230D97001
QUANTIFYING THE IMPACTS
OF ROAD CONSTRUCTION
ON WETLANDS LOSS
APOGEE
DRAFT FINAL REPORT
Apogee Research he 4350 East West Highway S;xt1 Floor Be:t>es3a. Maryland 2C8U 30V 652. 8W4 fax 301. 654 9355
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APOGEE
QUANTIFYING THE IMPACTS OF ROAD CONSTRUCTION
ON WETLANDS LOSS
DRAFT FINAL REPORT
PREPARED BY:
OFFICE OF POLICY, PLANNING, AND EVALUATION, UNITED STATES
ENVIRONMENTAL PROTECTION AGENCY
AND:
APOGEE RESEARCH, INC.
4350 East West Highway, 6th Floor
Bethesda, MD 20814
CONTRACT NO. 68-W4-0041
March 14, 1997
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QUANTIFYING THE IMPACTS OF ROAD CONSTRUCTION ON
WETLANDS Loss: PRELIMINARY ANALYSIS
1. INTRODUCTION
The U.S. Department of Interior's national study of the impact of federal programs on wetlands
reported that, after agricultural programs and multi-purpose water projects, the Federal Aid
Highway Program was the most frequently identified federal program source of wetland loss in
the areas studied nationally.1 The Federal Aid road system has led to wetland loss and
degradation both directly and indirectly. Road construction in and across wetlands has led to
direct and indirect wetland loss through the effects of filling, fragmentation, and alteration of
hydrology. Constructed highways have also indirectly led to wetland loss by enabling or
inducing secondary development. Further, the roadside ditches in highway rights-of-way have
been shown to provide easy drainage outlets for agricultural wetlands conversions in the Upper
Midwest and the Southeast.
While the available literature provides much anecdotal and qualitative evidence of the impacts
of the Federal-Aid Highway Program (FAHP) on wetlands loss and degradation, it appears to
provide very little in the way of empirical data on these impacts. Our review of the literature
and consultations with wetlands experts around the country did identify a few studies which
relied on aerial photography to identify wetland losses linked to road construction in specific
regions. However, no quantification of the extent of national wetland loss linked to the FAHP
has been undertaken. This is not surprising given that a rigorous empirical analysis would
likely require extensive mapping and analysis of historical Federal Aid road construction and
wetland stock and loss trends for individual states or regions. Such an effort would require
extensive data gathering and intensive analytical methods.
This paper makes a more modest and preliminary attempt to quantify the impacts of the FAHP
on wetlands loss. The analysis combines readily available data on the extent of Federal Aid
road construction and wetland loss over the life of the program with certain assumptions to
derive a rough national estimate of the potential magnitude of wetland loss resulting from the
FAHP. ft also uses the results of the few empirical studies identified in the literature to
calculate rough estimates of FAHP related wetland losses for specific regions which are used to
augment and provide perspective for the evaluation of the national estimates.
1 U.S. Department of Interior. 1988 and 1994. The Impact of Federal Programs on Wetlands. Volumes 1
and It. Areas studied in the report include the Mississippi Delta region, the Prairie Pothole Region,
southeastern Alaska, California's Central Valley, Florida's Everglades, Coastal Louisiana, Maryland's
Eastern Shore, Coastal Michigan, Northern Michigan, the Pocosins in North Carolina, New Jersey,
Puerto Rican Mangroves, the Texas Coast, and riparian areas in Idaho, Nevada, and New Mexico.
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This paper concludes that between about 310,000 and 570,000 acres of wetlands could
potentially have been lost due to the construction of FAHP roads between 1955 and 1980, at a
cost to replace of between $153 million and $6 billion. The wetland acreages represent rough
estimates and the cost figures represent orders-of-magnitude estimates. The magnitudes of
these numbers depend on the assumptions used in this analysis. Our assumptions are discussed
explicitly throughout this report.
The paper is organized as follows. The quantitative analysis of the direct and indirect effects of
Federal Aid roads on wetlands is described in Section 2. The results of this analysis are then
summarized arid evaluated in Section 3. Section 4 combines the results of the impact analysis
with various estimates of per acre wetland restoration costs to illustrate the potential costs of a
program to replace wetlands impacted by the FAHP. Two appendices and several attached
exhibits provide more detail on the roadway and wetland data used in the analysis.
