1. BMP 5.6.1: Minimize Total Disturbed Area - Grading
      1. Water Quality Functions
      2. Stormwater Functions
      3. Key Design ElementsPotential Applications
    1. Description
    2. Detailed Stormwater Functions
    3. Design Considerations
      1. 1. Identify and Avoid Special Value/Sensitive Areas (see BMP 5.4.1)
      2. 2. Minimize Disturbance at Site
      3. 3. Minimize Disturbance at Lot
      4. 4. Maximize Soil Restoration
      5. 5. Minimize Construction Traffic Areas
      6. 6. Minimize Stockpiling and Storage Areas
    4. Construction Issues
    5. Cost Issues
      1. Site Clearing
      2. Strip Topsoil and Stockpile
      3. Site Preparation, Fine Grading, Seeding
    6. Stormwater Management Calculations
    7. Specifications

BMP 5.6.1: Minimize Total Disturbed Area - Grading
Without changing the building program, you can reduce site grading, removal
of existing vegetation (clearing and grubbing) and total soil disturbance. This
eliminates the need for re-establishment of a new maintained landscape for
the site and lot-by-lot, by modifying the proposed road system and other
relevant infrastructure as well as the building location and elevations to better
fit the existing topography.
Water Quality Functions
TSS:
TP:
NO3:
40%
0%
0%
Volume Reduction:
Recharge:
Peak Rate Control:
Water Quality:
High
High
High
High
Stormwater Functions
Key Design Elements
Potential Applications
Residential:
Commercial:
Ultra Urban:
Industrial:
Retrofit:
Highway/Road:
Yes
Yes
Limited
Yes
Limited
Limited
.
Identify and avoid special value and environmentally sensitive
areas
.
Minimize overall disturbance at the site
.
Minimize disturbance at the individual lot level
.
Maximize soil restoration to restore permabilities
.
Minimize construction-traffic locations
.
Minimize stockpiling and storage areas
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Description
This Non-Structural BMP assumes that the special value and sensitive resource areas have been
identified on a given development parcel and have been protected, and that clustering and area wide
concentration of uses also have been considered and included in the site design. All of these BMPs
serve to reduce site grading and to minimize disturbance/minimize maintenance. This BMP specifically
focuses on how to minimize the grading and overall site disturbance required to build the desired
program while maximizing conservation of existing site vegetation.
Reduction of site disturbance by grading can be accomplished in several ways. The requirements of
grading for roadway alignment (curvature) and roadway slope (grade) frequently increase site
disturbance throughout a land development site and on individual lots. Most land development plans
are formulated in 2-dimensional plan, based on the potential zoned density, and seldom consider the
constraints presented by topographic variation (slope) on the site. The layout and design of internal
roadways on a land development site with significant topographic variation (slope) can result in
extensive earthwork and vegetation removal (i.e., grading). Far less grading and a far less disruptive
site design can be accomplished if the site design is made to better conform with the existing
topography and land surface, where road alignments strive to follow existing contours as much as
possible, varying the grade and alignment criteria as necessary to comply with safety limits.
Site design criteria have evolved in municipalities to make sure that developments meet safety
standards (sight distance, winter icing, and so forth) as well as certain quality or appearance standards.
A common perception among municipal officials is that little deviation should be allowed in order to
maintain the integrity of the community. In fact, roadway design criteria should be made flexible in
order to better fit a given parcel and achieve a more “fluid” roadway alignment. The avoidance of
sensitive site features, such as important woodlands,
may be facilitated through flexible roadway layout.
Additionally, rigorous parcel criteria (front footage,
property setbacks, etc.) often add to this “plane
geometry” burden. Although the rectilinear grid layout
is the most efficient in terms of maximizing the number
of potential lots created at a development site, the end
result is a “cookie cutter” pattern normally found in
residential sites and the “strip” development found in
most highway commercial districts, all of which are apt
to translate into significant resource loss.
From the perspective of a single lot, the municipally-
required conventional lot layout geometry can also
impose added earthwork and grading that could be
avoided. Lot frontage criteria, yard criteria, and driveway criteria force the placement of a structure in
the center of every lot, often pushed well back from the roadway. Substantial terracing of the lot with
added grading and vegetation removal is required in many cases. Although the intent of these
municipal requirements is to provide privacy and spacing between units, the end result is often totally
cleared, totally graded lots, which can be visually monotonous. Configuring lots in a rectilinear shape
may optimize the number of units but municipalities should require that the site design in total should be
made to fit the land as much as possible.
