videos

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[00:00:00.730]Now let's get familiar
[00:00:02.080]with common examples and considerations
[00:00:04.168]that will be part of implementing and updating
[00:00:06.850]a temporary erosion and sediment control plan
[00:00:09.550]on an NDOT permitted construction project.
[00:00:14.230]Remember, as we conduct this virtual walkthrough
[00:00:16.690]of a project, we are always approaching situations
[00:00:19.568]from the standpoint of managing environmental risk.
[00:00:23.530]As you walk the site assessing conditions,
[00:00:26.020]remember to consider; is the project in compliance
[00:00:29.350]with the state construction general permit?
[00:00:32.230]Do I understand the potential cost of noncompliance?
[00:00:36.060]And have BMP's been selected, installed
[00:00:39.660]and maintained correctly?
[00:00:43.610]And this is another logical time to remember
[00:00:46.090]the concept of our temporary erosion
[00:00:48.320]and sediment control plan as an adaptive management process,
[00:00:52.550]constant review and assessment
[00:00:54.510]and implementation of practices throughout
[00:00:56.570]the life of a project that keeps us in compliance,
[00:00:59.600]keeping erosion to a minimum and sediment contained onsite
[00:01:02.630]as much as possible.
[00:01:04.560]Now we will effectively assess site conditions,
[00:01:07.480]determining what BMPs are needed,
[00:01:09.710]as well as assessing the effectiveness
[00:01:11.440]of practices already installed.
[00:01:14.020]Inspections lead to implementing corrective actions
[00:01:16.860]or installing or repairing best management practices,
[00:01:20.050]then assessing their effectiveness.
[00:01:22.160]And the process of adaptive management repeats
[00:01:25.440]for the life of the project.
[00:01:28.670]But before we head out onto the project
[00:01:30.630]and get our shoes muddy, we should have a good understanding
[00:01:33.240]of what tools we have in our temporary erosion
[00:01:35.458]and sediment control BMP toolbox.
[00:01:39.010]As well as understand what construction phases
[00:01:41.370]are happening when.
[00:01:44.510]At the beginning of a project and at the start of
[00:01:46.880]each new phase of construction within a project,
[00:01:49.710]these are perfect times to review the project's
[00:01:52.330]summary of quantities, a part of the project plan set.
[00:01:56.750]We'll highlight three of the groups.
[00:01:58.930]Group one, grading items.
[00:02:01.470]Group five, seeding items.
[00:02:04.260]And group 10, general items.
[00:02:08.690]Under group 10 or general items in the summary
[00:02:11.510]of quantities, you'll find quantities
[00:02:13.520]for temporary erosion and sediment control BMPs
[00:02:16.340]estimated by the designer.
[00:02:18.590]This is the starting point for SWPPP implementation teams
[00:02:21.568]to consider the types of temporary BMPs
[00:02:24.349]they should place on a project and gain a good understanding
[00:02:28.040]as to what the designer took into consideration
[00:02:30.440]for practical BMPs and quantities
[00:02:32.589]they felt would be expected during the construction process.
[00:02:37.330]Again, this is a starting point.
[00:02:39.560]Factors like an unseasonably wet weather pattern
[00:02:42.229]could mean the need for more temporary BMPs
[00:02:45.840]than what was initially planned.
[00:02:49.820]Group one or grading items, contains quantities
[00:02:54.010]for the permanent erosion and sediment controls
[00:02:55.869]which were designed into the permanent erosion
[00:02:58.670]and sediment control plan.
[00:03:00.910]The BMP quantities in group one correspond
[00:03:03.246]with the tabulated quantities shown
[00:03:05.790]on the permanent plan sheets.
[00:03:08.490]These practices are to be implemented
[00:03:10.100]at either the end of the construction phase of a project,
[00:03:13.296]or as a particular phase of the project is completed.
[00:03:19.020]Group five is seeding items, identifying quantities
[00:03:22.738]of each type of seeding to be done during the project.
[00:03:28.270]Another thing to remain familiar with
[00:03:29.820]during the life of the project is the construction schedule.
[00:03:33.360]Understanding what phase or phases of the project
[00:03:36.520]are wrapping up and what is upcoming.
[00:03:39.530]This may be a factor in temporary erosion
[00:03:42.100]and sediment control considerations
[00:03:44.190]as you assess situations in the field.
[00:03:47.060]Remember implementing effective erosion
[00:03:49.100]and sediment control isn't just an activity reserved
[00:03:51.810]for the end of our project.
[00:03:53.880]Our responsibility is for limiting erosion
[00:03:56.210]and offsite sedimentation as much as possible
[00:03:58.920]throughout the life of the project.
[00:04:02.350]So, here are the eight different site assessment scenarios
[00:04:06.000]we'll review in this section and the considerations
[00:04:08.680]we must factor in for each one.
[00:04:11.690]Think of this as one big walkthrough
[00:04:14.290]of an NDOT construction project, conducting an inspection.