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2. EFFECTS OF FEDERAL AID ROADS ON WETLANDS
2.1 DIRECT EFFECTS
2.1.1 National estimates
Four analytical steps, which relied on several key data sources and assumptions, were used to
derive national estimates of FAHP-related wetlands loss. First, the time period over which
FAHP spending was likely to have had the most significant impact on wetlands was identified.
Second, the amount of land area absorbed by Federal Aid roadway and associated rights-of-
way constructed during this period was calculated. Third, estimates for national wetland stock
and net loss over the relevant time period were identified. Finally, the results of the first three
steps were combined with certain assumptions about the probability that Federal Aid road
construction would intersect with wetlands. The methods and results of these steps are
discussed in turn below.
The FAHP has been in existence throughout most of this century. However, the bulk of FAHP
spending began in the mid-1950's with the push to construct the interstate highway system.
Thus, the year 1955 was chosen as the base year for analysis. The year 1980 was chosen as the
end year under the assumption that, by that date, wetlands protection and compensatory
mitigation requirements pursuant to NEPA, CWA Section 404 regulations, and state and local
regulatory programs had substantially reduced net wetland losses associated with Federal Aid
roads.
Estimating the total land area affected by the FAHP between 1955 and 1980 requires
calculating: 1) the total land area affected by new road miles built with FAHP funds over the
period, and 2) total land area affected by the widening of Federal Aid roads that were already in
existence as of 1955. For the first part of this calculation, data on the stock of Federal Aid road
mileage for years 1955 and 1980 were gathered and used to calculate the land area covered by
Federal Aid roadway rights-of way (ROW) built over the period 1955-80.
It should be noted that the change in FAHP road miles over the period 1955-1980 may not
exactly reflect new road construction during the study period. As a result, this analysis may
overestimate somewhat the wetlands interception rate. This is because some fraction of roads
added to the FAHP during the study period may simply have been pre-existing roads whose
status was re-defined, as opposed to entirely new roads that generated wetland impacts. Data on
the proportion of new FAHP roads that were constructed versus incorporated into the system
are not easily available and, in our opinion, would not affect the order-of-magnitude of the
impacts Apogee has estimated through this analysis.
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This analysis also used certain "rules of thumb" for total ROW width for Federal Aid roadway
in 1980.2 However, these rules of thumb may not be realistic for Federal Aid roadway miles
existing in the year 1955. Many of the Federal Aid roads in existence at that time were two-
lane roads that were subsequently widened using Federal Aid funds. To the extent that this
widening required increased ROW, then the total land area affected by Federal Aid road
construction over the period would include: 1) land area affected by increased ROW for
existing roads, and 2) land area affected by the construction of new road miles and ROW.
To account for this, estimates of the land area absorbed by Federal Aid road construction over
the period 1955-80 were calculated for two scenarios. The first assumes that ROW for 1955
roadway miles did not increase between 1955 and 1980; the second assumes that ROW for
1955 roads increased by one-third over the period. Under the first scenario, an estimated 3.184
million acres of land were covered by Federal Aid road construction between 1955 and 1980.
Under the second scenario, an estimated 7.725 million acres were covered by Federal Aid road
construction over the period. The derivation of these estimates is provided in Appendix 1.
Wetland stock and loss estimates for the period were then assembled (see Appendix 2). Only
the wetland stock estimate for year 1955 was used in the analysis described below; the net loss
estimates over the period are used in Section 3 to provide perspective for the estimates
calculated for FAHP-related wetland loss.
Finally, to derive estimates of the direct wetland impacts of Federal Aid road construction from
1955 to 1980, the data generated in the steps described above were used together with one key
assumption: that Federal Aid road construction over the period was randomly correlated with
wetland locations. The derivation of estimates for the direct impacts associated with ROW
Scenario 1 (no increase in ROW for Federal Aid road miles existing as of 1955) and ROW
Scenario 2 (increase in ROW by one-third for 1955 roadway miles) are described below.
