Steep slopes on a construction site can lead to some problems when talking about erosion control and water runoff. Slopes greater than 3:1 allow water to quickly run down the slope leading to erosion and possible water damage downhill. In this month’s development digest, we discuss slope surface roughening techniques and why they are a beneficial practice on an exposed slope during construction.

What is slope surface roughening and what is the purpose? Slope surface roughening is the act of roughening up or raking the surface of a slope horizontally to create grooves, bumps, and depressions. These bumps and depressions on the slope serve multiple purposes including:

• Slowing down water velocity flowing down slope
• Trapping sediment that may wash down the slope
• Providing a better base to grow vegetation

Water running down a slope at a high velocity creates the potential for large soil erosion and damage, and by working grooves into the slope, the water is slowed down at every bump it reaches, resulting in a decreased velocity. The same idea is used when talking about trapping sediment. Like flowing water, the grooves and bumps create somewhat of a barrier for sediment moving downhill and some of the sediment gets trapped on the hill, which means the sediment is not flowing into the creeks and streams. Slope roughening is also good for vegetative growth because the depressions create a great place for the vegetation to establish. A flat, compacted slope creates a difficult surface for the vegetation to establish, and by providing depressions and loosening up some of that soil, the vegetation is more likely to survive and provide ground cover. In fact, according to the Ohio Rainwater and Land Development Manual, any slopes that are steeper than 3:1 are required to be grooved or tracked if vegetation will eventually be installed, so you might as well create those grooves before construction starts for soil erosion control as well!
 
Two main methods to roughen the slope are commonly used:

• Dragging a bucket with teeth along the slope
• Driving tracked machinery horizontally across the slope
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Using a bucket with teeth to drag along the slope is a very simple and effective method to create the grooves and depressions needed to slow down the water velocity. Using tracked machinery is also a good method that can lead to uneven grooves along the slope that will also help slow down water velocity. Both methods can be an effective way to roughen up the soil, however the track method may not be as good of an option depending on the soil because it could lead to soil compaction, which would not be good for vegetative growth. It is best to determine the soil type before choosing one of these methods.
 
Slope surface roughening is a tried and proven practice that works effectively to assist in the battle against soil erosion and water runoff. Whether using a bucket with teeth, equipment tracks, or any other method that roughens the slope, the creation of the grooves and depressions is a great practice to protect the soil and the water during the construction phase of a project. More information and specifications can be found in the Ohio Rainwater and Land Development Manual which is linked below.
 
Have questions about this practice, other best management practices, or other questions in general? Feel free to reach out to our office by calling us at (513) 695-1337 or emailing at [email protected].
 
Ohio Rainwater and Land Development Manual: https://epa.ohio.gov/wps/portal/gov/epa/divisions-and-offices/surface-water/guides-manuals/rainwater-and-land-development
 
Article Written by Seth Byerly, Urban/Ag Technician

"April showers bring May flowers". Those same rain showers can contribute to other types of blooms; algal blooms. Plants need sunlight, nutrients, water and a favorable environment in which to grow. Algae have similar requirements. A shallow basin allows intense sunlight to shine to the bottom and allows the water to heat up quickly. Longer spring days mean more sunlight available to the algae. Warming temperatures also contribute to the growth of the algae. Nutrients that are bound to sediments can wash into the basin from the surrounding drainage area and help drive algal blooms.
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Why does algae in a basin matter? Algae is a part of any heathy aquatic ecosystem so at normal levels they are not a problem. When one species of algae blooms, it can lead to maintenance issues and other problems. Let’s look at algae blooms and their impact on the function of the stormwater basin. Dense algal scums interfere and obstruct parts of the basin’s outlet structure, causing it to lose storage capacity or overfill. Algae that die off will sink to the bottom, decay and will eventually fill the basin with muck. This can lead to costly maintenance. 

Beyond the maintenance implications of an algae bloom, there are health and aesthetic implications. As an algal bloom dies off and decays dissolved oxygen in the water is depleted. This can lead to a fish kill. While not all algae blooms would cause a health impact, there is one class of “algae”, the cyanobacteria, that can release harmful toxins when they bloom. The toxins they release can harm pets that wade or drink the water. There can also be respiratory impacts from severe blooms.  Water quality also includes aesthetics. A homeowner who just paid $500K to move into a nice community is less likely to appreciate a basin with a thick algal scum. This can hurt real estate values in the area.