[00:04:18.670]Along the way we'll make site assessment considerations
[00:04:22.110]for the following; protecting discharge locations
[00:04:26.050]or perimeter controls, stabilizing inactive areas,
[00:04:30.930]stabilizing inactive slopes, stabilizing ditches
[00:04:35.360]and conveyances, sediment containment systems,
[00:04:39.990]concentrated flow management, channel crossing management,
[00:04:44.420]and finally dewatering practices.
[00:04:49.350]So let's begin our inspection and site assessment
[00:04:52.080]by protecting discharged locations.
[00:04:54.890]And on initial project startup,
[00:04:56.600]we'll begin to protect adjacent property
[00:04:58.720]by installing perimeter controls.
[00:05:01.440]These may be maintained for a long time
[00:05:03.620]during construction and ultimately removed
[00:05:05.597]when we have achieved final stabilization.
[00:05:10.600]When considering the timing of things,
[00:05:12.840]the best BMP we have on a site is usually
[00:05:15.730]the existing vegetation.
[00:05:17.840]Try to retain existing vegetation
[00:05:19.700]for as long as possible, especially vegetation
[00:05:22.589]that lies between any disturbed areas
[00:05:24.648]and the right of way or project limits.
[00:05:28.470]Identify where perimeter controls
[00:05:30.170]will be needed as early as possible
[00:05:32.020]and implement them prior to project startup.
[00:05:35.070]NDOT specifications require that perimeter controls
[00:05:38.080]be installed prior to any earth disturbance.
[00:05:41.570]Make sure that these initial perimeter controls
[00:05:43.840]are part of the contractors initial temporary erosion
[00:05:47.510]and sediment control plan.
[00:05:50.470]Identify where runoff from the project
[00:05:52.660]will potentially adversely affect adjacent private property
[00:05:56.320]where you know run off will be anticipated.
[00:05:59.270]Focus efforts where you know water will run
[00:06:02.250]rather than calling for perimeter controls
[00:06:04.230]around the entire site.
[00:06:06.370]Identify critical discharge points
[00:06:08.270]such as adjacent wetlands and drainage ways,
[00:06:11.320]and be sure to consider what type of perimeter controls
[00:06:13.389]will be best suited for the location.
[00:06:18.120]Another useful tool to utilize early on in making decisions
[00:06:21.830]for locating perimeter controls can be reviewing
[00:06:24.740]the permanent erosion and sediment control plan,
[00:06:27.330]using it as a guide for what the designer
[00:06:29.680]may have identified as critical perimeter control points.
[00:06:33.950]Discuss these areas early on during a pre-construction
[00:06:37.020]meeting and plan to include these
[00:06:38.931]as either first installation locations
[00:06:41.661]or as corrective actions in an inspection report
[00:06:45.170]so they're addressed as soon as possible.
[00:06:49.820]So we've noted locations where offsite sedimentation
[00:06:52.960]can or will be prevented.
[00:06:54.920]Installations have been done.
[00:06:56.830]And now we wanna assess the effectiveness of our practices
[00:06:59.861]with the following considerations in mind.
[00:07:02.980]Is the BMP downstream of the areas of disturbance?
[00:07:06.860]Now it seems insulting to emphasize
[00:07:09.100]the common sense fact that yes,
[00:07:10.941]water always runs downhill, but if our practices are not
[00:07:14.820]installed with this in mind, they obviously
[00:07:17.110]won't be effective.
[00:07:19.460]Will the BMP channel a concentrated flow,
[00:07:22.570]potentially creating more problems?
[00:07:25.200]This can happen when perimeter controls aren't installed
[00:07:28.426]on the contour, effectively causing runoff
[00:07:30.020]to run down the hill and potentially undercutting
[00:07:32.990]or bypassing the BMP.
[00:07:36.130]Is there more than 1/2 acre draining to the BMP?
[00:07:40.670]Again, depending on the BMP type,
[00:07:42.672]you don't wanna see it become overwhelmed
[00:07:45.120]because of too much runoff.
[00:07:46.880]It's common to see this happen,
[00:07:48.480]particularly with silt fence.
[00:07:51.350]Is routine BMP maintenance possible in this location?
[00:07:55.540]The BMP may have been installed well,
[00:07:57.730]but during certain phases of construction,
[00:08:00.320]if the BMP can't be properly maintained,
[00:08:03.350]its effectiveness will be minimal.
[00:08:06.020]Have downstream impacts due to BMP failure been considered?
[00:08:10.940]As a SWPPP implementation team
[00:08:12.500]this requires us to have the foresight
[00:08:14.250]to predict what is the worst that could happen
[00:08:17.270]and effectively manage from there.
[00:08:19.760]In this case, if we understand what the significance
[00:08:21.825]of offsite sedimentation could be,
[00:08:24.770]we can begin to make decisions preventing it from happening.
