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

Fall-time in southwestern Ohio is simply wonderful; the weather starts to cool down and the trees transform into a lovely autumn palette. Around this time of year, we like to remind developers to continue seeding as much bare soil as possible before winter turns the corner.
Soil erosion remains an area of concern for earth disturbing work throughout winter as melting snowfall transports sediment into our local waterways. According to the Ohio Rainwater and Land Development Manual, soil stabilization is the most effective way to minimize sediment erosion from construction sites (over >90%). We mean it when we say seeding and sod installation is music to our ears!

Temporary seeding (which must be applied to bare soil where additional work is not scheduled for more than 14 days) may continue until November 1st. Especially through late fall, we recommend monitoring and maintaining seeding efforts until an overall vegetative density of >70% has been achieved. Fall-time seeding species include Rye, Tall Fescue, Annual and Perennial Ryegrass, Creeping Red Fescue, and Kentucky Bluegrass. A layer of mulch (straw, wood cellulose fiber, and/or mulch matting) must be applied during or immediately after seeding. During more favorable seeding times of year, mulching may not be necessary but late fall weather warrants the extra protection.

The window for permanent seeding (which must be applied to bare soil at final grade that may be idle for over 1 year) has now closed (March 1st through September 30th). Click here for our guide to dormant seeding during winter months. Traditional permanent seeding efforts may germinate during late fall, but they are unlikely to survive the winter.
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Spotlight Example from the Field: Seeding Before Winter
Ryan Wilms and his team at Cincinnati United Contractors have been working on improvements at Green Bay Packaging in Lebanon, OH. During routine inspections, we noticed their team’s excellent pre-winter stabilization. Having this steep slope stabilized now will set them up for success throughout winter. This also allows for more efficient sediment management throughout the rest of their project.

What if temporary/final grading work took longer than expected and you missed the seeding window? Although the disturbed areas cannot be traditionally seeded after the windows have closed, bare soils must be mulched or dormant seeded.

For more specific technical guidance and specifications, please review the most recent OEPA Construction General Permit (OHC000006), the Rainwater and Land Development Manual, and the Stormwater Pollution Prevention Plan (SWPPP) for your site.

Additional Resources
Construction Site Winterization – Development Digest
Rainwater and Land Development Manual
Ohio EPA NPDES General Construction Permit (OHC000006)
Seeding Tables – USDA NRCS