Document ID: EPA-HQ-OW-2008-0465-2138
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2012-02-24T05:00Z

Appendix G – Buffer Guidance.

The purpose of this guidance is to assist you in complying with the
requirements in Part 2.1.2.1 of the permit regarding the establishment
of natural buffers or equivalent sediment controls.  This guidance is
organized as follows:

  TOC \o "1-4" \h \z \u    HYPERLINK \l "_Toc317064542"  G.1	 Sites That
Are Required to Comply with Part 2.1.2.1	  PAGEREF _Toc317064542 \h  2  

  HYPERLINK \l "_Toc317064543"  G.1.1	Step 1 - Determine if Your Site is
Within 50 Feet of a Surface Water	  PAGEREF _Toc317064543 \h  2  

  HYPERLINK \l "_Toc317064544"  G.1.2	Step 2 - Determine if Any
Exceptions to the Requirements in Part 2.1.2.1 Apply	  PAGEREF
_Toc317064544 \h  3  

  HYPERLINK \l "_Toc317064547"  G.2	 Compliance Alternatives Guidance	 
PAGEREF _Toc317064547 \h  4  

  HYPERLINK \l "_Toc317064548"  G.2.1 	Guidance for Providing and
Maintaining Natural Buffers	  PAGEREF _Toc317064548 \h  4  

  HYPERLINK \l "_Toc317064549"  G.2.1.1 Buffer Width Measurement	 
PAGEREF _Toc317064549 \h  5  

  HYPERLINK \l "_Toc317064550"  G.2.1.2	Limits to Disturbance Within the
Buffer	  PAGEREF _Toc317064550 \h  7  

  HYPERLINK \l "_Toc317064551"  G.2.1.3 Discharges to the Buffer	 
PAGEREF _Toc317064551 \h  7  

  HYPERLINK \l "_Toc317064552"  G.2.1.4 SWPPP Documentation	  PAGEREF
_Toc317064552 \h  8  

  HYPERLINK \l "_Toc317064553"  G.2.2	Guidance for Providing the
Equivalent Sediment Reduction as the 50-foot Buffer	  PAGEREF
_Toc317064553 \h  8  

  HYPERLINK \l "_Toc317064554"  G.2.2.1 Determine Whether it is Feasible
to Provide a Reduced Buffer	  PAGEREF _Toc317064554 \h  8  

  HYPERLINK \l "_Toc317064555"  G.2.2.2 Design Controls That Provide
Equivalent Sediment Reduction as 50-foot Buffer	  PAGEREF _Toc317064555
\h  8  

  HYPERLINK \l "_Toc317064556"  a.	Step 1 - Estimate the Sediment
Reduction from the 50-foot Buffer	  PAGEREF _Toc317064556 \h  9  

  HYPERLINK \l "_Toc317064557"  b.	Step 2 - Design Controls That Match
the Sediment Removal Efficiency of the 50-foot Buffer	  PAGEREF
_Toc317064557 \h  11  

  HYPERLINK \l "_Toc317064558"  G.2.3  	Small Residential Lot Compliance
Alternatives	  PAGEREF _Toc317064558 \h  12  

  HYPERLINK \l "_Toc317064559"  G.2.3.1	Step 1 – Determine if You are
Eligible for the Small Residential Lot Compliance Alternatives	  PAGEREF
_Toc317064559 \h  13  

  HYPERLINK \l "_Toc317064560"  G.2.3.2 Step 2 – Implement the
Requirements of the Small Residential Lot Compliance Alternative
Selected	  PAGEREF _Toc317064560 \h  13  

  HYPERLINK \l "_Toc317064561"  a.	Small Residential Lot Compliance
Alternative 1	  PAGEREF _Toc317064561 \h  13  

  HYPERLINK \l "_Toc317064562"  b.	Small Residential Lot Compliance
Alternative 2	  PAGEREF _Toc317064562 \h  14  

 



G.1	 Sites That Are Required to Comply with Part 2.1.2.1

The purpose of this part is to help you determine if the requirements in
Part 2.1.2.1 apply to your site. 

G.1.1	Step 1 - Determine if Your Site is Within 50 Feet of a Surface
Water

Part 2.1.2.1 applies to you only if your earth-disturbing activities
will occur within 50 feet of a surface water that receives stormwater
discharges from your site.    REF _Ref316371779 \h  Figure  G – 1
illustrates when a site would be required to comply with the
requirements in Part 2.1.2.1 due to their proximity to a surface water. 
If the surface water is not located within 50 feet of the
earth-disturbing activities, Part 2.1.2.1 does not apply.  

Figure G -   SEQ Figure_G_- \* ARABIC  1 . Example of earth-disturbing
activities within 50 feet of a surface water.

If you determine that your earth-disturbing activities will occur within
50 feet of a surface water that receives stormwater discharges from your
site, the requirements in Part 2.1.2.1 apply, except for certain
circumstances that are described in Step 2.

Note that where some natural buffer exists but portions of the area
within 50 feet of the surface water are occupied by preexisting
development disturbances, or if a portion of area within 50 feet of the
surface water is owned by another party and is not under your control,
the buffer requirements in Part 2.1.2.1 still apply, but with some
allowances. Clarity about how to implement the compliance alternatives
for these situations is provided in G.2.1.2 and G.2.2.2 below.

Note that EPA does not consider designed stormwater control features
(e.g., stormwater conveyance channels, storm drain inlets, stormwater
basins) that direct storm water to surface waters more than 50 feet from
the disturbance to constitute surface waters for the purposes of
determining if the buffer requirements apply.

G.1.2	Step 2 - Determine if Any Exceptions to the Requirements in Part
2.1.2.1 Apply

The following exceptions apply to the requirements in Part 2.1.2.1:

If there is no discharge of stormwater to surface waters through the
area between the disturbed portions of the site and any surface waters
located within 50 feet of your site, you are not required to comply with
the requirements in this Part. This includes situations where you have
implemented controls measures, such as a berm or other barrier, that
will prevent such discharges. 

Where no natural buffer exists due to preexisting development
disturbances (e.g., structures, impervious surfaces) that occurred prior
to the initiation of planning for the current development of the site,
you are not required to comply with the requirements in this Part. 