[00:08:29.590]With all these considerations for perimeter controls
[00:08:32.130]in mind, let's look at different BMP types
[00:08:34.660]we may choose for installation on our project
[00:08:37.130]and assess their effectiveness as part of an inspection.
[00:08:40.660]The first BMP type is likely the most common
[00:08:42.762]perimeter control, silt fence.
[00:08:46.790]Some common installation features are also
[00:08:49.340]what you would look for as an inspector,
[00:08:51.470]making sure that the fence is capturing smaller areas
[00:08:54.470]of disturbance often accomplished
[00:08:56.570]by utilizing silt fence bays or J-Hooks.
[00:09:00.640]Most importantly, we wanna avoid concentrating flows
[00:09:03.671]by making sure our perimeter controls are on the contour,
[00:09:07.100]if possible, utilizing these J-Hooks
[00:09:10.000]to slow flows down and not overwhelm our perimeter control.
[00:09:16.410]Here's a scenario where perimeter silt fence
[00:09:18.730]has been installed against the contour
[00:09:21.200]or running directly up the grade.
[00:09:24.200]Again, water runs downhill and always
[00:09:26.880]takes the path of least resistance.
[00:09:29.090]In this scenario, the silt fence has concentrating flows,
[00:09:31.431]allowing a large amount of runoff to run unimpeded to the
[00:09:35.780]bottom of the hill.
[00:09:38.860]Standing in the same place but simply turning around,
[00:09:42.240]you can see what happened.
[00:09:44.050]This perimeter control was installed
[00:09:45.820]with the goal to protect this adjacent wetland area,
[00:09:49.160]but because of the large concentrated flows
[00:09:51.850]and not capturing smaller areas,
[00:09:54.360]the silt fence was undercut and the entire run off fence
[00:09:57.430]was ineffective at this point.
[00:09:59.870]This is a corrective action to document,
[00:10:02.770]but simply repairing the fence and leaving it as is,
[00:10:05.801]would not be the proper solution.
[00:10:08.820]Utilizing silt fence bays to break up these concentrated
[00:10:12.280]flows would work effectively.
[00:10:15.960]When inspecting silt fence ensure
[00:10:17.940]that proper post spacing is installed.
[00:10:21.090]NDOT specifications require six foot post spacing.
[00:10:25.160]Also look for tearing of fabric along the post attachments.
[00:10:28.970]This is a common area for fabric degradation over time,
[00:10:32.470]especially if exposed to windy conditions.
[00:10:35.890]Look for evidence of undercutting or piping
[00:10:38.160]underneath the fence.
[00:10:39.874]Repair any damaged areas and re-compact areas
[00:10:42.303]of undercutting.
[00:10:44.670]If the problem seem to be ongoing,
[00:10:46.310]it may be necessary to either remove
[00:10:48.063]and replace the fence or seek out other BMP alternatives.
[00:10:54.630]Another corrective action to document
[00:10:56.360]during an inspection of a silt fence installation
[00:10:59.010]is clean out.
[00:11:00.990]This goes for any sediment control device.
[00:11:03.610]Be sure to remove sediment once storage capacity
[00:11:06.252]has reached 50%.
[00:11:11.310]Another possible option is to utilize
[00:11:13.330]a mulch perimeter control.
[00:11:15.820]Slash mulch can be specified into a project
[00:11:19.110]during the design process if there is clearing
[00:11:21.540]and grubbing of trees required within the limits
[00:11:23.810]of construction.
[00:11:25.460]The grinding of this tree mass can be utilized
[00:11:27.720]as mulch perimeter control.
[00:11:30.240]The pay items for mulch perimeter control
[00:11:32.510]are by the cubic yard for both grinding and placement.
[00:11:37.570]Here's an excellent example of utilizing
[00:11:39.630]a mulch perimeter control next to a stream.
[00:11:42.770]The location didn't lend itself to other types of barriers,
[00:11:45.520]such as a silt fence.
[00:11:47.450]Slash mulch can be placed anywhere silt fence
[00:11:49.760]or silt checks are indicated in the plan.
[00:11:52.470]The height should not exceed 24 inches.
[00:11:55.580]At the end of its life it can stay in place
[00:11:57.670]or be spread out over the slope
[00:11:59.700]to aid in further sediment control.
[00:12:04.360]In wet or boggy areas mulch perimeter controls
[00:12:07.650]can be a more practical installation than other BMP's,
[00:12:10.580]such as silt fence.
[00:12:12.580]If it poses no adverse impacts
[00:12:14.630]it could be left in place slowly degrading over time,
[00:12:17.800]well after its needed use.
[00:12:21.950]Now let's assess how we need to address stabilizing
[00:12:24.708]inactive areas.
[00:12:26.760]This may include practices such as cover crop seeding,
[00:12:29.660]mulch and hydromulch or tackifiers.
