Sheetflow Construction Erosion and Sediment Control

November 12, 2019

Hydroseeding on Blanket Instead of Under Not the Best

Filed under: Video — Tags: , , , , , , , , — Sheetflow @ 7:18 am

This is not the best way to get grass growing. The seed sits on the blanket which is a quarter to half inch above the soil. Since the seed needs to be in contact with the soil to have the best chance of growing, this will reduce the quantity of grass that grows. In a ditch, the more grass the better. The best way is to hydroseed first and then install the blanket.

November 5, 2019

Inspecting Sand Bag Check Dams

How to inspect sand bag check dams.

October 22, 2019

You Don’t Always Need to use Silt Fence

September 17, 2019

Can’t Get Away From It

It doesn’t matter where I go, I always see some type of construction erosion issue. I went to visit relatives in Portland, Maine, flying in and out of Boston Logan International. In the terminal, waiting for my flight back home, I saw a construction project on the ramp; it had rained a few says before, hard. Obviously, the stockpile had not been covered before the storm and sediment washed off the pile into the drain.

I work at an airport that operates under strict turbidity effluent limits; here is how we do this kind of work:

(1) rarely do we allow stockpiles on the ramp because we rarely reuse the excavated material (it is either contaminated, unsuitable or doesn’t meet current FAA requirements); it is direct loaded into trucks and hauled off. When we do stockpile, we place dirt on plastic and cover it with plastic, using lots of sand bags to secure it from jet blast and wind.

(2) work areas are always isolated so there is no runoff from the site. Normally, we use four-inch extruded asphalt curbing along the base of the jersey barriers. Rolled hot mix asphalt (HMA) is used at the entrance point so water is contained but vehicles can access the site.  Water that builds up inside the curbing is pumped back into the excavation if clean, or a tank if contaminated.

I should have mentioned that we also have strict sediment trackout requirements: no visible sediment leaves the site at any time.  This is both because of the effluent limits and for safety reasons; dirt and debris that gets sucked up into a jet engine is damaging and possibly deadly.

Lastly, I am not casting aspersions on the folks at Logan; I don’t know their situation, permits, drainage system, or tolerance for risk.  Because of my situation, I have low risk tolerance for potential non-compliance with our permit and I notice when something would cause me grief at my airport.

September 10, 2019

Preparing for Fall and Winter Rains

It’s that time again…..

Winter is approaching, now is the time to get construction projects ready. Here are some things to consider:

Cover bare soil. Final grades can be covered with hydroseed, erosion blankets, topsoil, bark or whatever final cover is planned for the project.

Get your hydroseed contractor lined up now and avoid the October rush.

Don’t open up more than a few acres after September 1st.

Grades that aren’t being actively worked can be covered with straw at a rate of 1500 pounds per acre. This is a very cheap and effective way to protect bare soil from raindrop impacts and erosion. Hand seed before spreading the straw. Spray it with water to help hold it in place.

Track your slopes with a Cat: up and down slope, not across slope. The first helps prevent erosion, the second speeds it up.

Use flex pipe drains at bridge ends if your permanent drainage system and curbs are not in place. Collect the water from the bridge using sand bags and divert it to the pipe. Make sure the pipe is long enough to reach the bottom of the slope.

Use a water truck and water seeded areas weekly to get quicker growth. The better the growth going into winter the better.

If you have to open up a large area, only clear and grub small areas. You can clear larger areas if you don’t grub. Roots and slash help protect the bare soil.

Walk the site looking only at erosion controls, thinking ahead of areas that could have a problem. Identify them and start making additions and corrections.

Locate all existing water flows in and around your project and find out where they drain to.

Think about maintenance and regular inspection of erosion controls. When are silt fences going to be inspected and who does it? Who removes mud from check dams? Who covers slopes with straw or other mulch?

Get materials on site now. Again beat the rush for materials in October and November when everyone is in a panic to get plastic and straw. Stockpile enough straw, plastic, silt fence, flex pipe, sand bags, seed, rock, now to cover all areas that are bare.

Set up emergency procedures now. Who should be called in emergencies? Do you have a WSDOT certified Erosion and Spill Control Lead? Brief your personnel on what to do if they see muddy water and who to go to.
Make sure that erosion control material installers know proper installation methods.

Make sure all your silt fence is installed on contour with the ends flared up slope a few feet. If it is not on contour, identify the lowest points of the fence as these will be the failure spots. Install a double row of silt fence at these low spots before you have a failure. Double up your silt fence in areas where eroding slopes could flow into wetlands or streams.