Figure 5.6-1 Residential Area with Disturbance Minimized
Municipal criteria that impose road geometry are usually contained within the subdivision and land
development ordinance (SALDO), while densities, lot and yard setbacks, and minimum frontages are
usually contained in the zoning ordinance. Variations in these land development standards should be
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accepted by the local government where appropriate, which should modify their respective ordinances.
Municipalities should consider being more flexible without compromising public safety in terms of:
Road vertical alignment criteria (maximum
grade or slope).
Road horizontal alignment criteria (maximum
curvature)
Road frontage criteria (lot dimensions)
Building setback criteria (yards dimensions)
Related Non-Structural BMPs, such as road width
dimensions, parking ratios, impervious surface
reduction, chemical maintenance of newly created
landscapes, and others are discussed as separate
BMPs in this Chapter, though are all substantially
interrelated.
Figure 5.6-2 Minimally Disturbed Development
Detailed Stormwater Functions
Volume Reduction Calculations:
Minimizing Total Disturbed Area can reduce the volume of
runoff in several ways. Reducing disturbance and maintaining a natural cover can significantly
reduce the anticipated volume of runoff through increased infiltration and increased
evapotranspiration. This practice will be self-crediting in site stormwater calculations through lower
runoff coefficients and/or higher infiltration rates. Minimizing Total Disturbed Area can reduce
anticipated runoff volumes because undisturbed areas of existing vegetation allow more infiltration
to occur, especially during smaller storm events. Furthermore, employing strategies that direct non-
erosive sheet flow onto naturally vegetated areas can allow considerable infiltration to occur and
can be coupled with level spreading devices (see Chapter 6) and possibly other BMPs to more
actively manage stormwater that cannot be avoided. In other words, Minimizing Total Disturbed
Area/Maintained Area through Reduced Site Grading (Designing with the Land) not only prevents
increased stormwater generation (a volume and peak issue), but also offers an opportunity for
managing stormwater generation that cannot be avoided. See Chapter 8 for volume reduction
calculation methodologies.
Peak Rate Mitigation Calculations:
Minimizing Total Disturbed Area/Maintained Area through
Reduced Site Grading (Designing with the Land) can reduce the peak rate of runoff in several ways.
Reducing disturbance and maintaining a natural cover can significantly reduce the runoff rate. This
will be self-crediting in site stormwater calculations through lower runoff coefficients, higher
infiltration rates, and longer times of travel. Minimizing Total Disturbed Area/Maintained Area
through Reduced Site Grading (Designing with the Land) can lower discharge rates significantly by
slowing runoff and increasing on-site storage.
Water Quality Improvement:
Minimizing Total Disturbed Area can improve water quality
preventively by reducing construction phase sediment-laden runoff. Water quality benefits also by
maximizing preservation of existing vegetation at a site (e.g., meadow, woodlands) where post-
construction maintenance including application of fertilizers and pesticides/herbicides is avoided.
Given the high rates of chemical application which have been documented at newly created
maintained areas for both residential and non-residential land uses, eliminating the opportunity for
chemical application is important for water quality – perhaps the most effective management
technique. In terms of water quality mitigative functions, Minimizing Total Disturbed Area provides
filtration and infiltration opportunities, assuming that undisturbed areas are being used to manage
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stormwater generated elsewhere on the development site, as well as thermal mitigation. See
Chapter 8 for Water Quality Improvement methodologies.
Design Considerations
During the initial conceptual design phase of a land development project, the applicant’s design
engineer should provide the following information, ideally through development of a Minimum
Disturbance/Minimum Maintenance Plan:
1. Identify and Avoid Special Value/Sensitive Areas (see BMP 5.4.1)
Figure 5.6-3 Woodlands Protected through Minimum Disturbance Practices
Delineate and avoid environmentally sensitive areas (e.g., Primary and Secondary Conservation
areas, as defined in BMP 5.4.1); delineation of Woodlands, broadly defined to include areas of
immature and mixed tree growth, is especially important; configure the development program on the
balance of the parcel (i.e., Development Areas as discussed in BMP 5.4.1).