[00:12:35.020]The construction stormwater general permit states
[00:12:37.215]that stabilization measures must be initiated
[00:12:40.930]as soon as practicable, but no later
[00:12:43.523]than 14 days in portions of the construction site
[00:12:47.300]that have temporarily or permanently ceased,
[00:12:50.780]with a few certain exceptions.
[00:12:53.410]Also, installation of stabilization measures
[00:12:55.796]must be completed within 14 days.
[00:13:01.250]Universal rules of thumb for stabilizing inactive areas,
[00:13:04.722]as well as if we're establishing temporary
[00:13:06.946]or permanent vegetation would be the following,
[00:13:09.845]retain existing vegetation as long as possible.
[00:13:13.650]It's the most effective erosion control we have.
[00:13:16.680]Establish new vegetation as quickly as possible.
[00:13:20.770]And as always minimize the amount of time soil
[00:13:23.084]is exposed on a construction site.
[00:13:27.700]Stabilizing inactive areas prior to final stabilization
[00:13:31.160]or implementing permanent erosion
[00:13:32.860]and sediment controls is an important step
[00:13:35.123]during construction projects.
[00:13:37.620]It can be difficult to anticipate where
[00:13:40.070]and when certain areas of a project
[00:13:42.030]are going to sit idle for an extended period of time.
[00:13:45.320]If it's known an area will stay without activity
[00:13:47.415]for more than two weeks, stabilization measures
[00:13:50.356]should commence as soon as possible.
[00:13:53.940]The practices of stabilizing exposed soils
[00:13:56.590]limits erosion potential to both water and wind.
[00:14:00.300]To make the determination how an area is temporarily
[00:14:02.775]stabilized and with what materials,
[00:14:05.655]you'll need to know how long the area will stay inactive.
[00:14:09.650]Will it be less than two weeks?
[00:14:11.940]One to three months?
[00:14:13.610]Less than one growing season?
[00:14:16.010]Perhaps more than one growing season?
[00:14:18.250]And finally, if this inactivity happens towards
[00:14:21.260]the end of the construction phase,
[00:14:22.796]is the site ready for permanent erosion
[00:14:25.810]and sediment control plan installation?
[00:14:30.890]Plan on implementing temporary stabilization
[00:14:33.196]as phases of the construction project pause or finish,
[00:14:37.120]or if it's been determined that final stabilization
[00:14:39.624]will not be initiated yet.
[00:14:42.130]Practices such as cover crop seeding,
[00:14:44.135]straw or hay mulch, hydromulch, soil retention blankets,
[00:14:49.130]or tackifiers are all considerations
[00:14:52.230]given the project areas conditions.
[00:14:54.930]Also, be sure to stabilize any soil stockpiles.
[00:14:58.680]They will be known to stay in place
[00:15:00.520]for longer than a couple of weeks.
[00:15:04.650]Cover crop seeding is a type that is done
[00:15:06.940]for temporary erosion and sediment control
[00:15:09.270]while the project is still ongoing.
[00:15:12.340]Cover crop seeding is done in phase construction areas,
[00:15:14.960]surcharge areas, other disturbed areas
[00:15:17.740]that have not been permanently seeded
[00:15:19.316]or as directed by the project manager.
[00:15:23.040]For cover crop seeding, the goal is to sow seed
[00:15:26.090]that has a good chance of establishing quickly,
[00:15:28.350]such as oats or annual rye.
[00:15:31.170]The cover crop seed selected is typically
[00:15:33.180]a rapidly germinating variety, used for short spurts
[00:15:36.510]where vegetation is needed but not for
[00:15:38.820]an extended period of time.
[00:15:41.430]For finished grades cover crop seeding
[00:15:43.450]needs to be completed within seven days.
[00:15:46.830]Is placement of cover crop seed alone
[00:15:49.084]considered stabilization?
[00:15:51.215]No.
[00:15:52.610]However, once it is germinated and established
[00:15:56.050]cover crop seeding provides the same short term effect
[00:15:58.750]as permanent stabilization.
[00:16:03.120]For rapid temporary stabilization
[00:16:05.345]straw or hay mulch may be applied.
[00:16:08.800]We've covered the installation specifications
[00:16:10.920]for mulch in NDOT's installer certification course.
[00:16:15.340]When considering applying mulch in conjunction
[00:16:17.640]with cover crop seeding remember,
[00:16:19.055]when soil and weather conditions exist
[00:16:22.570]that it's anticipated that the cover crop seed
[00:16:24.890]will not germinate within 10 calendar days,
[00:16:28.310]the project manager or construction engineer
[00:16:30.380]will direct that temporary mulch be applied.
[00:16:36.500]When inspecting mulched areas,
[00:16:38.650]you wanna look for even distribution
[00:16:40.660]of the material over the entire area,
[00:16:43.320]and that the material has been crimped in place.
[00:16:46.480]Here we can see the mulch in the foreground
[00:16:48.730]has good coverage and has been properly crimped into place.