The best way to reduce the impact of a harmful algae bloom is to work to prevent blooms. This starts in the design phase. Designing a wet extended retention basin to a depth of 6-8 feet and with sufficient bank grading will reduce plant growth and algae blooms in the basin. A dry basin should be constructed so it doesn’t hold water for more than 72 hours. During the construction phase, limit the amount of sediment that flows into the basin. This sediment will have bound up nutrients and will provide the food leading to future algae blooms. Remove built up sediment in the basin, the presence of a forebay should make this maintenance easier. Stabilize the basin walls and surrounding ground with seed and straw to help lock soil and nutrients in place, keeping them out of the basin.
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Post-construction measures like keeping a vegetated buffer around the basin will help keep the sides of the basin from caving in. The taller vegetation will also discourage geese from hanging out around the pond and adding more nutrients. The vegetation buffer will act as a filter strip. Native sedges, blue flag iris and rushes are a few plants recommended as native buffers. Woody vegetation and nuisance vegetation should be discouraged. Keep grass clippings out of the basin. Bottom-up aeration can help support a healthy ecosystem and help regulate temperature. Also encourage residents to be responsible if they are applying fertilizer to their lawns. Adopting the four Rs of nutrient management for your lawn can be useful.

​Considering that fertilizer will lead to more costs, mowing, and maintenance, some may decide to forego it.  With proper design and maintenance, the stormwater basin will remain functional and be more enjoyable to have in the community.

​For more information, contact our office at 513.695.1337

​Sediment and erosion control is always a challenge on construction sites when soil is exposed to the wind and rain. As rain falls on the exposed soil, it loosens it up and begins to wash away as fine-grained sediment. Sediment is the top pollutant impacting Ohio’s streams. It clouds the water column, choking out aquatic life, and changes stream morphology by settling out in areas of slow flow. Alluvial fans are a great large-scale visualization of this (Fig. 1). As the water slows down, it drops the sediment out which raises the ground level. Water will seek a new path of least resistance. Hopefully not towards someone’s house! Sediment can change stream morphology too. Deep pools within a stream provide cool-water habitat for fish and these can be filled in as sediment is deposited. What once was a great swimming hole is now too shallow. One way we can reduce sediment discharge to Ohio’s lakes and streams is by installing sediment settling basins on construction sites. These are required by the Construction General Permit as the stormwater must be treated before being discharged from the site.

​A sediment basin is a temporary settling pond that filters runoff and releases it at a controlled rate. They can be used for sites where the drainage area is 100 acres or less. Any project that increases the impervious surface is required to have a permanent, post-construction stormwater basin, so it makes sense to install the sediment basin on the low point of a site, where it will be converted to its post-construction design at the end of the project. They should be installed as a first step to the mass grading process, so they can be functional and ready to accept sediment-laden runoff once the earth is disturbed. Since sediment basins trap sediment, the sediment will need to be removed before project completion. This ensures that the basin has the proper water quality storage capacity when it gets converted to the post-construction stormwater design at the end of the project. All these considerations should guide the design process.

​Ohio EPA’s Rainwater and Land Development Manual (https://epa.ohio.gov/divisions-and-offices/surface-water/guides-manuals/rainwater-and-land-development) is the guiding document for stormwater practices used during development. Chapter 6 covers sediment basin design. Figure 3 illustrates the various components of the design criteria, which includes pool design, embankment design, dewatering design, and spillway design. A floating skimmer device (Fig. 4) is required throughout the duration of the project to drain the water from the top of the water column, where the sediment is less concentrated. So, install the skimmer and let it simmer!