Under Scenario 1, an estimated 3.184 million land acres were absorbed by Federal Aid road
construction between 1955 and 1980 (see Appendix 1). Assuming 3.184 million acres of
roadway placed randomly within the 1,996.83 million acre land area of the continental US, the
probability of any acre of (and being covered by roadway would be 0.16 percent. Given an
estimated 115.1 million acres of wetlands in the continental US in 1955 (see Appendix 2), the
probability of any of the 1,996.83 million land acres in the continental US being a wetland is
5.76 percent. If road placement and wetland locations were independent, the probability of
coincidence between a road and a wetland would be 0.00009216 (0.0016*0.0576). Scaling this
probability to the continental US land area yields an estimate of 184,027 total acres of wetlands
directly impacted by road construction in thecontinental US (0.000092*1,996.83 million).
2 These were supplied by staff in the Federal Highway Administration's Office of Rights of Way.
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Note that assuming a random wetlands interception rate for FAHP roads probably yields an
underestimate of the number of wetlands affected by FAHP road construction. This is because
there are substantial portions of the continental US that are sparsely inhabited and largely
devoid of wetlands. These include large tracts of land in the Rockies and the Southwest.
Subtracting these regions from the overall calculation would likely result in a roughly similar
numerator (FAHP road miles) and a considerably smaller denominator (acres of wetlands) in
the intercept rate calculation. Removing these land areas from our calculations would yield a
higher intercept rate for approximately the same national wetlands inventory, and thus a larger
estimate of affected wetlands.
It is also important to note that additional research could potentially help to refine the random-
interception assumption. It is possible, for example, that during the 1955-1980 timeframe
highway engineers either preferentially selected or avoided wetland locations for highway
construction. Reasons to select wetlands preferentially might relate to lower land acquisition
costs and fewer eminent domain issues in wetland areas; reasons to avoid wetlands might relate
to higher costs of construction in wetland areas.
Under scenario 2, an estimated 7.725 million land acres were absorbed by Federal Aid road
construction between 1955 and 1980 (see Appendix 1). Assuming these roads were located
randomly within the continental US, the probability of an acre of land being covered by
roadway would be 0.39 percent. Given that in 1955 the probability of an acre being a wetland is
5.76 percent, the probability of coincidence between a road and a wetland would be
0.00022464 (0.0039*0.0576). Multiplying this probability by the land area in the lower 48
states yields an estimated 448,567 acres of wetlands directly impacted by road construction
(0.00022464*1,996.83 million).
2.1.2 Regional Estimates
The U.S. Department of Interior's (DOI) report on the effects of Federal programs on wetlands"
discussed the results of a 1986 DOI study which attempted to empirically estimate the impacts
of Federal Aid roadways on wetlands in the Prairie Pothole region.4 That study used aerial
survey and analysis to sample 2,200 miles of Federal Aid roadways in the Prairie region. The
study found that cumulatively, at least 49,000 wetland acres had been drained in conjunction
with Federal Aid roadways in the sample survey area, and that 44 percent of these losses
(21,560 acres) resulted from the direct effects of road construction. The DOI report further
noted that "Preliminary analysis by the Service suggests that the total wetland loss in the
Prairie Pothole Region associated with federally aided roadways is at least 4-5 times greater
than the estimated loss in the sample region." Taking this estimate at face value, this suggests
that approximately 100,000 acres (4.5 times 21,560) of wetlands were lost due to the direct
impacts of Federal Aid road construction in the Prairie Pothole region.
3 U.S. Department of Interior (1988), supra note 1, page 91.
4 David Nomsen, et al. undated. Wetlands Drainage in Association with Federal Highway Projects in the
Prairie Pothole Region. As discussed in U.S. Department of Interior (1988), supra note 2.
The prairie pothole region includes roughly the western half of Minnesota, the eastern half of South
Dakota, all of North Dakota except the southeast corner, and the top third of Montana extending from
North Dakota to the Rockies. The region includes approximately 38,400,000 acres (60,000 sq. mi.), or
about 1.9 percent of the continental U.S. land mass.
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Another study provides much more limited and less useful evidence on road building in
regional wetlands during the period 1970-1980.5 That study used a sub-sample of paired data
points gathered from aerial photography in the Land Use/Cover Change Program of the U.S.
Department of Agriculture (USDA) to analyze wetland changes in fast- and medium-growth
(i.e. urban growth) counties over the period. The wetlands analysis examined aerial
photography of a total 133 paired random sample points from the USDA database, plus an
additional 86 wetland non-change points for evidence of nearby wetland change. The final
wetland change sample totaled 109 points in 14 states. Although the study included sample
points throughout the U.S., 70 percent of the final wetland change points were in the Southeast.