Where some natural buffer exists but portions of the area within 50 feet
of the surface water are occupied by preexisting development
disturbances, you are required to comply with the requirements in this
Part. For the purposes of calculating the sediment load reduction for
either compliance alternative 2 or 3 below, you are not expected to
compensate for the reduction in buffer function that would have resulted
from the area covered by these preexisting disturbances. Clarity about
how to implement the compliance alternatives for these situations is
provided in G.2.1.2 and G.2.2.2 below.

If during your project, you will disturb any portion of these
preexisting disturbances, the area removed will be deducted from the
area treated as natural buffer. 

For “linear construction projects” (see Appendix A), you are not
required to comply with this requirement if site constraints (e.g.,
limited right-of-way) prevent you from complying with the requirements
of the alternatives in Part 2.1.2.1a, provided that, to the extent
practicable, you limit disturbances within 50 feet of the surface water
and/or you provide supplemental erosion and sediment controls to treat
stormwater discharges from earth disturbances within 50 feet of the
surface water. You must also document in your SWPPP your rationale for
why it is infeasible for you to comply with the requirements in Part
2.1.2.1a, and describe any buffer width retained and/or supplemental
erosion and sediment controls installed. 

For “small residential lot” construction (i.e., a lot being
developed for residential purposes that will disturb less than 1 acre of
land, but is part of a larger residential project that will ultimately
disturb greater than or equal to 1 acre), you have the option of
complying with the requirements in Part G.2.3 of this appendix.

The following disturbances within 50 feet of a surface water are exempt
from the requirements in this Part:

Construction approved under a CWA Section 404 permit; or

Construction of a water-dependent structure or water access areas (e.g.,
pier, boat ramp, trail). 

Note that you must document in your SWPPP if any disturbances related to
any of the above exceptions occurs within the buffer area on your site. 

G.2	 Compliance Alternatives Guidance

If in Part G.1 of this guidance you determine that the buffer
requirements apply to your site, you have three compliance alternatives
from which you can choose:

Provide and maintain a 50-foot buffer undisturbed natural buffer (Part
2.1.2.1a.i); or

Provide and maintain an undisturbed natural buffer that is less than 50
feet and is supplemented by additional erosion and sediment controls,
which in combination achieves the sediment load reduction equivalent to
a 50-foot undisturbed natural buffer (Part 2.1.2.1a.ii);1 or

If it is infeasible to provide and maintain an undisturbed natural
buffer of any size, you must implement erosion and sediment controls
that achieve the sediment load reduction equivalent to a 50-foot
undisturbed natural buffer (Part 2.1.2.1a.iii).1 

The compliance alternative selected above must be maintained throughout
the duration of permit coverage.

The following provides detailed guidance for how you can comply with
each of the compliance alternatives.  Part G.2.1 below provides guidance
on how to provide and maintain natural buffers consistent with the
alternatives 1 and 2, above.  Part G.2.2 below provides guidance on how
to comply with the requirement to provide a 50-foot buffer equivalent
through erosion and sediment controls consistent with alternatives 2 and
3, above. 

G.2.1 	Guidance for Providing and Maintaining Natural Buffers

The following guidance is intended to assist you in complying with the
requirements to provide and maintain a natural buffer during
construction.  This part of the guidance applies to you if you choose
either alternative 1 (50-foot buffer) or alternative 2 (a buffer of < 50
feet supplemented by additional erosion and sediment controls that
achieve the equivalent sediment load reduction as the 50-foot buffer),
or if you are providing a buffer in compliance with one of the small
residential lot compliance alternatives in Part G.2.3 below.  

G.2.1.1 Buffer Width Measurement

Where you are retaining a buffer of any size, the buffer should be
measured perpendicularly from any of the following points, whichever is
further landward from the water:

1.	The ordinary high water mark of the water body, defined as the line
on the shore established by fluctuations of water and indicated by
physical characteristics such as a clear, natural line impressed on the
bank, shelving, changes in the character of soil, destruction of
terrestrial vegetation, and/or the presence of litter and debris; or

2.	The edge of the stream or river bank, bluff, or cliff, whichever is
applicable.

Refer to Figure G – 2 and   REF _Ref316371813 \h  Figure G - 3 .  You
may find that specifically measuring these points is challenging if the
flow path of the surface water changes frequently, thereby causing the
measurement line for the buffer to fluctuate continuously along the path
of the waterbody. Where this is the case, EPA suggests that rather than
measuring each change or deviation along the water’s edge, it may be
easier to select regular intervals from which to conduct your
measurement.  For instance, you may elect to conduct your buffer
measurement every 5 to 10 feet along the length of the water.

Additionally, note that if earth-disturbing activities will take place
on both sides of a surface water that flows through your site, to the
extent that you are establishing a buffer around this water, it must be
established on both sides.  For example, if you choose alternative 1
above, and your project calls for disturbances on both sides of a small
stream, you would need to retain the full 50 feet of buffer on both
sides of the water.  However, if your construction activities will only
occur on one side of the stream, you would only need to retain the
50-foot buffer on the side of the stream where the earth-disturbance
will occur. 

Figure G -   SEQ Figure_G_- \* ARABIC  2 . This image shows buffer
measurement from the ordinary high water mark of the water body, as
indicated by a clear natural line impressed on the bank, shelving,
changes in the character of the soil, destruction of terrestrial
vegetation, and/or the presence of litter/debris.

Figure G -   SEQ Figure_G_- \* ARABIC  3 . This image shows buffer
measurement from the edge of the bank, bluff, or cliff, whichever is
applicable.

G.2.1.2	Limits to Disturbance Within the Buffer

You are considered to be in compliance with this requirement if you
retain and protect from construction activities the natural buffer that
existed prior to the commencement of construction. If the buffer area
contains no vegetation prior to the commencement of construction (e.g.,
sand or rocky surface), you are not required to plant any additional
vegetation. As noted above, any preexisting structures or impervious
surfaces are allowed in the buffer provided you retain and protect from
disturbance the vegetation in the buffer outside the preexisting
disturbance.

To ensure that the water quality protection benefits of the buffer are
retained during construction, you are prohibited from conducting any
earth-disturbing activities within the buffer during permit coverage. 
In furtherance of this requirement, prior to commencing earth-disturbing
activities on your site, you must delineate, and clearly mark off, with
flags, tape, or a similar marking device, the buffer area on your site. 
The purpose of this requirement is to make the buffer area clearly
visible to the people working on your site so that unintended
disturbances are avoided.