The Ohio EPA has created a sediment basin compliance tool, which we require to be completed for all projects. This tool is helpful to determine the sizing of your basin by inputting numbers relating to total disturbed area and total drainage area draining to the basin. The dewatering zone shall be a minimum of 1800 cubic feet per acre of drainage while the sediment storage zone shall be 1000 cubic yards per disturbed acre that drains to the basin. After inputting the drainage area and disturbed drainage area, it will calculate the required sediment and dewatering zone volumes as well as the orifice size and skimmer size. There is also a Water Quality Volume tool very similar to this tool that guides the post-construction stormwater design. Our office is happy to provide these tools to you upon request.
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Stabilization is not just important for upland controls, but the basin itself should be smooth graded and stabilized as a first step to the mass grading process. That way the basin can be in place before any upslope disturbance occurs to accept sediment-laden stormwater. Towards the end of the project, when the entire site is stabilized, the sediment basin needs to be converted to its post-construction stormwater design. This usually entails removing the skimmer device and installing an orifice plate to achieve the proper water quality orifice size for post-construction treatment of stormwater. As-Builts need to be completed and submitted to the Engineer of Record for the municipality.

​Sediment basins should not solely be relied upon as the only sediment and erosion control measures on a site. Ohio EPA has found that they are only about 50-80% effective at removing sediment. The finer silt particles remain suspended in the water column and are too small to filter out. That’s why a whole toolbox of SECM’s should be used on a site.  The best management practice (BMP) is to prevent erosion and sediment transport in the first place by stabilizing areas at final grade or areas that lie dormant for longer than 14 days. Ohio EPA has found that erosion control BMPs like stabilization are 90-98% effective. So, it takes multiple tools to properly handle stormwater runoff on a site. Sediment basins are a crucial part of the stormwater solution by satisfying both water quantity and water quality requirements. And don’t forget, install the skimmer and let it simmer!

For assistance, please call our office at 513.695.1337

​Article Written by Justin Bedocs

Stabilization when a site has completed construction is one of the most important BMPs that we can install to prevent erosion and sediment pollution. Stabilizing exposed sediment covers the ground from stormwater runoff, allows roots to be put into the ground to hold the sediment in place, and in general, stabilization is much more pleasant to look at than just bare dirt. In this month’s Development Digest, we will dive into a few species of grasses that can be used for stabilization, and the circumstances in which each species is recommended. 

Two different types of stabilization need to be considered when choosing grass species. Is the seeding being done temporarily, or will the grass be permanent? According to the Ohio EPA Construction General Permit (CGP), any area that will remain idle for over 14 days but less than one year needs to have temporary stabilization. For example, this means that a site that will be dormant for 9 months should be mulched and have seed put down to protect the exposed sediment. When talking about temporary stabilization, we want to have a grass that is going to pop up quick to provide that protection as soon as possible. A mixture of seed is recommended to get optimal cover. Perennial rye grass is a good species to have in the mix for sites that will be dormant for longer periods of time. Oats are a good species to include, especially during the cooler weather since they are able to grow quickly. In the Ohio Rainwater and Land Development Manual table 7.8.1 there are mixes that are great to use for temporary stabilization. Below are some of the mixes:

• From March 1 to August 15
  • Oats, Tall Fescue, Annual Ryegrass
  • Perennial Ryegrass, Tall Fescue, Annual Ryegrass
  • Annual Ryegrass, Perennial Ryegrass, Creeping Red Fescue, Kentucky Bluegrass
• From August 16th to November 1st
  • Rye, Tall Fescue, Annual Ryegrass
  • Wheat, Tall Fescue, Annual Ryegrass
  • Perennial Rye, Tall Fescue, Annual Ryegrass

For exact seeding rates, please refer to table 7.8.1 on the Ohio Rainwater and Land Development Manual which is linked at the bottom of this article. The big takeaway when choosing a species for temporary stabilization is to find a mix that can survive the cold. Grasses such as the ryes and the fescues are good in the cold season, so they are great options for the temporary seeding.
 
