For obvious reasons concrete trucks should never be washed out into the street or into the storm drain. Solids that are washed out of the concrete trucks can clog storm drains, causing flooding and expensive clean-up. However, it is also important to contain the concrete wash water as well. The wash water is very alkaline, which means it has a very high pH. Water must have a pH in the range of 6.5-9.0 in order for aquatic life to survive. Concrete wash water typically has a pH of 12 or above. Furthermore, the pH scale is logarithmic, meaning that a pH of 12 is 10 times greater than a pH of 11, 100 times greater than a pH of 10, and 1000 times greater than a pH of 9.0, which is the highest level of alkalinity that aquatic life can tolerate. If allowed to escape the site, concrete wash water can have a severe effect on our streams and rivers.
Other significant pollutants in concrete wash water are heavy metals such as chromium. If wash water that is high in heavy metals leaches through the soil to the water table, it can contaminate our groundwater, which is where most cities in Nebraska get all of their drinking water.
Concrete washout is also high in suspended and dissolved solids. The average stream or river in the United States typically has a suspended solid count of no more than 60 parts per million (ppm). The average suspended solids in concrete wash water is 27,000 ppm, well above the range at which aquatic life can survive.
Luckily, it is not very difficult to control concrete washout on your construction site. There are several different ways to build a concrete washout facility, the most simple being to dig a pit and line it with plastic sheeting that is at least 10-mil thick. If you don’t have a good location on your site for a facility like this, you can also build a portable facility by building a box with a liner to contain the washout. There are also several products available for purchase that are effective, portable concrete washout containers.
Always locate concrete washouts as far away from storm drains as possible. Make sure they are clearly labeled and that drivers know where they are supposed to wash out. By doing this, we can make sure that one of the biggest pollutants from construction sites does not reach our waterways.
The planted area you see pictured below is a bioswale. A bioswale is a long, often linear depression in the ground that allows water to move from one location to another. It has gentle side slopes where plants can be grown to slow water enough to filter pollutants and allow more runoff to filter into the ground. This bioswale collects all the water from the roof of the library and directs it to the storm drain at the bottom of the swale. Roof runoff often carries many pollutants, such as leaf litter, bacteria and algae that grow in gutters, and bird droppings. The plants in the bioswale will help remove these pollutants before the runoff enters the storm sewer system, where it travels directly to theNorth Platte River.
This bioswale was the Eagle Scout project for Spencer Lake. Lake worked with the City of Scottsbluff to complete the project with help from members of Boy Scout Troop 13 and the UNL Master Gardeners. The project was designed by Amy Seiler and was funded in part with grant funds from the Greener Nebraska Towns Initiative and in part by the Lied Scottsbluff Public Library Foundation. The day of the installation, we had 29 volunteers work for a combined 100 hours.
Scroll through our pictures below for more information on this project.
Did you know that once every two and a half minutes someone calls a poison control center to report exposure to a household cleaning substance?1 Over half of these calls involve the exposure of a child under five years old.2 Most of us have several different kinds of toxic substances in our homes, including cleaning supplies, paint thinner, pesticides, etc. Not only are these products toxic while inside your home, if not disposed of properly, they can also be toxic to the environment. Continue reading Household Hazardous Wastes
Inlet protection is the last line of defense in preventing sediment from entering storm drain inlets and reaching our waterways. It should never be used as the only Best Management Practice (BMP), and often, if it fails, it is because there is not enough stormwater controls above the inlet to keep sediment on site. One of the common misconceptions about inlet protection is that it is meant to completely block off the inlet. Inlet protection should NEVER completely block off an inlet; not only can this be a safety hazard by flooding the roadway, it is ineffective because the sediment-laden water will just pass by to the next inlet. Instead, inlet protection is meant to slow the water flowing in the curb, shallowly pooling it to allow some of the sediment to drop out. Inlet protection can be constructed from rock socks, sediment control logs, silt fence, block and rock socks, or other materials. There are also numerous proprietary products available. The type of inlet protection you choose should depend on where your inlet is located.
Inlet protection in sump conditions
For inlets located in a sump, that is, at the low point of an area or a curb, it is important that the inlet continue to function during larger runoff events. For curb inlets, the maximum height of the protective barrier should be lower than the top of the curb opening to allow overflow into the inlet during larger storms. For area inlets, silt fence or other materials can be used to keep sediment-laden water out of the inlet. Just remember that if there is no overflow to the inlet, your site will experience some localized flooding.
Inlet Protection on Grade
If you inlet is located on a sloped street, instead of blocking off the inlet, you might try using curb socks in the flow line of the gutter uphill from the inlet. This will slow down the stormwater and give the sediment a chance to drop out before it reaches the inlet without blocking off the inlet.
For more information on inlet protection, see design details here from the Urban Drainage and Flood Control District IP-1 Urban Storm Drainage Criteria Manual Volume 3
The City of Scottsbluff has been selected by the Nebraska Forest Service as a member community in the Greener Nebraska Towns (GNT) Program. This program is designed to improvethe long-term sustainability of member communities. Scottsbluff will be receiving a total of $55,000 in grant funding, $30,000 of which will be allocated to tree planting, and $25,000 of which is to be spent on waterwise landscaping and stormwater management. We will be implementing demonstration projects that incorporate sustainable landscaping, tree planting, and stormwater best management practices, such as rain gardens, bioswales, and porous pavement. We will also be working with residents to plant trees and improve irrigation efficiency. Stay tuned to hear more about everything that we will be undertaking as part of this initiative!
Silt fence can be a very effective best management practice if it is used correctly. However, it is also one of the most misused and overused BMPs. Using silt fence incorrectly is not only ineffective, it can also be expensive. Here are some tips for using silt fence appropriately:
Note: This post describes the rain garden demonstration project which was installed in Scottsbluff in July 2010 with the help of the UNL Extension Stormwater Team. The garden is located on the corner of 19th Street and Avenue B.
Step 1 Choosing the Site
Rain gardens are designed to catch runoff from roofs, driveways, streets, sidewalks, or other areas of the lawn. This was an excellent site for a rain garden because of the downspout that drains into the area. Minimum work was needed to channel the runoff into the rain garden. Continue reading How to Install a Rain Garden