City of Scottsbluff Hires New Stormwater Specialist

The City of Scottsbluff recently named Leann Sato as Stormwater Program Specialist.  Leann replaces Annie Folck, who was promoted to City Planner.  Leann is anxious to continue Scottsbluff’s Stormwater public education and outreach programs with her background in mass communication, training and development, and teaching.   She looks forward to working with the community and agencies to employ good Stormwater practices.  If you have any stormwater related projects with which you would like assistance, please feel free to contact Leann at (308) 630-8011 or lsato@scottsbluff.org.

Construction Bulletin April 2014

Goals for Construction Site Runoff Management

Ahh, Spring— warmer weather, thawing ground, and afternoon rain showers.   While welcoming the change of season,  it’s also time to consider Best Management Practices (BMPs) for keeping the soil on site and preventing stormwater run off and sediment pollution.

The ultimate goal for construction site runoff management is to prevent the pollution of stormwater runoff.  Best Management Practices (BMPs) aim to slow the velocity, control the volume, and/or  filter  site run– off.  Stormwater permits require BMPs to address erosion and sediment run-off, soil exposure, ground disturbance, compaction,  buffers,  outlet protection, and stabilization.  Below are some BMPs to consider for construction sites.

Grass

Stabilization, or planting ground cover,  allows run off to infiltrate the ground providing nutrients to the plants and replenishing ground water. Stabilization is required by the Nebraska general construction permit as soon as practicable on sites and no more than 14 days after construction activities have ceased.

 

Slope Drain

When the slope is steep channeling the runoff through a slope drain can be an effective erosion control.  Drains may be made of pipe,  s shown, or a constructed channel lined with rock,  turf replacement mats,  and wattles to slow the flow of water.

 

Flexible Gutter

Flexible rain gutters can direct roof water away from exposed soil.  The gutters can channel water to impermeable areas (e.g. concrete driveways) where clean stormwater can run to the gutter or to vegetated areas where plants and soil can absorb the water

InspectionRegular inspection,  every 14 days and within 24 hours of a 1/2” rain event,  is the best way to insure construction site BMPs are working effectively.  Look for evidence, or  potential,  of pollutants entering the drainage system.  An inspection report must be identify any incidents of non-compliance with permit conditions and actions taken to correct the issue.  If no incidents of non-compliance were found, the report must contain a certification that the site is in compliance with the Storm Water Pollution Prevention Plan (SWPPP). The  reports should be retained with the SWPPP for up to three years after the permit expires or is terminated.

 

 

Construction BMPs: Hazardous Materials Storage

Many materials used on construction sites can be classified as hazardous materials.  Some of the most common include fuel, oil, paint, concrete curing compounds, asphalt products, pesticides, herbicides, and septic wastes. The proper storage and handling of these materials is essential to good stormwater management. Every SWPPP should include procedures for hazardous material handling and storage as well as procedures for spill response and reporting.  For more information about both these topics, see below: Continue reading Construction BMPs: Hazardous Materials Storage

Construction BMPs: Temporary Stabilization

This straw mulch has been crimped into the ground for temporary stabilization.

Stabilization, or establishing ground cover to protect disturbed soils from erosion, is not only a good practice, it is required by law.  The Nebraska state Construction General Permit states that, with a few exceptions such as snow cover or frozen ground conditions, “stabilization measures  must be initiated as soon as practicable in portions of the site where construction activities have temporarily or permanently ceased, but in no case more than 14 days after the construction activity in that portion of the site has temporarily or permanently ceased.” Since it is unlikely that suitable vegetation can be established within 14 days, other methods of stabilization must be considered.  Covering exposed or disturbed areas protects the soil from raindrop impact, slows the flow of and infiltrates stormwater, and protects newly seeded areas.  It also helps retain soil moisture, which will help your vegetation become established more quickly.

One of the simplest methods of erosion control is mulching.  Straw or hay mulch should be applied at a rate of 2-3 tons per acre.  To provide good ground cover, at least 50% of the mulch should be ten inches in length or longer.  The mulch should be crimped using a weighted roller that anchors the mulch into the soil.  If the area is seeded before the mulch is applied, this can be a very simple and effective method of preventing erosion while vegetation is established.