Permeant seeding is to be completed when the construction activity has concluded, at least for a year or more, and so the grass species for permanent seeding can defer from temporary seeding. Per the Ohio CGP, any areas that will be dormant for over a year, or that have reached final grade, should be permanently stabilized. So, what are some of the species that can be used for this practice? Erosion from water runoff is a big issue in Ohio, and so whatever seed mixes that we choose, it should be a nice dense grass that will also promote infiltration into the ground. Table 7.10.2 of the Ohio Rainwater and Land Development Manual provides a list of mixes that are great for permanent stabilization. If nothing else, tall fescue is always a good option for permeant seed. For general use such as lawns and common areas, good options for seed mixes are as follows:

• Creeping Red Fescue, Domestic Ryegrass, Kentucky Bluegrass
• Tall Fescue
• Turf-type Fescue
• Kentucky Bluegrass with either Perennial Ryegrass or Creeping Red Fescue

The recommendations that the Ohio RLDM gives for steep slopes are very similar, there is a couple different species, however. Tall fescue is generally a very good grass to use on slopes, there are also other options that can be mixed with tall fescue. Below are recommended seed mixes for permanently stabilizing a steep slope, the exact seeding rate can be found on the Ohio RLDM:

• Tall Fescue
• Crown Vetch, Tall Fescue
• Flat Pea, Tall Fescue

Road-side ditches and swales take in a lot of water flow, and so the seed species can also be different for these waterway features. Because these areas can potentially take on a lot of water in a short amount of time, grasses that can handle the high velocities are important to have. Below are a couple of good mixes listed from the Ohio RLDM for this purpose:

• Tall Fescue
• Turf-type (dwarf) Fescue, Kentucky Bluegrass

One of the most effective BMPs that we can use on construction sites to prevent soil erosion and pollution is temporary and permanent stabilization. Putting grass seed down on exposed soil ensures that the soil is covered, and rain and flowing water cannot loosen it and sweep it away. By seeding and stabilizing exposed areas when they plan to be dormant or reach final grade, we can ensure that the soil is not running into waterways and causing further pollution to the waters of the state. Now is a great time to start planning the permanent stabilization process because the seeding window for the year opens on March 1st. Grass is one of our greatest allies in the fight against soil erosion, let’s make sure we utilize this BMP and see some green start to pop up on the exposed soils as we move into the Spring months!
 
For more information on stabilization, or any other construction site BMP, please contact our office at 513.695.1337.
 
Links:
Ohio Rainwater and Land Development Manual
Ohio Construction General Permit

Written by Seth Byerly, Urban/Ag Technician

Stormwater Infrastructure helps to convey rainwater, prevent flooding of homes, roadways, all while protecting water quality. Many factors can impact water quality. In this article we will look at water temperature and how stormwater infrastructure can help maintain healthy streams and lakes.
As areas become more developed there is an increase in impervious surface area. On a sunny day paved surfaces can transfer heat to the air above them and to stormwater as it flows over. The surface temperature of a parking lot can exceed 140°F on a clear summer day. This is almost hot enough to fry an egg. During a rainstorm, pavement also allows water to flow unimpeded into the storm drains. Water flowing off hot pavement becomes warmer and can cause thermal stress to organisms living in the receiving stream.

Fish and macroinvertebrates, tiny organisms which make up the base of the aquatic food chain, have a temperature range that they are well adapted to. Think of trout living in a cool mountain stream. Fish have adapted over many thousands of years to the environments in which they live. Increasing the temperature of a stream over time or subjecting the stream to sudden fluctuations in temperature will stress the fish populations in that stream. Some heat tolerant species will survive while less tolerant species will see a drop in numbers. There are many reasons for this, one of which is dissolved oxygen. Colder water can hold more oxygen which fish breath through their gills. Warmer water holds less oxygen. While our native fish populations do worse with increased stream temperatures, certain algae species can do well in warmer waters. These algae will bloom, creating additional stress on the fish since they can deplete oxygen in the water. To further complicate things, urbanization typically results in less tree canopy around streams resulting in less shade and higher water temperatures.

​Stormwater controls can help to reduce thermal stress on fish and other aquatic organisms. Grassed swales can slow down water and help it to infiltrate. Establishing clearing limits around streams helps to maintain a filter buffer or better yet, a tree canopy around the streams.
How can stormwater infrastructure help to maintain good water quality. One piece of infrastructure that can make a big difference is the basin.