[00:16:53.350]As we look further out into the coverage area
[00:16:55.520]we see that we don't have even distribution
[00:16:58.265]with poor mulch application at the top of the example.
[00:17:02.780]For inspection purposes you want to note this
[00:17:05.780]as a corrective action, as the BMP
[00:17:08.450]has not been installed to specification.
[00:17:13.770]Some things to consider when you are inspecting
[00:17:16.180]a straw mulch application; is there uniform straw coverage
[00:17:20.190]with at least 80% coverage density across the soil surface?
[00:17:24.270]In this example, the mulch density is not consistent.
[00:17:27.840]If this is a temporary application prior
[00:17:29.920]to permanent stabilization installation,
[00:17:32.780]then some reapplication is needed.
[00:17:35.960]Is the material crimped into the soil?
[00:17:39.040]Do you see any erosion occurring in the mulched areas?
[00:17:43.180]Is there a need for additional mulch?
[00:17:46.340]And is there the need for additional BMPs
[00:17:48.950]for better erosion protection?
[00:17:52.940]Another specification for NDOT is temporary seeding,
[00:17:57.240]with a seed mix incorporated into a hydromulch slurry.
[00:18:01.550]Not to be confused with cover crop seeding,
[00:18:03.810]a temporary seating application can be used on embankments
[00:18:06.990]or cuts that are temporary in nature.
[00:18:08.847]Also for stabilization of soil stockpiles
[00:18:12.540]and other areas that require soil stabilization.
[00:18:16.260]When inspecting stockpiles always note
[00:18:18.490]when it is agreed the stockpiles
[00:18:20.380]will remain in place for an extended period of time
[00:18:24.060]and note the need for temporary seeding.
[00:18:27.450]Also for inspection, make sure the proper hydromulch
[00:18:30.450]application rate is being followed
[00:18:32.760]with uniform coverage over the entire stockpile area.
[00:18:36.750]If necessary additional perimeter controls
[00:18:39.680]may be needed as well.
[00:18:41.810]If temporary seeding has failed to sprout,
[00:18:44.476]develop a root system and produce vigorous growth,
[00:18:48.446]reseeding shall be required and shall be performed
[00:18:52.110]at the contractor's expense.
[00:18:56.390]Tackifiers may be an option for temporary stabilization
[00:18:59.620]of inactive areas as well.
[00:19:01.890]This type of BMP is specified by NDOT
[00:19:04.570]as a hydromulch type HM1.
[00:19:08.480]These applications are useful for stabilizing exposed areas
[00:19:11.590]where work will be commencing again soon enough
[00:19:13.806]that may not be suitable for a seeding application,
[00:19:17.400]but still needs treatment for slowing erosion potential.
[00:19:21.030]For inspections make sure areas where tackifiers
[00:19:23.583]have been applied are secure from any foot
[00:19:26.090]or vehicle traffic.
[00:19:28.490]Tackifiers can also be applied over the top
[00:19:30.570]of a mulch application for securing the mulch to the soil,
[00:19:33.996]adhering mulch fibers to one another to provide stability.
[00:19:40.670]Now let's cover stabilizing inactive slopes.
[00:19:44.560]Just like flatter, broader inactive areas,
[00:19:47.690]inactive slopes follow the same rules
[00:19:49.980]for temporary stabilization during a project,
[00:19:52.870]but some additional thought needs to be given
[00:19:54.850]to what BMP to use and how it is performing
[00:19:57.685]once it's installed.
[00:20:01.490]As we've mentioned before, being able to identify
[00:20:04.100]potential slopes for action early in the project
[00:20:07.000]is a great planning tool.
[00:20:08.940]If you're not familiar with the project area
[00:20:10.930]prior to initial construction commencement,
[00:20:13.425]you can review the permanent erosion
[00:20:15.670]and sediment control plans to see
[00:20:17.830]what the SWPPP designer was seeing.
[00:20:19.700]Foreslopes and backslope within the project
[00:20:22.680]should have some controls designed in.
[00:20:25.380]Use these as guidance for what you may encounter
[00:20:28.370]during construction.
[00:20:30.440]How long will the slope stay inactive?
[00:20:33.040]Will it be less than two weeks?
[00:20:35.600]One to three months?
[00:20:37.330]Less than one growing season?
[00:20:39.700]More than one growing season?
[00:20:41.830]This all factors into the appropriate BMP
[00:20:44.530]to select for temporary erosion control.
[00:20:47.770]Are we ready for permanent erosion
[00:20:49.750]and sediment control plan installation?
[00:20:52.280]If so, implement the plan as designed.
[00:20:58.300]If a slope will stay inactive for a short period of time,
[00:21:01.653]and if you have the right equipment available on the site,
[00:21:04.820]vertical slope tracking is a great option.
[00:21:07.860]It's ideal for slope work that still may be in progress.