While you are not required to enhance the quality of the vegetation that
already exists within the buffer, you are encouraged to do so where such
improvements will enhance the water quality protection benefits of the
buffer.  (Note that any disturbances within the buffer related to buffer
enhancement are permitted and do not constitute construction
disturbances.) For instance, you may want to consider targeted plantings
where limited vegetation exists, or replacement of existing vegetation
where invasive or noxious plant species (see  HYPERLINK
"http://plants.usda.gov/java/noxiousDriver"
http://plants.usda.gov/java/noxiousDriver ) have taken over.  In the
case of invasive or noxious species, you may want to remove and replace
them with a diversity of native trees, shrubs, and herbaceous plants
that are well-adapted to the climatic, soil, and hydrologic conditions
on the site.  You are also encouraged to limit the removal of naturally
deposited leaf litter, woody debris, and other biomass, as this material
contributes to the ability of the buffer to retain water and filter
pollutants.

If a portion of the buffer area adjacent to the surface water is owned
by another party and is not under your control, you are only required to
retain and protect from construction activities the portion of the
buffer area that is under your control.  For example, if you elect
alternative 1 above (provide and maintain a 50-foot buffer), but 10 feet
of land immediately adjacent to the surface water is owned by a
different party than the land on which your construction activities are
taking place and you do not have control over that land, you must only
retain and protect from construction activities the 40-foot buffer area
that occurs on the property on which your construction activities are
taking place. EPA would consider you to be in compliance with this
requirement regardless of the activities that are taking place in the
10-foot area that is owned by a different party than the land on which
your construction activities are taking place that you have no control
over.  

G.2.1.3 Discharges to the Buffer

You must ensure that all discharges from the area of earth disturbance
to the natural buffer are first treated by the site’s erosion and
sediment controls (for example, you must comply with the Part 2.1.2.2
requirement to establish sediment controls around the downslope
perimeter of your site disturbances), and if necessary to prevent
erosion caused by stormwater flows within the buffer, you must use
velocity dissipation devices. The purpose of this requirement is to
decrease the rate of stormwater flow and encourage infiltration so that
the pollutant filtering functions of the buffer will be achieved. To
comply with this requirement, construction operators typically will use
devices that physically dissipate stormwater flows so that the discharge
entering the buffer is spread out and slowed down.  

G.2.1.4 SWPPP Documentation

You are required to document in your SWPPP the natural buffer width that
is retained.  For example, if you are complying with alternative 1, you
must specify in your SWPPP that you are providing a 50-foot buffer.  Or,
if you will be complying with alternative 2, you must document the
reduced width of the buffer you will be retaining (and you must also
comply with the requirements in Part 2.1.2.1c to describe the erosion
and sediment controls you will use to achieve an equivalent sediment
reduction, as described in Part G.2.2 below).  Note that you must also
show any buffers on your site plan in your SWPPP consistent with Part
7.2.6.3.  Additionally, if any disturbances related to the exceptions in
Part 2.1.2.1e occur within the buffer area, you must document this in
the SWPPP.  

G.2.2	Guidance for Providing the Equivalent Sediment Reduction as the
50-foot Buffer 

If you are selecting Alternative 2 (provide and maintain a buffer that
is less than 50 feet that is supplemented by additional erosion and
sediment controls that, together, achieve the equivalent sediment load
reduction as the 50-foot buffer) or Alternative 3 (implement erosion and
sediment controls that achieve the equivalent sediment load reduction as
the 50-foot buffer), the following guidance is intended to assist you in
demonstrating that you will achieve the equivalent sediment reduction as
the 50-foot buffer.

G.2.2.1 Determine Whether it is Feasible to Provide a Reduced Buffer

EPA recognizes that there will be a number of situations in which it
will be infeasible to provide and maintain a buffer of any width.  While
some of these situations may exempt you from the buffer requirement
entirely (see G.1.2), if you do not qualify for one of these exemptions,
there still may be conditions or circumstances at your site that make it
infeasible to provide a natural buffer.  For example, there may be sites
where a significant portion of the property on which the
earth-disturbing activities will occur is located within the buffer
area, thereby precluding the retention of natural buffer areas.  EPA
believes there are likely to be other examples of situations that make
it infeasible to provide any buffer area.

Therefore, in choosing between the 2 different compliance alternatives
(Alternative 2 or 3), you should only elect to comply with Alternative 2
if it is feasible for you to retain any natural buffer on your site. 
(Note:  For any buffer width retained, you are required to comply with
the requirements in Part G.2.1, above, concerning the retention of
vegetation and restricting earth disturbances.) Similarly, if you
determine that it is infeasible to provide a natural buffer of any size
during construction, you should elect to comply with Alternative 3. 
After making this determination, you should proceed to Part G.2.2.2 to
determine how to provide controls that, together with any buffer areas
that is being retained, if applicable, will achieve an equivalent
sediment load reduction as the 50-foot buffer.

G.2.2.2 Design Controls That Provide Equivalent Sediment Reduction as
50-foot Buffer

You must next determine what additional controls must be implemented on
your site that, alone or in combination with any retained natural
buffer, achieve a reduction in sediment equivalent to that achieved by a
50-foot buffer.  

Note that if only a portion of the natural buffer is less than 50 feet,
you are only required to implement erosion and sediment controls that
achieve the sediment load reduction equivalent to the 50-foot buffer for
discharges through that area.  You would not be required to provide
treatment of stormwater discharges that flow through 50 feet or more of
natural buffer. See   REF _Ref316548400 \h  Figure G - 4 .

Figure G -   SEQ Figure_G_- \* ARABIC  4  Example of how to comply with
the requirement to provide the equivalent sediment reduction when only a
portion of your earth-disturbances discharge to a buffer of less than
50-feet.

To comply with this requirement, you are required to do the following:

Step1 - Estimate the sediment reduction expected from your site if you
had retained a 50-foot natural buffer;

Step 2 - Design controls that alone or in combination with any width of
buffer retained achieve the equivalent sediment removal efficiency as
that expected from the 50-foot buffer; and

Step 3 - Document in your SWPPP how your controls will achieve the
equivalent sediment removal efficiency of the 50-foot buffer.