In our example of hot water flowing off a parking lot, the basin slows the flow down giving the water time to cool to safer levels. Once in the basin heat transfer can occur between the water and the basin. Some transfer also takes place between the water and the air. The rate of heat loss is determined by the “specific heat” of water. The specific heat it is the amount of energy needed to change the temperature of water by 1 degree. A significant amount of energy needs removed to reduce the temperature of water. We can’t change the air temperature or how much rainfall is received.  What can be influenced is how long it takes water to flow through the basin. This is done by oversizing the basin and by installing the water quality orifice when converting the outlet structure over to post construction design. A larger basin will have more storage, increasing the water quality storage volume. The orifice plate or restriction plate is made of stainless steel and restricts the volume of water that can leave the basin in a given time. The person installing the plate should consult the Storm Water Pollution Prevention Plan (SWPPP) for which size orifice plate to install. Properly designed and maintained stormwater infrastructure helps make our rivers and streams a little cooler.

For more information, contact our office at 513.695.1337

Sediment and Erosion Control is an ongoing battle on construction sites. One day everything may be fine, silt fence is functioning, and sediment is being contained on site. But, the next day may bring inclement weather that moves sediment around and damages Best Management Practices (BMPs) for sediment and erosion control.  That’s why BMP maintenance on construction sites requires vigilance to ensure they are working to control sediment.
Recently, we got hit with a frosty snowstorm, dumping a foot of snow over Warren County. While the frozen ground may help reduce sediment runoff, there are still issues to combat. Work must continue, the roads need plowed, and sidewalks need cleared so that workers can continue to work on homes being built. So, there can be some slushy sediment that makes its way onto the streets during this time.
Dimitry Loukoumidis at Fischer Homes is well aware of the need to keep up on sediment and erosion control. Dimitri and Fischer Homes have been great to work with, consistently paying attention to site BMPs, and being communicative when Warren County SWCD site inspectors see something that needs maintenance. That’s why this month we are giving a shout-out to Fischer Homes at Losh Landing in Deerfield Township. There are always challenges with sediment for any development under construction, but Fischer Homes has been keeping up with their routine weekly street-sweeping schedule. Following this snowstorm, they are increasing their street sweeping from three days a week, to a daily basis for the sections where they are building homes. They have even coordinated with another builder in the community to coordinate their street sweeping schedules together.
 
Dimitri has provided a quote:
“One of the first things I was told at Fischer Homes was the importance of a clean and organized community. When we have potential customers driving and walking through communities, we do not want them to have to navigate mud, trash, and debris. We want them to see a well-organized community where everything has a place. We want their first impression of Fischer Homes to be positive and stand out from other builders in the area. This is especially important in communities like Losh Landing where we share the community with another builder. In order to achieve this high standard, I think that starts at the very beginning with proper sediment and erosion control. Not only does this prevent erosion from our sites and sediment getting into the roadways, it helps to protect our drainage swales, catch basins, and any surrounding properties and waterways, but it also sets clear boundaries. Whether our trade partners realize it or not, proper and consistent silt control sets clear boundaries of where they can and cannot drive, run equipment, etc. This directly impacts how much mud and debris is tracked on to the road and through the community.  In my opinion proper management of silt control and roadways are the foundation to successfully transforming a development into a community.”
 
Thank you to Fischer Homes for your hard work and here’s to a Happy New Year!

Article written by Justin Bedocs, Urban Program Specialist

The Industrial revolution saw a large amount of pollution being dumped into America’s waterways, and treatment plants were either non-existent or a far-cry compared to what they are today. The Cuyahoga River in Cleveland, Ohio was so polluted with toxic sludge that it caught fire, multiple times! The environmental revolution of the 1960s and 70s led to many environmental regulations, as people saw how poorly we were treating our environment and ecosystems. In 1948, the Federal Water Pollution Control Act became the first U.S. law to combat water pollution. This was amended in 1972 to become The Clean Water Act (CWA). The CWA has helped make the nation’s waters safer and cleaner, allowing communities to return to the water for swimming, fishing, and recreation. Environmental laws like the Clean Water Act aren’t going away. They are still needed to continue protecting America’s cherished natural resources for future generations.
The Clean Water Act established the National Pollutant Discharge Elimination System (NPDES). There are a multitude of pollutants that enter America’s waterways, so there are a multitude of permits regulating discharge to those waterways. The NPDES permit we will focus on today, is the Construction Stormwater General Permit (CSGP). This permit allows discharge of stormwater from construction sites, provided that certain treatment practices are installed during construction.