[00:21:11.730]If weather is in the forecast,
[00:21:13.160]vertical slope tracking alone can cut erosion potential
[00:21:16.460]by as much as 50% over doing nothing.
[00:21:20.140]The pay item is by the square yard.
[00:21:24.350]For slopes adjacent to sensitive areas,
[00:21:26.780]a practice like slope tracking will need to be done
[00:21:29.590]with toe of slope sediment control practices considered
[00:21:33.160]for areas adjacent to streams, wetlands and rivers,
[00:21:36.540]providing a combination of both erosion control
[00:21:39.280]and sediment control BMPs.
[00:21:43.150]Also for slopes less than 3:1
[00:21:46.310]that will be inactive for one to three months,
[00:21:49.620]one possible practice could be mulching.
[00:21:52.740]This can be used in conjunction with cover crop seeding.
[00:21:56.190]This application is best suited for slopes less than 3:1.
[00:22:00.650]As discussed previously, if mulch is selected
[00:22:03.260]for a slope application inspect for any rills
[00:22:06.440]or signs of erosion and consider other practices
[00:22:09.120]if need be for corrective actions.
[00:22:12.410]Consider applying a tackifier rather than crimping
[00:22:15.210]the mulch as this may be more effective
[00:22:17.560]in holding the material in place on the slope,
[00:22:19.960]as well as a potentially easier installation step
[00:22:23.010]than crimping.
[00:22:26.130]For temporary stabilization of 3:1 slopes,
[00:22:29.110]hydromulch used in conjunction with temporary seeding
[00:22:32.380]should be considered.
[00:22:34.290]This is an ideal practice for slope staying inactive
[00:22:37.220]for longer than three months.
[00:22:39.180]Hydromulch is also a practice utilized
[00:22:41.330]for permanent erosion control as well.
[00:22:43.881]For 3:1 slopes, the correct NDOT specification to use
[00:22:48.550]is HM3, bonded fiber matrix.
[00:22:53.901]Inspecting this hydromulch application
[00:22:56.660]on a long foreslope along a highway construction project,
[00:23:00.340]we note that the installation must have been done
[00:23:03.100]from the roadway shoulder sprayed down the slope.
[00:23:06.920]This is typical for a hydromulch application
[00:23:09.600]with the installer using the turret
[00:23:11.900]on the back of the truck, not the hose apparatus.
[00:23:16.120]Because of this, the slope may look like it has good,
[00:23:18.550]even coverage looking down from the top.
[00:23:21.609]But on closer inspection further down the slope,
[00:23:26.181]we see that hydromulch coverage is not 100%
[00:23:30.020]and it's very thin at the bottom of the slope.
[00:23:33.000]To meet NDOT specifications, coverage must be uniform
[00:23:37.112]for the entire slope application.
[00:23:39.920]For installers, this can be accomplished more easily
[00:23:42.082]if the application can be applied shooting
[00:23:45.270]from two directions whenever possible.
[00:23:48.710]If this slope started to erode,
[00:23:50.810]it would run directly into an area considered waters
[00:23:53.490]of the state, a violation of our permitting.
[00:23:56.960]To correctly identify this corrective action in the field
[00:24:00.540]it's critical that an inspector
[00:24:02.540]can see all areas of the project.
[00:24:05.940]If the SWPPP management team feels
[00:24:07.670]that this is an inadequate BMP for the scenario,
[00:24:11.030]another practice must be selected and installed.
[00:24:16.300]For stabilized slopes that need protection
[00:24:18.450]from runoff coming from the top of the slope,
[00:24:21.150]typically from a roadway or bridge deck,
[00:24:23.370]still undergoing construction,
[00:24:25.350]a temporary slope drain can convey stormwater
[00:24:28.240]to the bottom of the slope, preventing rills
[00:24:30.710]and gullies from forming.
[00:24:32.820]It's a flexible pipe extending the length
[00:24:35.120]of a disturbed slope to divert stormwater.
[00:24:38.370]The size of the pipe should be selected
[00:24:40.090]according to the amount of drainage area.
[00:24:44.600]Temporary slope drains can work well
[00:24:46.470]in areas with lots of drainage
[00:24:48.510]and where vegetation has not established yet,
[00:24:50.550]or final hydraulic structures are not yet installed.
[00:24:55.240]For inspection, you wanna make sure stormwater
[00:24:57.810]is channeled into the inlet.
[00:24:59.950]If there is a point near the inlet
[00:25:01.980]where water can bypass the inlet
[00:25:04.290]you can be sure it will begin to erode around it.
[00:25:08.130]Reinforce this area with sandbags,
[00:25:10.020]providing a sturdy structure to prevent storm water
[00:25:12.530]from bypassing the inlet.
[00:25:14.730]At the bottom of the drain, make sure there is adequate
[00:25:17.051]scour protection and that there's an area
[00:25:19.970]for sedimentation to occur before
[00:25:21.770]it leaves the right of way.