Guidelines to help you work through these requirements are provided
below.

Step 1 - Estimate the Sediment Reduction from the 50-foot Buffer 

In order to design controls that match the sediment removal efficiency
of a 50-foot buffer, you first need to know what this efficiency is for
your site.  The sediment removal efficiencies of natural buffers vary
according to a number of site-specific factors, including precipitation,
soil type, land cover, slope length, width, steepness, and the types of
sediment controls used to reduce the discharge of sediment prior to the
buffer.  EPA has simplified this calculation by developing buffer
performance tables covering a range of vegetation and soil types for the
areas covered by the CGP.  See Attachment 1, Tables G - 8 through G -
15.  Note: buffer performance values in Tables G - 8 through G - 15
represent the percent of sediment captured through the use of perimeter
controls (e.g., silt fences) and 50-foot buffers at disturbed sites of
fixed proportions and slopes.  

Using Tables G - 8 through G - 15 (see Attachment 1), you can determine
the sediment removal efficiency of a 50-foot buffer for your geographic
area by matching the vegetative cover type that best describes your
buffer area and the type of soils that predominate at your site.  For
example, if your site is located in Massachusetts (Table G - 9), and
your buffer vegetation corresponds most closely with that of tall fescue
grass, and the soil type at your site is best typified as sand, your
site’s sediment removal efficiency would be  81 percent.  

In this step, you should choose the vegetation type in the tables that
most closely matches the vegetation that would exist naturally in the
buffer area on your site regardless of the condition of the buffer.
However, because you are not required to plant any additional vegetation
in the buffer area, in determining what controls are necessary to meet
this sediment removal equivalency in Step 2 below, you will be able to
take credit for this area as a fully vegetated “natural buffer.” 

Similarly, if a portion of the buffer area adjacent to the surface water
is owned by another party and is not under your control, you can treat
the area of land not under control as having the equivalent vegetative
cover and soil type that predominates on the portion of the property on
which your construction activities are occurring.  

For example, if your earth-disturbances occur within 50 feet of a
surface water, but the 10 feet of land immediately adjacent to the
surface water is owned by a different party than the land on which your
construction activities are taking place and you do not have control
over that land, you can treat the 10 foot area adjacent to the stream as
having the equivalent soil and vegetation type as predominates in the 40
foot area under your control.  You would then make the same assumption
in Step 2 for purposes of determining the equivalent sediment removal.

Alternatively, you may do your own calculation of the effectiveness of
the 50-foot buffer based upon your site-specific conditions, and may use
this number as your sediment removal equivalency standard to meet
instead of using Tables G - 8 through G - 15. This calculation must be
documented in your SWPPP.

Step 2 - Design Controls That Match the Sediment Removal Efficiency of
the 50-foot Buffer

Once you have determined the estimated sediment removal efficiency of a
50-foot buffer for your site in Step 1, you will be required to select
stormwater controls that will provide an equivalent sediment load
reductions.  These controls can include the installation of a single
designed control, such as a sediment pond, additional perimeter
controls, or other type of device.  Alternatively, you may elect to
install a combination of stormwater controls and to retain some amount
of a buffer.  Whichever control(s) you select, you must demonstrate in
your SWPPP that the controls will provide at a minimum the same sediment
removal capabilities as the 50-foot buffer (Step 1). You are allowed to
take credit for the removal efficiencies of your required perimeter
controls in your calculation of equivalency, because these were included
in calculating the buffer removal efficiencies in tables G - 8 through G
- 15.  (Note: You are reminded that the controls must be kept in
effective operating condition until you have completed final
stabilization on the disturbed portions of the site discharging to the
surface water.)

To make the determination that your controls and/or buffer area achieve
an equivalent sediment load reduction as the 50-foot buffer, you will
need to use a model or other type of calculator.  As mentioned above,
there are a variety of models available that can be used to support your
calculation, including USDA’s RUSLE-series programs and the WEPP
erosion model, SEDCAD, SEDIMOT, or other models.  A couple of examples
are provided in Attachment 3 to help illustrate how this determination
could be made.

If you are retaining a buffer of less than 50 feet, you may take credit
for the removal that will occur from the reduced buffer and only need to
provide additional controls to make up the difference between the
removal efficiency of a 50 foot buffer and the removal efficiency of the
narrower buffer.  For example, if you are retaining a 30 foot buffer,
you can account for the sediment removal provided by the 30-foot buffer
retained, and you will only need to design controls to make up for the
additional removal provided by the 20-foot of buffer that is not being
provided. To do this, you would plug the width of the buffer that is
retained into RUSLE or another model, along with other stormwater
controls that will together achieve a sediment reduction equivalent to a
natural 50-foot buffer.

As described in Step 1 above, you can take credit for the area you have
retained as a “natural buffer” as being fully vegetated, regardless
of the condition of the buffer area.  

For example, if your earth-disturbances occur 30 feet from a surface
water, but the 10 feet of land immediately adjacent to the surface water
is owned by a different party than the land on which your construction
activities are taking place and you do not have control over that land,
you can treat the 10-foot area as a natural buffer, regardless of the
activities that are taking place in the area. Therefore, you can assume
(for purposes of your equivalency calculation) that your site is
providing the sediment removal equivalent of a 30-foot buffer, and you
will only need to design controls to make up for the additional removal
provided by the 20-foot of buffer that is not being provided. 

Step 3 - Document How Site-Specific Controls Will Achieve the Sediment
Removal Efficiency of the 50-foot Buffer 

In Steps 1 and 2, you determined both the expected sediment removal
efficiency of a 50-foot buffer at your site, and you used this number as
a performance standard to design controls to be installed at your site,
which alone or in combination with any retained natural buffer, achieves
the expected sediment removal efficiency of a 50-foot buffer at your
site. The final step is to document in your SWPPP the information you
relied on to calculate the equivalent sediment reduction as an
undisturbed natural buffer.