Do you have bare spots where previous seeding hasn’t grown? Cover it with seed and straw if the area is small, remobilize the hydroseeder for larger areas.

Make sure all catch basins within the project boundary are protected with inserts, fence surrounds, or other methods to keep mud out. Locate any catchbasins outside project boundaries that may receive water from your site and protect them.

Make sure that you have a copy of the Stormwater Site Plan (SSP) and Temporary Erosion and Sediment Control plan (TESC) and any grading or environmental permits on site in the job shack. Know what they say. Give each inspector a copy of the SSP and TESC to keep in their truck. These are working copies that can be adapted to site conditions.

Modify your permanent stormwater ponds into temporary sediment ponds by installing a standpipe and blocking the outlet with sand bags. Cut a few small holes in the standpipe to allow for slow release of water. You can also use perforated pipe as the standpipe and hold it in place with “T” posts, wire, and gravel piled up around it.

Use geotextile fabric as a temporary ditch lining to protect bare soil from erosion. Hold the fabric in place with rock check dams, wooden stakes, or sand bags.

Make sure that all check dams are installed so that the top center point is lower than the bottom end points. This prevents endcutting. You may have to add more material to the dam to increase the width, especially on wide ditches with shallow grade side slopes

July 20, 2019

Water-filled Diversion Berm

Photo: David Jenkins

I am always looking for products and materials that achieve the goal of environmentally friendly erosion controls, such as this reusable best management practice.

Specification
Materials

A. Berm shall be a minimum 6 inches high and 10 feet long and made of 10 mil polyurethane or 22 oz. PVC.

Construction Requirements
Water Filled Diversion Berms

a. Water filled diversion berms shall be installed such that offsite water is prevented from entering the job site and site water is kept within the project boundary.
b. Berms may be used to prevent contaminants and water from entering catch basins.
c. Berms may be used on impervious surfaces.

Payment
O. Payment for “TESC – Water Filled Diversion Berms” will be made at the contract unit price per each per month as stated in the Schedule of Unit Prices, and shall be full compensation for furnishing the specified diversion berms. The unit price per each shall include the cost of mobilization/demobilization, cleaning, hauling and all incidentals for the number of diversion berms required by the Engineer for the duration of the contract.

July 9, 2019

Managing Construction Stormwater on Concrete Tiltup Building Project

Video: David Jenkins

June 15, 2019

Erosion in Austin

photo:David Jenkins

I did find some erosion in Austin.

June 14, 2019

Horizontal Silt Fence

Photo: David Jenkins

Walking around South Congress district south of downtown Austin, I discovered a new best management practice-horizontal silt fence. This makes access to the work area so much easier than if vertical silt fence was used. Fortunately no rain in the near future.

April 9, 2019

Process Wastewater

What is process wastewater?

The definition of process wastewater and how it applies to construction has always been a bit confusing to me.  There are some construction activities that are obvious generators of process water like pressure washing, but then there seems to be some grey when it comes to filling a water truck from a hydrant and using the water for dust control. 

I suspect regulators, if you ask them, will give some conflicting definitions of construction process water.  I am going to try to work through this over a few days, or weeks or however long it takes to come up with a satisfying answer. 

First off, how do the Feds define it? Process wastewater as defined by 40 Code of Federal Regulations (CFR) 122.2. https://www.law.cornell.edu/cfr/text/40/122.2

 it says: “Process wastewater means any water which, during manufacturing or processing, comes into direct contact with or results from the production or use of any raw material, intermediate product, finished productbyproduct, or waste product.

EPA uses this definition in their NPDES Glossary. Find at https://www.epa.gov/npdes

The Washington State Department of Ecology uses that definition in the Construction Stormwater General permit and adds: “If stormwater commingles with process wastewater, the commingled water is considered process wastewater”.

This is the legal definition of process wastewater.  It is a good, solid, bit of legalese, developed by lawyers for lawyers.   Though I haven’t researched this, I think it is likely this definition originated when the Clean Water Act was in its beginning stage of development and was applied to industrial, “end of pipe” discharge facilities, like chemical plants, and manufacturers. 

Herein, I believe, lies my confusion; construction doesn’t fit this description.  I guess technically it is, or can be, an end of pipe facility, but construction is transient, has a limited duration, and generally has the potential for diffuse discharges rather than just one or two discreet discharge points.

With that, I will think some more and post some more when my headache goes away.

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