Why is Dirt so Dirty?
Sediment is the largest pollutant in Ohio’s lakes and streams, so the CSGP aims to reduce the amount of sediment-laden water being discharged from construction sites. Excessive sediment in waterways can cause fish kills and disrupt ecosystems. It clouds the water column and makes it hard for aquatic life to breathe and find food. Fertilizers, pesticides, herbicides, and other pollutants also bond with sediment. It turns out that Ma was right all along. Dirt is dirty. So, take your shoes off at the door!

When is the Permit Required?
We are currently in the sixth generation of the CSGP. This Ohio EPA permit (OHC000006) is required for any project that will disturb one or more acres of earth. It is required to discharge stormwater from the construction site when the ground is exposed to the elements and erosion occurs. More information regarding this permit can be found here.
To obtain coverage, the applicant must submit a Notice of Intent (NOI) to the Ohio EPA. Once this permit is received from the EPA, a Stormwater Pollution Prevention Plan and Earth Disturbing Permit (EDP) Application must be submitted to our office for review to ensure sediment and erosion control measures will be installed throughout the project. The EDP application can be found and submitted here. Our urban technicians inspect the site each month to make sure the permit requirements like sediment and erosion control measures are being upheld. When the project is complete and the site is stabilized, a Notice of Termination (NOT) must be filed to close out the permit coverage. These applications can be found in the Ohio EPA eBusiness Center Surface Water Tracking, Reporting, and Electronic Application Management System (STREAMS) here.

Who Is Responsible for Sediment and Erosion Controls?
The contact listed on the CSGP Notice of Intent (NOI) application or the designated SWPPP contact is responsible for upholding permit requirements and maintaining sediment and erosion control measures throughout the duration of the project. Sometimes it’s a building company that does the total site development and the construction. In other cases, there may be a developer who only does the grading, roads, and utilities, but then a builder comes in for the construction later. In this case, the permit coverage needs to be transferred to the builder(s). If there are multiple builders, each builder would need to sign up as a co-permittee to the overall site permit. That way, each builder is aware of their responsibility for individual lot controls to keep sediment contained.
In a situation where each house is a separate builder, and disturbance is less than one acre, the permit is still needed. Ohio EPA refers to this type of project as a Common Plan of Development (as defined in Appendix A of the CGP). This occurs when there is a contiguous area where multiple separate and distinct construction activities may be taking place at different times on different schedules under one common plan. There are two ways permit coverage can be transferred, Co-Permittee coverage and Individual lot coverage.
 
Co-Permittee Coverage
Co-permittees can be added to a permit if there are multiple developers or contractors working on a project that falls under one general permit and there are centralized sediment and erosion controls (controls that address runoff from one or more lots, I.e., a basin or ditches/inlets along roadways not associated with a specific developed lot). A common example of this is a large residential subdivision development with centralized storm control features that has different builders working on different sections/lots throughout the development. Without obtaining the co-permittee coverage for those different contractors, the original overall development permittee (typically developer/SWPPP contact) retains the responsibility of both the centralized sediment and erosion control measures and the individual lot controls. Therefore, adding those entities as co-permittees to the project transfers responsibility of individual lot controls maintenance to the builders/contractors and the developer retains responsibility of the centralized features.

Individual Lot Coverage
If there are no centralized storm control features and the transfer of permit coverage will not prevent or impair the implementation of controls, the original permittee can transfer responsibility to individual lot owners. In this case, the original permittee must temporarily stabilize sold lots, inform the new lot owner of his permit obligations, and ensure that an Individual Lot NOI application is submitted to the Ohio EPA at least seven (7) days prior to the date the new lot owner intends to accept permit responsibility.
 
In both the case of adding co-permittees and obtaining individual lot permit coverage, the lot owner should obtain a copy of the original SWPPP and comply with its requirements. Depending on site topography and location, additional controls above and beyond those outlined for the "typical" lot may be required. The new lot owner may also be partially or completely responsible for amending the SWPPP and installing those controls.