EPA will consider your documentation to be sufficient if it generally
meets the following:

–	For Step 1, refer to the table in Attachment 1 that you used to
derive your estimated 50-foot buffer sediment removal efficiency
performance.  Include information about the buffer vegetation and soil
type that predominate at your site, which you used to select the
sediment load reduction value in Tables G - 8 through G - 15.  Or, if
you conducted a site-specific calculation for sediment removal
efficiency, provide the specific removal efficiency, and the information
you relied on to make your site-specific calculation. 

–	For Step 2:  (1) Specify the model you used to estimate sediment
load reductions from your site; and (2) the results of calculations
showing how your controls will meet or exceed the sediment removal
efficiency from Step 1.

If you choose Alternative 3, you must also include in your SWPPP a
description of why it is infeasible for you to provide and maintain an
undisturbed natural buffer of any size.

G.2.3  	Small Residential Lot Compliance Alternatives

In this part of Appendix G, EPA provides additional compliance
alternatives for operators of small residential lots.  In accordance
with Part 2.1.2.1e.iv, operators of small residential lots who do not
provide a 50-foot buffer are not required to make the demonstration
outlined in Part G.2.2.2.  Instead, qualifying operators can comply with
the buffer requirement by choosing to implement a set of traditional
sediment and erosion controls from the menu of practices provided in
Part G.2.3.2.      

EPA has developed two different alternatives for compliance.  The
following steps describe how a small residential lot operator would
achieve compliance with these 2 alternatives.  

G.2.3.1	Step 1 – Determine if You are Eligible for the Small
Residential Lot Compliance Alternatives

In order to be eligible for the small residential lot compliance
alternatives, the following conditions must be met:

The lot or grouping of lots meets the definition of “small residential
lot”; and 

The operator must comply with all other requirements in Part 2.1.2.1,
including:

Ensure that all discharges from the area of earth disturbance to the
natural buffer are first treated by the site’s erosion and sediment
controls, and use velocity dissipation devices if necessary to prevent
erosion caused by stormwater within the buffer; 

Document in the SWPPP the natural buffer width retained on the property,
and show the buffer boundary on your site plan; and

Delineate, and clearly mark off, with flags, tape, or other similar
marking device, all natural buffer areas.

G.2.3.2 Step 2 – Implement the Requirements of the Small Residential
Lot Compliance Alternative Selected

You must next choose from one of two small residential lot compliance
alternatives and implement the stormwater control practices associated
with that alternative.    

Note:  The compliance alternatives provided below are not mandatory. 
Operators of small residential lots can alternatively choose to comply
with the any of the options that are available to other sites in Part
2.1.2.1a, described in Parts G.2.1 and G.2.2 in this appendix.

Small Residential Lot Compliance Alternative 1 

Alternative 1 is a straightforward tiered- technology approach that
specifies the controls that a small residential lot must implement based
on the buffer width retained.  To achieve compliance with Alternative 1,
you must implement the controls specified in Table G – 1 based on the
buffer width to be retained. See footnote 3, below, for a description of
the controls you must implement.

For example, if you are an operator of a small residential lot that will
be retaining a 35-foot buffer and you choose Small Residential Lot
Compliance Alternative 1, you must implement double perimeter controls
between earth disturbances and the surface water. 

In addition to implementing the applicable control, you must also
document in your SWPPP how you will comply with Alternative 1.

Table G -   SEQ Table_G_- \* ARABIC  1 . Alternative 1 Requirements  

Retain ≤ 30 foot Buffer

No Additional Requirements	Double Perimeter Controls	Double Perimeter
Controls and 7-Day Site Stabilization

Small Residential Lot Compliance Alternative 2

Alternative 2 specifies the controls that a builder of a small lot must
implement based on both the buffer width retained and their risk of
sediment discharge.  By incorporating the sediment risk, this approach
may result in the implementation of controls that are more appropriate
for the site’s specific conditions. 

Step 1 – Determine Your Site’s Sediment Risk Level

To meet the requirements of Alternative 2, you must first determine your
site’s sediment discharge “risk level” based on the site’s
slope, location, and soil type. To help you to determine your site’s
sediment risk level, EPA has developed five different tables for
different slope conditions. You must select the table that most closely
corresponds to your site’s average slope. 

For example, if your site’s average slope is 7 percent, you would use
Table G – 4 to determine your site’s sediment risk. 

After you determine which table applies to your site, you must then use
the table to determine the “risk level” (e.g., “low”,
“moderate”, or “high”) that corresponds to your site’s
location and predominant soil type. 

For example, based on Table G - 3, a site located in New Hampshire with
a 4 percent average slope and with predominately sandy clay loam soils
would fall into the “moderate” risk level. 

of ≤ 3 Percent

                             Soil Type

and ≤ 6 Percent

                             Soil Type

 Location	Clay	Silty Clay Loam or Clay-Loam	Sand	Sandy Clay Loam, Loamy
Sand or Silty Clay	Loam, Silt, Sandy Loam or Silt Loam

Guam	Moderate	Moderate	Moderate	Moderate	High

Puerto Rico 	Moderate	Moderate	Moderate	Moderate	High

Virgin Islands	Moderate	Moderate	Moderate	Moderate	High

American Samoa	High	High	Moderate	High	High

Massachusetts and New Hampshire	Moderate	Moderate	Low	Moderate	High

Idaho	Low	Low	Low	Low	Low

New Mexico	Low	Low	Low	Low	Moderate

Washington D.C.	Moderate	Moderate	Moderate	Moderate	High

 

 Percent and ≤ 9 Percent

                               Soil Type

≤ 15 Percent

                               Soil Type

 Location	Clay	Silty Clay Loam or Clay-Loam	Sand	Sandy Clay Loam, Loamy
Sand or Silty Clay	Loam, Silt, Sandy Loam or Silt Loam

Guam	High	High	High	High	High

Puerto Rico 	High	High	High	High	High

Virgin Islands	Moderate	High	Moderate	High	High

American Samoa	High	High	High	High	High

Massachusetts and New Hampshire	Moderate	Moderate	Moderate	Moderate	High

Idaho	Low	Low	Low	Low	Low

New Mexico	Low	Moderate	Low	Moderate	Moderate

Washington D.C.	Moderate	High	Moderate	Moderate	High

Table G -   SEQ Table_G_- \* ARABIC  6 . Risk Levels for Sites with
Average Slopes of > 15 Percent