2. Minimize Disturbance at Site
Modify road alignments (grades, curvatures, etc.), lots, and building locations to minimize grading,
earthwork, overall site disturbance, as necessary to maintain safety standards. Minimal disturbance
design shall allow the layout to best fit the land form without significant earthwork. The limit of
grading and disturbance should be designated on the plan documentation submitted to the
municipality for review/approval, and should be physically designated at the site during construction
by flagging, fencing, or other methods.
3. Minimize Disturbance at Lot
Limit lot grading to roadways and building footprints. Municipalities should establish Minimum
Disturbance/Minimum Maintenance Buffers, designed to be rigorous but reasonable in terms of
current feasible site construction practices. These standards may need to vary with the type of
development being proposed and the context of that development (the required disturbance zone
around a low density single-family home can be expected to be less than disturbance necessary for
a large commercial structure), given the necessity for use of different types of construction
equipment and the realities of different site conditions. For example, the U.S. Green Building
Council’s Leadership in Energy & Environmental Design Reference Guide (Version 2.0 June 2001)
specifies the following:
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…limit site disturbance including earthwork and clearing of vegetation to
40 feet
beyond
the building perimeter,
5 feet
beyond the primary roadway curbs, walkways, and main utility
branch trenches, and
25 feet
beyond pervious paving areas that require additional staging
areas in order to limit compaction in the paved area…”
Municipalities in New Jersey’s Pinelands Preservation Zone for years have supported ordinances
where limits are more restrictive than the LEED footages (e.g., clearing around single-family homes
is reduced to 25 feet). Again, such requirements can be made to be flexible with special site factors
and conditions. The limit of grading and disturbance should be designated on the plan
documentation submitted to the municipality for review/approval, and should be physically
designated at the lot during construction by flagging, fencing or other marking techniques.
Figure 5.6-4 Convential Development Versus Low Impact Development
4. Maximize Soil Restoration
Where construction activity does require grading and filling and where compaction of soil can be
expected, this disturbance should be limited. Soil treatments/amendments should be considered
for such disturbed areas to restore permeability. If the bulk density is not reduced following fill,
these areas will be considered semi-impervious after development and runoff volumes calculated
accordingly.
5. Minimize Construction Traffic Areas
Areas where temporary construction traffic is allowed should be clearly delineated and limited.
These areas should be restored as pervious areas following development through a required soil
restoration program.
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6. Minimize Stockpiling and Storage Areas
All areas used for materials storage during construction should be clearly delineated with the
surface maintained, and subject to a soil restoration program following development. For low-
density developments, the common practice of topsoil stripping might be unnecessary and should
be minimized, if not avoided.
Construction Issues
Most of the measures discussed above are part of the initial concept site plan and site design process.
Only those measures that restore disturbed site soils are related to the construction and post-
construction phase, and may be considered as avoidance of impacts.
Cost Issues
Cost avoidance as a result of reduced grading and earthwork should benefit the developer. This BMP
is considered to be self-crediting, given the benefits resulting from reduced costs. Cost issues include
reduced grading and related earthwork (see Site Clearing and Strip Topsoil and Stockpile below), as
well as reduced costs involved with site preparation, fine grading, and stabilization.
Calculation of reduced costs is difficult due to the extreme variation in site factors that will affect costs
(amount of grading, cutting/filling, haul distances for required trucking, and so forth). Some relevant
costs factors are as follows (as based on R.S. Means,
Site Work & Landscape Cost Data
, 2002):
Site Clearing
Cut & chip light trees to 6” diameter
$2,900/acre
Grub stumps and remove
$1,400/acre
Cut & chip light trees to 24” diameter
$9,700/acre
Grub stumps and remove
$5,600/acre
Strip Topsoil and Stockpile
Ranges from $0.52 to $1.78 / cy because of Dozer horse power, and ranges from ideal to
adverse conditions
Assuming 8” of topsoil, the price per sq. yd. is $0.12 – $0.40
Assuming 8” of topsoil, the price per acre is $560 – $1,936
Site Preparation, Fine Grading, Seeding
Fine grading w/ seeding $2.33 /sq. yd.
Fine grading w/ seeding $11,277 /acre
In sum, total costs appear to approximate $20,000 per acre and could certainly exceed that figure in
more challenging sites. Reducing graded and disturbed acreage clearly translates into substantial cost
reductions.
Stormwater Management Calculations
No calculations are applicable for this BMP.
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Specifications
The modification of road geometry is a site-specific issue, but in general any criteria that will result in
significant earthwork should be reconsidered and evaluated.
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