For more information please contact Warren SWCD at 513.695.1337

Winter is officially here! Well, not officially, but the time to stabilize construction sites for the winter is here!  The winter stabilization window listed in the Rainwater and Land Development window is November 1st through February 29th. Any areas that have exposed soil on an active construction site will need to be stabilized for the winter if the area will be dormant for 21 days or more over the winter. This month’s development digest on winter stabilization is a basic overview on why this BMP (Best Management Practice) is important, and the specifications of this stabilization practice.
Soil pollution is an issue that greatly affects the water that runs through Warren County. Soil pollution can be greatly increased in the winter due to the large amounts of snow, and melting of that snow, that creates water runoff. BMPs are practices we can put in place to minimize the risk of soil pollution. Winter stabilization is an important BMP that can help keep the soil out of the waters.

So, what exactly does winter stabilization entail? Winter stabilization can involve two different methods. The first method involves planting a dormant, cool season grass that will survive the winter and start its growth in the spring. Putting mulch down is also a necessary step to allow this method to be effective. The second method is to only put mulch down and not worry about the seed. This method may be more applicable if earthwork will resume directly at the end of winter when work starts back up. Both methods involve mulch, which is important because mulch provides a barrier between the stormwater and the exposed soil that help to keep the soil in place. Below are examples of types of mulch and types of grass seed that can be used.
 

Types of Mulch:        

• Straw                                                                                                
• Straw matting
• Wood chips
• Shredded woody material
• Pine needles
• Compost

 
Grass Species:

• Tall fescue
• Annual Ryegrass
• Perennial Ryegrass
• Kentucky Bluegrass

 
 
More information on temporary seeding throughout the year can be found on Table 7.8.1 of the Rainwater and Land Development Manual. For an area to be considered stable, 70% of the area should be seeded and mulched.
Stabilizing a site during the winter is the best method to prevent erosion and sediment runoff during a time of the year when work may not be happening. At the very least, dormant areas with exposed sediment should be mulched during the winter months. Further information on temporary stabilization techniques can be found on the Rainwater and Land Development Manual. Further information on stabilization regulations can be found in the Ohio Construction General Permit.
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Have questions on the topic of winter stabilization? Please feel free to reach out to our office through email at [email protected] or call us at (513) 695-1337.  

As cooler weather moves in, I hope you find time to kick back with a warm cup of your beverage of choice and this article considering Settling Time. For this article we will talk about different factors which impact how long it takes for particulates to settle out of stormwater once in the retention basin.

Stormwater retention basins are features that help to do the following:
*  Hold back water to help mitigate downstream flooding.
*  Settle out particulates to improve downstream water quality.
*  Slow down the rate of stormwater flow to help control erosion.
​*  Lower the temperature of the stormwater before it can flow downstream.​

As storm water flows over construction sites, parking lots and roads it picks up dirt and other debris that make up the suspended solids. The suspended solids can be sand, clay, silt and other particulates. The sediment load will vary based on the amount and duration of the rain event. Once the stormwater reaches the basin its flowrate drops off. In a quiescent pool the solids carried by the stormwater are given time to settle. If there is still flow through the pool or a second rain event occurs particulates may not have time to completely settle. These flow conditions would result in dynamic settling or possibly resuspension of sediment. Some particles are so small they will not settle. Others will have a settling time that is based on their particle size, shape, density and the water temperature. Solid settling in a stormwater basin can be estimated by Stokes’ Law.

Where:
V = settling velocity of the solid
g = acceleration of gravity (constant)
p1= mass density of the solid
p = mass density of water (constant)
d = diameter of the solid (assuming spherical shape)
µ= kinematic viscosity of water (varies only with temperature).

From the above equation we can see that particulates of higher mass density (p1) will settle out a bit more quickly than particles with lower mass density. (p1) We can also see that larger diameter (d2) particulates will settle out much faster than smaller particles. As diameter increases the settling velocity increases exponentially. Suspended solids vary in size with a particle of coarse sand being about 1,000x larger than a particle of fine clay. Given the larger diameter of the sand particles, we would expect them to settle much more rapidly than clay. Lastly temperature comes into play. Water becomes more viscous (µ) as temperature decreases. This higher viscosity leads to slower settling times.