                               Soil Type

 Location	Clay	Silty Clay Loam or Clay-Loam	Sand	Sandy Clay Loam, Loamy
Sand or Silty Clay	Loam, Silt, Sandy Loam or Silt Loam

Guam	High	High	High	High	High

Puerto Rico 	High	High	High	High	High

Virgin Islands	High	High	High	High	High

American Samoa	High	High	High	High	High

Massachusetts and New Hampshire	High	High	Moderate	High	High

Idaho	Low	Low	Low	Low	Moderate

New Mexico	Moderate	Moderate	Moderate	Moderate	High

Washington D.C.	High	High	Moderate	High	High

Step 2 – Determine Which Additional Controls Apply

Once you determine your site’s “risk level”, you must next
determine the additional controls you need to implement on your site,
based on the width of buffer you plan to retain.  Table G - 7 specifies
the requirements that apply based on the “risk level” and buffer
width retained.  See footnote 3, above, for a description of the
additional controls that are required.

For example, if you are the operator of a small residential lot that
falls into the “moderate” risk level, and you decide to retain a
20-foot buffer, using Table G-7 you would determine that you need to
implement double perimeter controls to achieve compliance with Part
2.1.2.1. 

You must also document in your SWPPP your compliance with Alternative 2.

Table G -   SEQ Table_G_- \* ARABIC  7 . Alternative 2 Requirements2

Retain ≥ 50’ Buffer	Retain <50’ and >30’ Buffer	Retain ≤30’ 
and >10’ Buffer	Retain ≤ 10’ Buffer

Low Risk	No Additional Requirements 	No Additional Requirements	Double
Perimeter Control	Double Perimeter Control

Moderate Risk	No Additional Requirements	Double Perimeter Control	Double
Perimeter Control	Double Perimeter Control and 7-Day Site Stabilization

High Risk	No Additional Requirements	Double Perimeter Control	Double
Perimeter Control and 7-Day Site Stabilization	Double Perimeter Control
and 7-Day Site Stabilization 



ATTACHMENT 1

Sediment Removal Efficiency Tables

EPA recognizes that very high removal efficiencies, even where
theoretically achievable by a 50-foot buffer, may be very difficult to
achieve in practice using alternative controls.  Therefore in the tables
below, EPA has limited the removal efficiencies to a maximum of 90%. 
Efficiencies that were calculated at greater than 90% are shown as 90%,
and this is the minimum percent removal that must be achieved by
alternative controls.

Table G -   SEQ Table_G_- \* ARABIC  8 . Estimated 50-foot Buffer
Performance in Idaho*

	Estimated % Sediment Removal

Type of Buffer Vegetation**	Clay	Silty Clay Loam or Clay-Loam	Sand	Sandy
Clay Loam, Loamy Sand or Silty Clay	Loam, Silt, Sandy Loam or Silt Loam

Tall Fescue Grass	42	52	44	48	85

Medium-density Weeds	28	30	28	26	60

Low-density Warm-season Native Bunchgrass (i.e., Grama Grass)	25	26	24
24	55

Northern Mixed Prairie Grass	28	30	28	26	50

Northern Range Cold Desert Shrubs	28	28	24	26	50

* Applicable for sites with less than nine percent slope

** Characterization focuses on the under-story vegetation

Table G -   SEQ Table_G_- \* ARABIC  9 . Estimated 50-foot Buffer
Performance in Massachusetts and New Hampshire* 

	Estimated % Sediment Removal

Type of Buffer Vegetation**	Clay	Silty Clay Loam or Clay-Loam	Sand	Sandy
Clay Loam, Loamy Sand or Silty Clay	Loam, Silt, Sandy Loam or Silt Loam

Warm-season Grass (i.e., Switchgrass, Lemongrass)	79	90	90	90	90

Cool-season Dense Grass (Kentucky Bluegrass, Smooth Bromegrass, Timothy)
78	90	90	90	90

Tall Fescue Grass	76	90	81	89	90

Medium-density Weeds	66	76	60	72	66

* Applicable for sites with less than nine percent slope

** Characterization focuses on the under-story vegetation

Table G -   SEQ Table_G_- \* ARABIC  10 . Estimated 50-foot Buffer
Performance in New Mexico*  

	Estimated % Sediment Removal

Type of Buffer Vegetation **	Clay	Silty Clay Loam or Clay-Loam	Sand
Sandy Clay Loam, Loamy Sand or Silty Clay	Loam, Silt, Sandy Loam or Silt
Loam

Tall Fescue grass	71	85	80	86	90

Medium-density Weeds	56	73	55	66	78

Low-density Warm-season Native Bunchgrass (i.e., Grama Grass)	53	70	51
62	67

Southern Mixed Prairie Grass	53	71	52	63	50

Southern Range Cold Desert Shrubs	56	73	55	65	53

* Applicable for sites with less than nine percent slope

** Characterization focuses on the under-story vegetation

Table G -   SEQ Table_G_- \* ARABIC  11 . Estimated 50-foot Buffer
Performance in Washington, DC*   

	Estimated % Sediment Removal

Type of Buffer Vegetation **	Clay	Silty Clay Loam or Clay-Loam	Sand
Sandy Clay Loam, Loamy Sand or Silty Clay	Loam, Silt, Sandy Loam or Silt
Loam

Warm-season Grass (i.e., Switchgrass, Lemongrass)	82	90	90	90	90

Cool-season Dense Grass (Kentucky Bluegrass, Smooth Bromegrass, Timothy)
81	90	90	90	90

Tall Fescue Grass	79	90	83	89	90

Medium-density Weeds	71	79	66	75	74

* Applicable for sites with less than nine percent slope

** Characterization focuses on the under-story vegetation

Table G -   SEQ Table_G_- \* ARABIC  12 . Estimated 50-foot Buffer
Performance in American Samoa*  

	Estimated % Sediment Removal

Type of Buffer Vegetation **	Clay	Silty Clay Loam or Clay-Loam	Sand
Sandy Clay Loam, Loamy Sand or Silty Clay	Loam, Silt, Sandy Loam or Silt
Loam

