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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.
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| Figure 1. Example Slope With Combination of Best Management Practices |
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| Figure 2. Sample Plan With Implementation Schedule |
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| Figure 3. Sample Details |
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.
Example 1
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
Example 2
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
Example 3
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
Example 4
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
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| Figure 4. Standardized BMPs |
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| Figure 5. Example Inlet Protection |
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| Figure 6. Example Tracking Control |
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
- Tradesheets
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.
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| Figure 7. Example Sanitary Facilities |
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.
Conclusions
Compliance with stormwater regulations is not easy. However,
all regulatory requirements are important because the impacts of
non-compliance can be damaging.
Penalties can be harsh,
so it is important to take informal and formal enforcement notices
seriously. Good planning, proper implementation, and maintenance
are key, and good housekeeping goes a long way toward compliance
and protection of the environment.
Carol L. Forrest,
P.E., CPESC, CPSWQ, is with GeoSyntec Consultants.
GEC
- July/August 2005
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