[00:25:24.900]Once the project gets to the point
[00:25:26.580]where you can initiate your permanent erosion
[00:25:28.850]and sediment control plan, you may have soil retention
[00:25:32.010]blankets installed on foreslopes and backslopes.
[00:25:35.410]These BMPs are effective for stabilizing slopes
[00:25:38.240]for more than one growing season
[00:25:39.981]and makes it ideal for protecting slopes from erosion.
[00:25:42.980]while permanent seeding can become established.
[00:25:48.060]When inspecting soil retention blankets,
[00:25:50.170]you want to ensure that good mat to soil contact
[00:25:53.120]is consistent throughout.
[00:25:55.200]This is accomplished during the installation process
[00:25:57.350]by proper seedbed preparation.
[00:25:59.871]It's critical to make sure the most of the humps
[00:26:02.140]and bumps of a treatment area are smoothed out,
[00:26:04.820]allowing for good seed germination conditions,
[00:26:06.992]as well as good mat to soil contact.
[00:26:10.480]In this example, you can see evidence
[00:26:12.450]that the blanket has been installed over existing
[00:26:15.080]soil clods, leaving void spaces underneath
[00:26:18.112]where runoff can collect and begin to form rills
[00:26:20.940]and gullies underneath the blanket.
[00:26:24.616]When inspecting blankets for proper installation,
[00:26:27.970]look for proper staple placement.
[00:26:30.560]With each blanket type, a specific staple pattern
[00:26:33.650]is specified.
[00:26:35.300]Lift on the blanket to check if staples
[00:26:36.941]were installed correctly.
[00:26:38.960]In this example, the inspector should not be able
[00:26:41.650]to lift the blanket this high.
[00:26:44.090]This is evidence that not enough staples
[00:26:45.611]were used during the installation.
[00:26:48.360]This can lead to poor blanket performance
[00:26:50.221]and the potential for erosion.
[00:26:53.620]If installed in a ditch application,
[00:26:56.050]verify if staple check slots have been installed
[00:26:59.220]every 25 to 30 feet, forming a continuous row
[00:27:02.900]of staples across the width of the ditch area.
[00:27:06.670]Also check if blanket edges have been properly stapled
[00:27:10.300]and are secure.
[00:27:11.630]And finally verify the proper staple size
[00:27:15.280]was used and is to NDOT specifications.
[00:27:20.690]For permanent erosion and sediment control inspections
[00:27:23.270]you may also see a combination of soil retention blankets
[00:27:26.900]and silt checks used.
[00:27:29.670]Silt check Type 1-High is commonly designed
[00:27:33.210]and installed for use as a slope interruption,
[00:27:36.120]aiding an erosion prevention down the slope.
[00:27:39.680]For inspections check for proper staking of the check.
[00:27:43.490]In this example, staking looks to be too far apart.
[00:27:47.350]NDOT special plans call for staking
[00:27:50.330]no more than two feet apart.
[00:27:53.780]Also look for evidence of rilling
[00:27:55.750]or undercutting along all of the silt checks
[00:27:58.437]and document as a corrective action for needed repairs.
[00:28:05.410]Let's continue our walkthrough of the construction site
[00:28:08.270]focusing now on stabilizing ditches.
[00:28:13.590]Like all other areas we've seen so far
[00:28:15.900]for considerations of proper stabilization,
[00:28:18.900]the type of practice to utilize depends on how long
[00:28:21.690]the area will stay inactive.
[00:28:24.060]Is it less than two weeks?
[00:28:26.030]More than two weeks?
[00:28:27.580]One to three months?
[00:28:29.230]Or is this ditch area ready for a longterm solution
[00:28:32.950]such as implementing the permanent erosion
[00:28:35.270]and sediment control plan?
[00:28:39.090]If the ditch area will be inactive only a short time,
[00:28:42.660]it'll still be an active conduit
[00:28:44.610]for stormwater runoff during and after a rain event
[00:28:47.910]and the installation of earth checks
[00:28:50.080]with a silt trap would be a good BMP combination
[00:28:53.490]in this scenario.
[00:28:55.110]These are short term BMPs that can be built
[00:28:57.580]with the right equipment onsite.
[00:29:00.160]For inspections and documenting corrective actions,
[00:29:03.600]look for erosion occurring through or around the check.
[00:29:08.080]If the checks are going to continue to be used,
[00:29:10.550]note corrective actions for necessary repairs.
[00:29:14.100]Also, ensure a proper spacing between the checks.
[00:29:18.050]Is there gully erosion forming in between the checks?
[00:29:21.640]This is an indication that the spacing of the checks
[00:29:24.500]may be too far apart and additional checks may be needed.
[00:29:29.480]Remove sediment from the silt trap in
[00:29:30.431]front of the check.
[00:29:32.530]when it reaches 1/2 of its capacity.