The study fourid that about 3 percent of the wetlands change points during the period resulted
from wetland conversions to a class of land use labeled transportation/utility, which was
defined to include roads and associated rights-of-way, other transportation infrastructure (e.g.
airports), as well as corridors for communications and utility lines.
A number of problems seriously limit the usefulness of the study results for drawing
conclusions about the effects of road building on wetlands. First, the very small number of
sample points suggests that conclusions about wetland change trends, even in the Southeast
region where most of the sample points were concentrated, would not be statistically reliable.
Second, the study reports the percentage of wetland sample points that changed status over the
period, but provides no indication of the amount of wetland land area converted. Third, the land
use category for roads also includes other transportation infrastructure as well as utility
corridors. Finally, this land use category covers all roadways, not just Federal Aid roads.
Despite these serious problems, the study results are used below to derive a very rough estimate
of wetland loss in the Southeast during the 1970's due to Federal Aid road construction. This
calculation requires several assumptions. First, the study assumes that 3 percent of the wetland
sample points that changed status to the transportation/utility land use category during the
I970's was due to conversions to roadways. Second, it assumes that, since Federal Aid
roadways comprise only about 25 percent of all roadways, only 0.75 percent (0.03*0.25) of the
change in wetland status in the Southeast over the period can be attributed to Federal Aid road
construction. This estimate is then combined with data from the Fish and Wildlife Service
(FWS) on wetland loss in the Southeast from 1974-1983, the closest comparable time period
for which data are available. That source reports that net wetland loss in the Southeast during
this period was 2.331 million acres (89 percent of the national total). Multiplying this estimate
by 0.75 percent yields an estimate of 17,482 wetland acres lost in the Southeast as a result of
Federal Aid road construction during the 1970's.
5 Earth Satellite Corporation. 1988. Wetlands Loss in Rapid Growth Counties: Analysis of Remote
Sensing Data. Report prepared for the U.S. Environmental Protection Agency, Office of Policy Analysis-
Water Economics Branch. (September).
6 J.M. Heftier et al. 1994. Southeast Wetlands: Status and Trends. Mid-1970 's to Mid-!980's. U.S.
Department of Interior, Fish and Wildlife Service.
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U.S. EPA Headquarters Library
2.2 INDIRECT EFFECTS OF ROADS Mail code 3201
1200 Pennsylvania Avenue NW
2.2.1 Induced Agricultural Drainage Washington DC 20460
The U.S. Department of Interior's (DOI) analysis of the effect of federal programs on wetlands
noted that the roadside ditches associated with Federal Aid roadway rights-of-way provide a
ready outlet for draining nearby wetlands for agriculture, particularly in the Prairie Pothole
region. The 1986 aerial survey and analysis of the impacts of Federal Aid roads on wetlands in
the Prairie Pothole region described in the previous section8 concluded that, of the estimated
49,000 acres of wetland loss linked to Federal Aid roadways, 56 percent of this loss (27,440
acres) resulted from agricultural drainage facilitated by ready access to roadway ditches.
Again, taking at face value DOI's conclusion that the total wetland loss in the Prairie Pothole
region associated with Federal Aid roadways was at least 4-5 times greater than the estimated
loss in the sample region, this suggests that approximately 123,000 acres of wetland loss in the
Prairie Pothole region resulted from agricultural wetland drainage into Federal Aid roadway
rights-of-way.
2.2.2 Other Indirect Impacts
In addition to induced wetland drainage for agriculture, Federal Aid roadways have led to
wetland loss and degradation in other indirect ways. For example, when a highway bisects or
even abuts a wetland area, significant adverse effects can result from altered hydrology and
loss of contiguity. Federal Aid road construction can also indirectly impact wetlands by
inducing or enabling secondary development. The construction of additional road capacity, by
increasing travel opportunities and reducing travel cost, could spur additional residential and
commercial development or cause development to be more dispersed (i.e. development
sprawl), thus covering more total land acreage, including wetlands. While these types of effects
are no doubt real, we did not locate any data that would support even a rough quantitative
estimate of their possible magnitude.