Bahiagrass (Permanent cover)	82	90	90	90	83

Warm-season Grass (i.e., Switchgrass, Lemongrass)	82	90	90	90	85

Dense Grass	82	90	90	90	83

Tall Fescue Grass	82	89	82	89	79

Medium-density Weeds	70	73	62	75	59

* Applicable for sites with less than nine percent slope

** Characterization focuses on the under-story vegetation

Table G -   SEQ Table_G_- \* ARABIC  13 . Estimated 50-foot Buffer
Performance in Guam*  

	Estimated % Sediment Removal

Type of Buffer Vegetation **	Clay	Silty Clay Loam or Clay-Loam	Sand
Sandy Clay Loam, Loamy Sand or Silty Clay	Loam, Silt, Sandy Loam or Silt
Loam

Bahiagrass (Permanent cover)	80	90	90	90	89

Warm-season Grass (i.e., Switchgrass, Lemongrass)	80	90	90	90	90

Dense Grass	79	90	90	90	89

Tall Fescue Grass	76	90	80	88	87

Medium-density Weeds	63	73	53	68	61

* Applicable for sites with less than nine percent slope

** Characterization focuses on the under-story vegetation

Table G -   SEQ Table_G_- \* ARABIC  14 . Estimated 50-foot Buffer
Performance in Puerto Rico*   

	Estimated % Sediment Removal

Type of Buffer Vegetation**	Clay	Silty Clay Loam or Clay-Loam	Sand	Sandy
Clay Loam, Loamy Sand or Silty Clay	Loam, Silt, Sandy Loam or Silt Loam

Bahiagrass (Permanent cover)	83	90	90	90	90

Warm-season Grass (i.e., Switchgrass, Lemongrass)	83	90	90	90	90

Dense Grass	83	90	90	90	90

Tall Fescue Grass	82	90	84	90	89

Medium-density Weeds	72	78	65	76	64

* Applicable for sites with less than nine percent slope

** Characterization focuses on the under-story vegetation

Table G -   SEQ Table_G_- \* ARABIC  15 . Estimated 50-foot Buffer
Performance in Virgin Islands*   

Type of Buffer Vegetation**	Clay	Silty Clay Loam or Clay-Loam	Sand	Sandy
Clay Loam, Loamy Sand or Silty Clay	Loam, Silt, Sandy Loam or Silt Loam

Bahiagrass (Permanent cover)	85	90	90	90	90

Warm-season Grass (i.e., Switchgrass, Lemongrass)	86	90	90	90	90

Dense Grass	85	90	90	90	90

Tall Fescue Grass	85	90	88	90	89

Medium-density Weeds	75	77	71	78	63

* Applicable for sites with less than nine percent slope

** Characterization focuses on the under-story vegetation

ATTACHMENT 2

Using the Sediment Removal Efficiency Tables – Questions and Answers

– 	What if my specific buffer vegetation is not represented in Tables
G - 8 through G - 15?  Tables G - 8 through G - 15 provide a wide range
of factors affecting buffer performance; however, there may be instances
where the specific buffer vegetation type on your site is not listed. 
If you do not see a description of the type of vegetation present at
your site, you should choose the vegetation type that most closely
matches the vegetation type on your site.  You can contact your local
Cooperative Extension Service Office ( HYPERLINK
"http://www.csrees.usda.gov/Extension" www.csrees.usda.gov/Extension )
for assistance in determining the vegetation type in Tables G - 8
through G - 15 that most closely matches your site-specific vegetation. 

–	What if there is high variability in local soils?  EPA recognizes
that there may be a number of different soil type(s) on any given
construction site.  General soil information can be obtained from USDA
soil survey reports ( HYPERLINK "http://websoilsurvey.nrcs.usda.gov"
http://websoilsurvey.nrcs.usda.gov ) or from individual site assessments
performed by a certified soil expert.  Tables G - 8 through G - 15
present eleven generic soil texture classes, grouping individual
textures where EPA has determined that performance is similar.  If your
site contains different soil texture classes, you should use the soil
type that best approximates the predominant soil type at your site.

–	What if my site slope is greater than 9 percent after final grade is
reached?  As indicated in the buffer performance tables, the estimated
sediment removal efficiencies are associated with disturbed slopes of up
to 9 percent grade.  Where your graded site has an average slope of
greater than 9 percent, you should calculate a site-specific buffer
performance.

–	How do I calculate my own estimates for sediment reduction at my
specific site?  If you determine that it is necessary to calculate your
own sediment removal efficiency using site-specific conditions (e.g.,
slopes at your site are greater than 9 percent), you can do so by
choosing from a range of available mathematical models that are
available to facilitate this calculation, including USDA’s
RUSLE-series programs and the WEPP erosion model, SEDCAD, SEDIMOT, or
other equivalent models.  

–	What is my estimated buffer performance if my site location is not
represented by Tables G - 8 through G - 15?  If your site is located in
an area not represented by Tables G - 8 through G - 15, you should use
the table that most closely approximates conditions at your site.  You
may also choose to conduct a site-specific calculation of the buffer
performance.

–	What if only a portion of my site drains to the buffer area?  If
only a portion of your site drains to a surface water, where that water
is within 50 feet of your construction activities, you are only required
to meet the equivalency requirement for the stormwater flows
corresponding to those portions of the site.  See Example 2 below for an
example of how this is expected to work.



ATTACHMENT 3

Examples of How to Use the Sediment Removal Efficiency Tables

Example 1. Comparatively Wet Location (7.5 acre site located in
Massachusetts)

The operator of a 7.5-acre construction site in Massachusetts has
determined that it is infeasible to establish a buffer of any size on
their site, and is now required to select and install controls that will
achieve an equivalent sediment load reduction as that estimated in G - 9
for their site conditions.  The first step is to identify what
percentage of eroded sediment is estimated to be retained from a 50-foot
buffer.  For this example, it is assumed that the site has a relatively
uniform gentle slope (3 percent), so Table G - 9 can be used to estimate
the 50-foot buffer sediment load reduction.  If the site’s buffer
vegetation is best typified by cool-season dense grass and the
underlying soil is of a type best described as loamy sand, the 50-foot
buffer is projected to capture 90 percent of eroded sediment from the
construction site.