[00:29:35.670]Temporary stabilization of foreslopes and backslopes
[00:29:38.980]contributing flows to these checks
[00:29:41.350]should be done as soon as possible
[00:29:43.320]and inspected for effectiveness.
[00:29:47.240]Another short term BMP consideration
[00:29:49.770]for stabilizing ditches could be installing
[00:29:52.580]high-porosity silt fence.
[00:29:55.360]While high-porosity silt fence does provide
[00:29:57.940]some sediment retention it mainly provides
[00:30:00.840]energy dissipation, slowing flows within the ditch.
[00:30:05.160]It's typically installed with a silt trap
[00:30:07.280]immediately on the upstream side.
[00:30:09.850]As with all silt checks, spacing is key.
[00:30:13.200]Make sure there are enough checks in the ditch line
[00:30:15.193]to be effective in slowing flows and capturing sediment.
[00:30:21.840]For most temporary erosion and sediment control
[00:30:24.440]considerations for silt checks,
[00:30:26.560]selection will come down to the amount of flows
[00:30:28.960]the ditch will receive.
[00:30:30.810]For smaller drainage areas and ditches with less slope
[00:30:33.910]in urban settings type 1-High checks
[00:30:37.730]is a reasonable selection.
[00:30:39.710]For larger contributing drainage areas
[00:30:41.870]and ditches was steeper slopes, type 2-High silt checks
[00:30:46.025]may be appropriate.
[00:30:48.560]As always if in the course of an inspection,
[00:30:50.870]it is clear the BMP selected is not working,
[00:30:54.680]another practice must be selected
[00:30:56.850]and installed as part of a corrective action.
[00:31:00.390]Let's discuss these two main types of silt checks
[00:31:03.010]for temporary ditch stabilization.
[00:31:06.530]Silt check type 1 is a straw wattle,
[00:31:09.540]a more and more common BMP on construction projects.
[00:31:13.137]With proper selection, placement and installation
[00:31:16.450]it can be an effective BMP for slowing erosive flows
[00:31:20.260]in a ditch, as well as provide some sediment capture.
[00:31:24.760]NDOTs special plans for these types of silt check
[00:31:27.680]show various scenarios where they can
[00:31:29.630]be installed correctly.
[00:31:31.580]For inspection purposes, make sure flows
[00:31:34.560]coming at the check, have no choice
[00:31:37.170]but to flow over the check in the middle
[00:31:39.610]of the ditch cross section.
[00:31:41.970]Flows will flow around the check
[00:31:43.860]if the ends of the check are not installed higher
[00:31:46.223]than the middle of the check and we'll form gullies.
[00:31:50.320]Also, make sure proper posts and post spacing has been done.
[00:31:55.210]Post spacing should be no greater than two feet apart.
[00:32:01.820]The other common type of wattle silt check
[00:32:03.930]is a type 2 or wood fiber wattle.
[00:32:07.770]These are used in urban and rural ditches
[00:32:09.920]where slightly higher flows are anticipated.
[00:32:13.250]Again, many of the installation specifications
[00:32:15.940]are the same as type 1 straw wattles.
[00:32:19.170]If installing these as a temporary BMP,
[00:32:22.023]it's good to reference the permanent erosion
[00:32:24.600]and sediment control plan as a guide,
[00:32:27.130]if silt checks have been designed into the permanent plan.
[00:32:30.240]Use this as a guide for proper placement
[00:32:32.970]and spacing, as this is critical to the BMP's effectiveness.
[00:32:38.880]If is available for the creation of slash mulch
[00:32:41.606]from clearing and grubbing of tree mass,
[00:32:44.530]it can also be used as a silt check
[00:32:46.500]in a ditch application whenever a silt check is specified.
[00:32:51.030]Follow the special plans for proper installation
[00:32:53.660]of these slash mulch silt checks,
[00:32:56.110]ensuring that the checks are lower
[00:32:58.170]than the adjacent roadway as to not potentially
[00:33:01.080]pond water on the road.
[00:33:03.710]Also, we wanna ensure that water has no choice,
[00:33:07.270]but to flow over the center of the check.
[00:33:10.210]Inspect to make sure the ends of the check
[00:33:12.290]are higher than the middle.
[00:33:14.270]The check height should never exceed 24 inches.
[00:33:19.240]The permanent erosion and sediment control plan
[00:33:21.320]may specify the installation of rock checks.
[00:33:24.970]For inspection purposes, make sure the correct rock size
[00:33:28.190]was used in the installation per the plan set.
[00:33:31.760]Also, make sure storm water flows are going through
[00:33:34.890]and over the rock check and not around.
[00:33:38.330]This is an indication that the check
[00:33:39.850]was not installed correctly.
[00:33:41.820]If flows are bypassing around the check
[00:33:44.130]and causing erosion, this is a corrective action
[00:33:46.490]to document and a BMP to repair or re-install.

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NDOT Erosion Sediment Control Inspector Re-Certification Section 3 Part 1

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