3. SUMMARY AND DISCUSSION OF RESULTS
The key results of the preceding analysis are summarized in Table 3.1. The table includes the
estimates derived for direct wetland loss associated with the two ROW scenarios as wel! as the
estimate of indirect wetland loss derived for the Prairie Pothole region. The estimates of direct
wetland loss for the Prairie and Southeast regions are not included in the table. The latter is
excluded because it is unreliable. The former, while not included in the table, is used below to
lend perspective for evaluating the national estimates of direct wetland loss.
In the table, each of the ROW scenario estimates of direct wetland loss for the nation are
summed with the estimate of indirect wetland loss for the Prairie Pothole region to produce an
estimated range for total wetland losses attributable to Federal Aid road construction over the
period 1955-80. Since the direct loss estimates comprise the bulk of the total loss estimates,
these are reviewed and evaluated further below.
U.S. Department of Interior (1988), supra note 3.
Nomsen, et al (undated), supra note 4.
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TABLE 3.1 WETLAND LOSSES POTENTIALLY ATTRIBUTABLE
TO FEDERAL AID ROADS SINCE 1955
TYPE OF IMPACT
Direct: road construction
Indirect: induced drainage
for agriculture
Induced agricultural
drainage in other regions
and other indirect effects
Total (direct + indirect)
WETLAND ACRES LOST
184,027 acres
448,567 acres
123,000 acres
NA
307,027 to 57 1,567 acres
BASIS FOR ESTIMATE
Random correlation national
estimate: ROW scenario 1
Random correlation national
estimate: ROW scenario 2
Prairie region only
No basis for quantitative
estimate
Direct (ROW scenario I ) plus
indirect - Direct (ROW
scenario 2) plus indirect
The two estimates of direct wetland loss for the nation (184,027 and 448,567 acres,
respectively) differ only because of the different assumptions used in their calculation
regarding the widening of the stock of Federal Aid roads and associated rights-of-way over the
period 1955-1980. Both national estimates are based on the random correlation assumption
which likely understates the actual impact of Federal Aid roadways on wetlands given that a
large share of federal Aid roadways were built in the Eastern U.S. which also accounts for the
bulk of historical and current US wetlands. Application of the random correlation assumption
for individual regions would probably produce, when aggregated to the national level, a higher
estimate of Federal Aid road impacts on wetlands than that produced by applying the random
correlation assumption to the nation as a whole.
The Prairie region study discussed in Section 2.1.2 provides the only reliable estimate of direct
wetland loss associated with Federal Aid roads identified for this study. Accordingly, the study
estimate of 100,000 wetland acres lost in that region due to the direct effects of Federal Aid
road construction lends valuable perspective for evaluating the national estimates of direct
wetland loss derived in this paper. The Prairie Pothole region, which includes parts of
Montana, North Dakota, South Dakota, Iowa and Minnesota accounts for only two percent of
the total land area in the continental US. The region once contained about nine percent, and
now accounts for about seven percent, of the current wetland stock of the continental US.
Comparison of the 100,000 acre estimate of direct wetland loss for that one region with the
direct loss estimates for the nation suggests that the national estimates are well within the realm
of reason.
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Further perspective is provided by comparing the direct loss estimates with estimates for total
wetland loss over the period 1955-1983 (see Appendix 2). For this comparison, only the sum of
wetland losses attributable to urban and other development are applicable. The urban category
includes wetland loss due to wetland conversion in heavily urbanized areas, while the "other"
category includes all wetland loss not attributable to urban or agricultural development.9 Using
these wetland loss estimates, the national estimates of direct wetland loss associated with
Federal Aid roadway provided in the table represent 6.3 percent (ROW scenario I) and
15.0 percent (ROW scenario 2) of total wetland loss over the period not accounted for by-
agricultural conversions. Again, these percentages suggest that the estimates of direct wetland
loss for the nation attributable to Federal Aid roads may not be unreasonable.
4. ESTIMATES OF WETLAND REPLACEMENT COSTS
This section takes the estimates of wetland loss attributable to Federal Aid roads developed in
Section 1, and combines them with different wetland restoration scenarios and their associated
unit costs as developed below. This provides estimates of the potential cost of a hypothetical
wetlands restoration program intended to compensate for wetland losses resulting from Federal
Aid roads. Again, these estimates are based on hypothetical restoration programs and do not
necessarily represent the type of wetlands that will actually be restored or an opinion of what
types of wetlands restoration programs should seek to restore.
