The National Pollutant Discharge Elimination System (NPDES) stormwater regulations for construction sites have been in place since 1990, but as soon as the Phase II regulations that lowered the trigger from 5 acres of disturbance to 1 acre of disturbance went into effect in 2003, we entered an era of increased litigation by environmental groups and enforcement by the regulators, as well as increased concern and confusion by the regulated construction and development community.
Most state general NPDES construction permits now require that an “effective combination of erosion and sediment control measures” be implemented on a construction site at all times. What does that mean? What are effective erosion and sediment control measures, and what is an effective combination of erosion and sediment control measures? Well, we know what it doesn’t mean. We know that only running silt fence around the perimeter of a site, as used to be commonly done, is no longer enough.
We also know that the regulators are well informed and understand the functional difference between erosion control and sediment control measures and expect both to be deployed on a site.
Erosion Versus Sediment Control
As a quick recap of the functional differences in control measures, erosion control is any practice that protects the soil surface and prevents the soil particles from being detached by the actions of wind or water. Erosion control, therefore, is a source control that treats the soil as a resource that has value and should be kept in place. Sediment control is any practice that traps soil particles after they have been detached and moved by wind or water. Sediment control measures are usually passive systems that rely on filtering or settling the particles out of the wind or water that is transporting them.
Which are more effective? Erosion control measures are preferred because they keep the soil in place and enhance protection of the site resources. When possible, erosion control measures should be used as the primary protection with sediment controls as the secondary system.
Problems on Construction Sites
What are the prevalent erosion problems on construction sites?
- Inappropriate best management practice (BMP) selection or design
- Improper BMP installation
- Inappropriate or inadequate BMP maintenance
- BMP failure (although this is rare)
- Poor vegetation growth
- Unforeseen climatic conditions
In combining BMPs for optimal performance to avoid these problems, it is important to include BMPs in every key category: erosion control practices, sediment control practices, drainage control practices, tracking control practices, wind erosion control practices, and non-stormwater pollution control practices.
Planning and Design
Informed planning and design should be considered as your first BMP. Choose from new and old erosion and sediment control technologies; employ new performance data to make good decisions; and combine BMPs for optimal performance. Good erosion and sediment control planning should result in an effective combination of erosion and sediment control measures.
When developing an effective stormwater pollution prevention plan (SWPPP) or erosion and sediment control plan (ESCP), the process should include:
- Adapting the BMPs to the resources available
- Understanding the site conditions
- Creating a realistic, practical, easily understood, and easily implemented plan
- Selecting measures that are cost-effective and consider all relevant criteria
- Combining BMPs to provide “layers of insurance”
During design, the plan developer should consider that the BMP system should have:
- Flexibility to change as site conditions change
- An effective maintenance program
- Monitoring of BMP performance and offsite impacts
Above all, one should avoid “cookie-cutter SWPPPs.”
We frequently talk to engineers who prepare plans without ever visiting the site. This can lead to major problems. A plan that was effective on one site will not necessarily be effective on another site because every site is different: different soils, different topography, different rainfall, different drainage patterns, different receiving waters, and different critical areas. One must understand these site-specific conditions to prepare an effective plan.
Effective Combination of Erosion and Sediment Control
Let’s provide a few examples of what we mean by an effective combination of control measures.
A new, high-embankment (fill) slope will be constructed to support a road during the rainy season. The BMPs should include:
- Track walking the slope to provide soil roughness and slow runoff
- Installing fiber rolls on contour to reduce the slope length
- Applying blown straw mulch or other source control to protect the slope surface
- Constructing a brow ditch at top of slope to prevent gullying
- Installing a sediment control barrier at toe of slope to trap sediment
A site has predominantly clayey soils. The BMPs should include:
- Relying on source controls to keep the soil in place
- Stabilizing the construction entrance and limiting vehicle ingress and egress
- Considering using a tire wash facility
- Regularly street sweeping or vacuuming
- Installing inlet protection
- Installing perimeter control along the site boundary
In constructing a retaining wall along a road that parallels a sensitive creek, the BMPs should include:
- Identifying and protecting the environmentally sensitive areas
- Installing perimeter control or vegetative buffer between the creek and construction site
- Temporarily diverting the creek
- Stabilizing disturbed areas promptly with blown straw mulch or other source control
Vegetation has been removed by fire and homes, and storm drains have survived but are vulnerable to high sediment loads. The BMPs should include:
- Inlet protection
- Toe-of-slope protection
- Slope interrupter devices to slow runoff
- Erosion control measures to hold soil in place until vegetation recovers
- Temporary check dams to slow flow in concentrated drainages
- High-end erosion control and buffers to protect sensitive areas and values at risk
Tools to Consider
What are some of the other tools and techniques that can be used to enhance cost-effective compliance with the NPDES construction regulations? One tool that is being used more and more is Internal Compliance Audits. These consist of performing an internal, independent review of compliance to identify vulnerabilities on construction sites, provide recommendations for rainy-season preparedness, and provide consistency within and among sites.