Other factors come into play when considering settling time. Though the Stokes equation assumes that particles are round, few particles would be perfectly spherical. The irregular shaped particles would likely settle more slowly. Concentration of particles also plays a role. Like snowflakes falling from the sky, sediment particles can collide forming larger floc particles. These floc particles will settle more rapidly. In fact, flocculant is sometimes used to bond to suspended sediment or chemicals to sink them to the bottom and reduce the amount of polluted water leaving the basin. Chemical properties will also play a role. An extreme being road salt. The salt mineral is dense and of large diameter but will dissolve into the water. 

The dissolved road salt will not settle out of the stormwater. Particles with a greater attraction to water will settle out more slowly or will remain in solution.
A well designed and maintained basin will slow water and hold it long enough to allow sediment to drop out of solution. Oversizing a basin is one way to ensure plenty of settling time. Depth of the basin also comes into play by providing a large enough sediment storage zone. Maximizing the distance between the inflow and outflow helps maximize detention time. The challenge is designing a basin that will provide time for solids to settle, store sediment, minimize the valuable real estate it will take up and provide for easy maintenance down the road. 
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For more information contact our office at 513.695.1337

​You may have heard lately that Ohio is in a drought. A recently released drought map indicates Warren County to be in a severe to extreme drought. During these dry times, your construction site may welcome the lack of rain as dry sites can be easier to move around on and experience fewer issues with sediment and erosion control. However, we can’t get complacent on sediment and erosion control. The battle must go on!

In this month’s Development Digest, we will discuss remaining vigilant during dry times by having a routine dust control program in place, as well as making sure site BMPs are ready to go for the big rain. Dust can be a real problem during times of drought. So much so, that Soil and Water Conservation Districts were established to combat this issue, after the Great Dust Bowl of the 1930s. Poor farming practices, dry conditions, high winds, and plowing all combined to stir up the earth and create massive dust storms throughout the Midwest. President FDR signed the Soil Conservation Act of 1935 to protect our Country’s soil and water resources. This led to the establishment of the Ohio Soil and Water Conservation Commission (OSWCC) in 1941, which allowed funding to create Soil and Water Conservation Districts throughout the state. On construction sites, we often focus on keeping sediment contained during rain events, but soil loss can also occur during a drought. That’s why it’s important establish a dust control routine to keep sediment contained. Dust can be a real problem, as it is considered an airborne contaminant. Nearby existing homes and property can be covered in dust. It can become a public health concern when residents have trouble breathing. Our office has been receiving complaints from many sites throughout the county and we have been working with site contractors to ensure dust control measures are being enacted. 
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This can become a sleeping monster if dust control isn’t implemented. During times of extended drought, the ground becomes drier and harder. Especially in Warren County where much of the soil is clay, the ground can become like an impervious surface when it is compacted, dried and hardened. So, when it does eventually rain, the first initial downpour will likely run off the surface quickly, like it would on pavement. To further compound the issue, vehicles driving around on the site stirs up the sediment, creating dust clouds that will settle on the hard ground.  This fine-grained dust that settles accumulates almost like the regolith and dust on the surface of the moon. We are seeing anywhere from 1 to 3 inches of dust settled on some sites lately. 

4. Stone- Install crushed stone on graded roadways with construction traffic.
5. Barriers- Snow fencing or other suitable barriers may be placed perpendicular to wind currents to control air currents and blowing soil.
6. Calcium Chloride- the chemical may be applied by mechanical spreader as loose, dry granules. Follow manufacturer’s specs.
7. Operation and Maintenance- Repetitive, routine treatment of dust control practices.
8. Street Cleaning- Remove any settled dust from paved areas with a routine street sweeping schedule.

​Due to the recent drought, this is a great time to think about dust control. It looks like we will be getting some rain soon, so keep these practices in mind for the next dry time! If you have any questions regarding dust control you can contact us at the Warren County Soil and Water Conservation District website https://www.warrenswcd.com/ or by our phone number at (513) 695-1337.    

Additional Resources
 
Ohio EPA Rainwater and Land Development Manual. Chapter 7 Soil Stabilization – Dust Control: https://epa.ohio.gov/divisions-and-offices/surface-water/guides-manuals/rainwater-and-land-development?msclkid=cb5f60f4b48d11ec8b5ece1ef5e16d3c