This analysis relies on the median per acre estimates of wetland restoration costs for the
wetland types presented in Exhibit 1. Median rather than average cost estimates are used since
the average cost estimates provided by Exhibit 3 are skewed upwards by sample points
reflecting extremely high per acre restoration costs for each wetland type listed. It should also
be noted that the cost data are based on small sample sizes, and are thus uncertain.
4.1 UNIT RESTORATION COST ESTIMATES
A number of possible per acre replacement cost estimates can be calculated based on a variety
of assumptions about the types of wetlands which might be the focus of a wetland replacement
program. Four different replacement scenarios and their associated per acre costs are developed
below.
It should be noted that the following replacement scenarios are meant to illustrate the potential
range of costs associated with the replacement of wetlands lost due to federal aid highway
projects. The breadth of the range estimated reflects the fact that replacement costs vary greatly
depending on the type of wetland to be replaced. These costs can range from a low of $100 per
acre for restoring agricultural wetlands to as much as $50,000 to $80,000 per acre for
mitigation projects in more urban contexts. An accurate assessment of replacement costs
would require much more detailed information on the nature of the wetlands impacts.
9 Personal communication with Thomas Dahl of the U.S. Fish and Wildlife Service.
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Scenario 1. Replacement program focus: 100% prior converted croplands
This scenario assumes that a wetlands replacement program for Federal Aid road impacts
would focus exclusively on restoring former wetlands that had been converted to agricultural
uses. As shown in Exhibit 1, the median cost for restoring such prior converted croplands is
S500 per acre.
Scenario 2. Replacement program focus: 80% prior converted croplands; 20%
freshwater mixed wetlands
Given the median restoration cost estimates for these two types of wetland restorations shown
in Exhibit 1, the weighted average per acre restoration cost for this scenario is $5,080
[(0.80*$500)+(0.20*$23,400)].
Scenario 3. Replacement program focus: 70% prior converted croplands; 30%
freshwater mixed wetlands
Given the median restoration cost estimates for these two types of wetland restoration shown in
Exhibit 1, the weighted average per acre restoration cost for this scenario is $7,370
[(0.70*S500)+(0.30*$23,400)].
Scenario 4. Replacement program focus: 70% prior converted croplands; 10%
freshwater mixed wetlands; 10% freshwater emergent wetlands; 10% freshwater forested
wetlands
Given the median restoration cost estimates for these four types of wetland restoration shown
in Exhibit 1, the weighted average per acre restoration cost for this restoration scenario is
S 10,480 [(0.70*$500V(0.10*$23,400HO. 10*$35,200)+(0.10*542,700)].
4.2 SUMMARY: WETLAND REPLACEMENT PROGRAM COSTS
The unit cost estimates derived above can be coupled with the estimates of wetland loss
attributable to Federal Aid roads (summarized in Tabie 3,1) to derive estimates for the cost of a
hypothetical wetland replacement program. These estimates of replacement costs for the four
program scenarios are provided in Table 4.1 below.
Table 4.1 Possible Wetland Replacement Program Costs
FAHP Wetland Impacts*
307,027 to 57 1,567 acres
307,027 to 57 1,567 acres
307,027 to 57 1,567 acres
307,027 to 57 1, 567 acres
Unit Replacement Cost
$500 per acre
$5,080 per acre
$7,370 per acre
$10,480 per acre
Total Replacement Cost
$153 to $285 million
$1,5 59 to $2,903 million
$2,262 to $4,2 12 million
$3,217 to $5,990 million
* Estimates taken from Table 3.1
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Appendix 1
FEDERAL AID ROAD MILEAGE AND LAND AREA
The analysis outlined below was used to estimate the total acreage directly impacted by Federal
Aid road construction during the period in which Federal Aid spending likely had the greatest
impact on wetlands loss. The analysis includes three steps. First, the cumulative acreage
affected by Federal Aid roads as of year 1980 was calculated. The 1980 cutoff date is used
under the assumption that by that year wetland protections had eliminated net wetland impacts
associated with Federal Aid road construction. Second, the total land area affected by Federal
Aid roads as of the year 1955 was calculated for two different scenarios for assumed rights-of-
way (ROW): 1) Federal Aid road miles as of 1955 had ROW area of 150 feet, 2) Federal Aid
road miles in 1955 had ROW area of 100 feet. Third, the estimated land area for Federal Aid
roads existing as of 1955 under the two different ROW scenarios were subtracted from the land
area estimate for year 1980 to isolate the effect of Federal Aid road construction between 1955
and 1980. These analytical steps are described in detail below.