The second step is to determine what sediment controls can be selected
and installed in combination with the perimeter controls already
required to be implemented at the site (see Part 2.1.2.2), which will
achieve the 90 percent sediment removal efficiency from Table G - 9. 
For this example, using the RUSLE2 profile model, it was determined that
installing a pair of shallow-sloped diversion ditches to convey runoff
to a well-designed and maintained sediment basin provides 99 percent
sediment removal.  Because the estimated sediment reduction is greater
than the required 90 percent that a 50-foot buffer provides, the
operator will have met the buffer requirements. See   REF _Ref316371865
\h  Figure G - 5 .  The operator could also choose a different set of
controls, as long as they achieve at least a 90 percent sediment removal
efficiency.

Figure G -   SEQ Figure_G_- \* ARABIC  5 .  Example 1 – Equivalent
Sediment Load Reductions at a 7.5 ac Site in MA.

Example 2.  Arid Location With Pre-existing Disturbances in the Natural
Buffer (6.5 acre site located in New Mexico)

An operator of a site in New Mexico determines that it is not
practicable to provide a 50-foot buffer, but a 28-foot buffer can be
provided.  Because the operator will provide a buffer that is less than
50 feet, the operator must determine which controls, in combination with
the 28-foot buffer, achieve a sediment load reduction equivalent to the
50-foot buffer. In this example, the project will disturb 6.5 acres of
land, but only 1.5 acres of the total disturbed area drains to the
buffer area.  Within the 28-foot buffer area is a preexisting concrete
walkway. Similar to Example 1, the equivalence analysis starts with Step
1 (Part G.2.2.2) with a review of the New Mexico buffer performance
(Table G - 10).  The operator determines that the predominate vegetation
type in the buffer area is prairie grass and the soil type is similar to
silt, and that the site is of a uniform, shallow slope (e.g., 3 percent
grade). Although the operator will take credit for the disturbance
caused by the concrete walkway as a natural buffer in Step 2, here the
operator can treat the entire buffer area as being naturally vegetated
with prairie grass. Based on this information, the operator refers to
Table G - 10 to estimate that the 50-foot buffer would retain 50 percent
of eroded soil.

The second step is to determine, based on the 50 percent sediment
removal efficiency found in Table G - 10, what sediment controls in
combination with the 28-foot buffer area, can be implemented to reduce
sediment loads by 50 percent or more. The operator does not have to
account the reduction in buffer function caused by the preexisting
walkway, and can take credit for the entire 28-foot buffer being fully
vegetated in the analysis. For this example, using the RUSLE2 profile
model, the operator determined that installing a fiber roll barrier
between the silt fence (already required by Part 2.1.2.2) and the
28-foot buffer will achieve an estimated 84 percent sediment removal
efficiency. See   REF _Ref316371882 \h  Figure G - 6 .  Note that this
operator is subject to the requirement in Part 2.1.2.1b.i to ensure that
discharges through the silt fence, fiber roll barrier, and 28-foot
buffer do not cause erosion within the buffer.  The estimated sediment
reduction is greater than the required 50 percent; therefore the
operator will have met the buffer alternative requirement.

Figure G -   SEQ Figure_G_- \* ARABIC  6 .  Example 2 – Equivalent
Sediment Load Reductions at a 6.5 ac Site in NM.

 EPA used the following when developing the buffer performance tables:

The sediment removal efficiencies are based on the U.S. Department of
Agriculture’s RUSLE2 (“Revised Universal Soil Loss Equation 2”)
model for slope profiles using a 100-foot long denuded slopes.

Sediment removal was defined as the annual sediment delivered at the
downstream end of the 50-foot natural buffer (tons/yr/acre) divided by
the annual yield from denuded area (tons/yr/acre).

As perimeter controls are also required by the CGP, sediment removal is
in part a function of the reduction due to a perimeter control (i.e.,
silt fence) located between the disturbed portion of the site and the
upstream edge of the natural buffer and flow traveling through a 50-foot
buffer of undisturbed natural vegetation.

It was assumed that construction sites have a relatively uniform slope
without topographic features that accelerate the concentration for
erosive flows.

It was assumed that vegetation has been removed from the disturbed
portion of the site and a combination of cuts and fills have resulted in
a smooth soil surface with limited retention of near-surface root mass

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luation of buffer performance.  To represent different types of buffer
vegetation, EPA evaluated 4 or more common vegetative types for each
state/territory covered under the permit. For each vegetation type
evaluated, EPA considered only permanent, non-grazed and non-harvested
vegetation, on the assumption that a natural buffer adjacent to the
surface water will typically be undisturbed.  EPA also evaluated slope
steepness and found that sediment removal efficiencies present in Tables
G -8 through G - 15 are achievable for slopes that are less than nine
percent.

  Description of Additional Controls Applicable to Small Residential Lot
Compliance   Alternatives 1 and 2:

No Additional Requirements: If you implement a buffer of 50 feet or
greater, then you are not subject to any additional requirements. Note
that you are required to install perimeter controls between the
disturbed portions of your site and the buffer in accordance with Part
2.1.2.2.

Double Perimeter Control: In addition to the reduced buffer width
retained on your site, you must provide a double row of perimeter
controls between the disturbed portion of your site and the surface
water spaced a minimum of 5 feet apart. 

Double Perimeter Control and 7-Day Site Stabilization: In addition to
the reduced buffer width retained on your site and the perimeter control
implemented in accordance with Part 2.1.2.2, you must provide a double
row of perimeter controls between the disturbed portion of your site and
the surface water spaced a minimum of 5 feet apart, and you are required
to complete the stabilization activities specified in Parts 2.2.1.2a
and/or 2.2.1.2b within 7 calendar days of the temporary or permanent
cessation of earth-disturbing activities.

  One source for determining your site’s predominant soil type is the
USDA’s Web Soil Survey located at  HYPERLINK
"http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx"
http://websoilsurvey.nrcs.usda.gov/app/WebSoilSurvey.aspx .  

 The buffer performances were calculated based on a denuded slope
upgradient of a 50-foot buffer and a perimeter controls, as perimeter
controls are a standard requirement (see Part 2.1.2.2). 

February 15, 2012

G -  PAGE   \* MERGEFORMAT  1  of 24

A small residential lot is a lot or grouping of lots being developed for
residential purposes that will disturb less than 1 acre of land, but
that is part of a larger residential project that will ultimately
disturb greater than or equal to 1 acre.