Another method of erosion control is a rolled erosion control blanket.  These can be made from natural or synthetic materials and can be effective in protecting steeper slopes from erosion.  They are designed to be rolled onto the area and stapled into place.  Always follow installation specifications, as poor installation can cause these products to fail. 

This erosion contol blanket temporarily stabilizes the slope while vegetation is established.

If the blanket is not properly anchored and stapled, it can either be washed away or stormwater can wash out soil underneath the blanket, causing small gullies that are difficult to seed.  If the area is seeded and the erosion control blanket is installed correctly, grass will grow up through the blanket, and over time, the blanket will degrade.

For extremely steep slopes or areas with limited access, hydraulic mulching should be considered.  In this process, a slurry made up of mulch, seed, and a tackifying agent is sprayed onto the disturbed area.  There are also many other products and stabilization methods available.  Each site should be carefully evaluated to determine which product or combination of products is the most effective and economical way to achieve stabilization. 

 

 

 

 

Nebraska Construction Storm Water General Permit: Terminating Permit Coverage

If you have a stormwater permit (state or local) in your name, it is very important to close out that permit upon completion of a project.  As long as that permit is open, you are the responsible party for any stormwater discharges coming from your site.  A permit may be closed out under only two circumstances: either final stabilization must be achieved, or the permit must be transferred to another Operator or the Owner. 

Under the first circumstance, coverage under a NPDES construction permit may be terminated 180 calendar days after all soil disturbing construction activity has been completed, final stabilization has been achieved, and all temporary BMPs (silt fence, inlet protection, etc.) have been removed.  In order for a site to be considered stabilized, any areas that are not impervious (covered by buildings or pavement), must be vegetated with 70% perennial groundcover.  Annual vegetation, such as cover crops, do not count as final stabilization.  A simple test to see if you have 70% vegetation is to take a 100 foot long tape measure, lay it out over an area that is representative of the whole site, and count how many plants (in most cases blades of grass) coincide with the 1-foot marks.  If there are plants at 70 or more of these marks, then you have the required stabilization.  After final stabilization has been achieved for 180 calendar days, you may then file a Notice of Termination (NOT) which will terminate your permit coverage.  

The alternative method of terminating permit coverage is to transfer the permit to another Operator or the Owner.  In order to do this, you must file a Construction Storm Water Notice of Transfer (CSW-Transfer) that lists the current permit authorization number and the portion of the project that is to be transferred.  It is possible to retain responsibility for only part of a project, but to transfer a portion of the project to the new owner.  The person to whom you are transferring the permit is then required to submit a Notice of Intent (NOI) to the state, and the current permittee may now file an NOT.

There is often some confusion over who is eligible to take over responsibility for a Construction General Permit.  The permittee must be either the owner or operator of the site.  This means that the general contractor for a project is eligible to hold the permit.  If for some reason the general contractor changes during the course of the project, the permit may be transferred to the new Operator.  However, subcontractors, such as landscapers, are not allowed to take responsibility for the permit, because they do not meet the definition of “operator” for the project.  If a contractor’s portion of a project is complete and they want to terminate their permit coverage before final stabilization is completed, then their only option is to transfer permit coverage to the owner.  The new permittee will then be responsible for all inspections and best management practices required by the Construction General Permit.

If you ever have any questions about the permitting process, contact your local stormwater coordinator.  Contact information for the ten communities in NebraskaH2O can be found under the Communities tab on this website. 

 

Construction BMPs: Concrete Washout

This is an effective, inexpensive concrete washout.

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.

 

Construction BMPs: Inlet Protection

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.

There are numerous products available for purchase for protecting your inlets

 

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.

Silt fence keeps sediment out of area inlets

 

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.

Curb sock slows the flow of stormwater in curb line before it reaches 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

Construction BMPs: Silt Fence

Silt Fence

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:

The slicing method of installing silt fence

Installation– Silt fence is designed to pool water on your site while sediment settles out of it. Continue reading Construction BMPs: Silt Fence