Other tools to consider include:
- Template SWPPP or ESCP and guidance document for users
- Standardized BMPs
- Standardized BMP lot designs
The template SWPPP or ESCP is not intended to preclude the engineer or plan preparer from using good judgment or original thought. Instead, it is intended to provide appropriate language and elements that will withstand legal challenges and regulatory scrutiny.
We frequently find plans that are missing a key component, and a template SWPPP or ESCP helps preclude this from happening.
The standardized BMPs are intended to provide consistency to contractors in BMP specifications and details. There are many BMP manuals available, and they may provide different specifications and details for the same measure. Additionally, many BMP manuals include information that is of more value to the engineer or designer than the contractor. The purpose of the standardized BMPs is to present standardized specifications and details for use by contractors throughout one of many projects to facilitate effective implementation of erosion and sediment control measures and reduce construction-related water-quality impacts. Additionally, the standardized BMPs should include non-stormwater pollution control measures.
The standard BMP lot designs are a tool that some developers are using to gain consistency among sites. The standard BMP lot designs are based on stage of construction, type of construction, and geographic location. They are simple, 8.5- by 11-inch plans that are easily understood.
Another tool to consider is the use of tradesheets, which are water-quality guidelines for the various subcontractor trades that are on a construction site, particularly during vertical construction. They target the framers, roofers, painters, stucco appliers, landscapers, and members of other construction trades who have a high turnover of personnel on the site and a high potential to pollute stormwater runoff. Tradesheets should be simple (one page), bilingual as appropriate, and enforceable by being included in the contract documents.
Avoiding Enforcement Actions
Now, with all those great tools, how do you avoid enforcement actions and survive increased regulatory scrutiny? Based on audits of hundreds of construction sites across the country, here are the regulatory “hot buttons”:
- Inadequate documentation
- Inadequate combination of erosion and sediment control measures
- Tracking offsite
- Trash and debris onsite
- Poorly managed washouts (concrete, paint, and stucco)
- Poorly placed and managed sanitary facilities (Porta-Johns)
- Inadequate BMP maintenance
Inadequate documentation includes the SWPPP or ESCP not being current, inspections and repairs not documented, and training not documented.
The contractor should keep a progress map on the wall of the construction trailer that shows the current state of BMP deployment that is dated and color-coded. Notations should be made if a BMP is temporarily removed or an alternative BMP is substituted. Supplementing the progress map with timely photographs, both ground and aerial, can help the contractor provide visual backup to enforcement personnel of his stormwater pollution prevention activities.
An inadequate combination of erosion control measures is readily apparent by reliance on sediment controls, or offsite discharges of sediment-laden stormwater runoff. An effective combination includes source control measures with sediment control barriers as the last line of defense before runoff leaves the site.
Tracking offsite, one of the biggest sources of public complaint about a construction site, is a way to attract unwanted regulatory scrutiny. Keeping the construction entrance stabilized and clean is an ongoing effort that pays off by giving an impression of good housekeeping on a site. It includes limiting access points, stabilizing the entrance, using a tire wash where necessary, and sweeping the street.
Trash and debris needs to be continually controlled and picked up on the site. Adequate numbers, types, and locations of trash containers are important. Trash containers should be solid-bottomed and able to be covered.
Washouts for concrete, paint, and stucco need to be provided throughout the site at appropriate locations (with signage) and properly maintained.
Sanitary facilities should be located off the street (for safety purposes) and provided with secondary containment. In areas of high winds, they should be secured to the ground.
Inadequate BMP maintenance is evidenced by eroded soils, tattered silt fence, damaged inlet protection, and fiber rolls or gravel bags damaged by vehicles. Labor and materials should always be kept onsite for rapid deployment, and repairs should be made within 48 hours of an inspection.
Training and awareness for personnel on a construction site are key. Training should be formal and informal and occur on an ongoing basis. All training should be documented.
Classroom training should include how to prepare an effective ESCP or SWPPP, NPDES refresher training, how to install and maintain BMPs, and hands-on field training on proper BMP installation and inspection. Other good forums for water-quality discussions and training include weekly tailgate or safety meetings. Every site should include informative and bilingual signage on adherence to NPDES regulations, location and use of washouts, and protection of BMPs from damage.
Compliance with stormwater regulations is not easy. However, all regulatory requirements are important because the impacts of non-compliance can be damaging.