Step 1. Estimate total land area covered by Federal Aid roads as of year 1980
1. Total U.S. public road and street mileage broken down by rural, urban, and functional
system was reported for 1980.10
2. Total road mileage for Alaska and Hawaii was subtracted out.
3. Rural interstate, rural non-interstate, urban interstate, urban non-interstate and total Federal
Aid highway road mileage was computed for the continental U.S. (lower 48 states). Rural
Federal Aid highways include: interstates. principal arterials, minor arterials, and major
collectors. Federal Aid highway funding may not be used for rural minor collectors and
local roads. Urban Federal Aid highways include: interstates, freeways and expressways,
principal arterials, minor arterials, and collectors. Federal Aid highway funding may not be
used for urban local roads.
4. Right-of-way width varies significantly based on functional system classification as well as
on less predictable factors such as cost and availability of land. However, rule of thumb
estimates provided by FHWA's Office of Right-of-Way were used in these calculations.
This analysis assumed a 300 foot right-of-way for rural interstates, and a 150 foot right-of-
way for urban interstates as well as both rural and urban non-interstate Federal Aid roads.
5. For each functional system classification, highway mileage was multiplied by 5280
(representing the number of feet in a mile) to estimate total length in feet. This estimate
was then multiplied by right-of-way area (300 or 150 feet) to estimate total area in square
feet. Finally, this estimate was divided by 43,560, the number of square feet in an acre (see
table below).
10 United States Department of Transportation. FHWA, Highway Statistics ]98Q. page 114.
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1980 Continental U.S.
Federal Aid Rural/Urban
Mileage
Rural Interstate Federal
Aid Mileage
Rural Non-Interstate Federal
Aid Mileage
Urban Interstate Federal Aid
Mileage
Urban Federal Non-Interstate
Aid Mileage
Total Rural and Urban
Federal Aid Mileage
Highway
Mileage
31,997
662,918
9.184
185,087
892,303
Estimated
Right of
Way (Feet)
300
150
150
150
*
Acreage Lost
as of 1980
1,163,527
12,109,727
166,982
3,365,218
16,805,455
Step 2. Estimate land area covered by Federal Aid roads existing as of 1955
1. Total U.S. Federal Aid road mileage of 749,166 was reported for 1955.'1 (Note: data on
road miles broken down by state, urban and rural, and functional system are not available
for this year).
2. For the 150 foot ROW scenario, the estimate of total Federal Aid road mileage for 1955
was multiplied by 5280 (the number of feet in a mile) to calculate total road length in feet.
This estimate was then multiplied by an assumed 150 foot ROW to calculate total area in
square feet. This estimate was then divided by 43,560 (the number of square feet in an
acre) to estimate a total land area in acres of 13,621.200 million.
3. For the 100 foot ROW scenario, the estimate of total Federal Aid road mileage for 1955
was multiplied by 5280 to calculate total road length in feet. This estimate was then
multiplied by an assumed 100 foot ROW to calculate total area in square feet. This
estimate was then divided by 43,560 to estimate total land area in acres of 9,080,080
million.
Step 3. Isolate Federal Aid land area covered between 1955 and 1980
1. The estimate of land area covered by Federal Aid road in 1955 for the 150 foot ROW
scenario (13.621 million acres) was subtracted from the estimate of land area for Federal
Aid road in 1980 (16,805 million acres), resulting in an estimated 3.184 million acres
covered by Federal Aid roads and rights-of-way between 1955 and 1980.
U.S. Department of Transportation, FHWA. Highway Statistics Summary tQ
Quantifying the Impacts of Road
Construction on Wetlands Loss
12
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Apogee Research, Inc,
March 14, 1997
2. The estimate of land area covered by Federal Aid road in 1955 for the 100 foot ROW
scenario (9.080 million acres) was subtracted from the estimate of land area for Federal
Aid road in 1980 (16.805 million acres), resulting in an estimated 7.725 million acres
covered by Federal Aid roads and rights-of-way between 1955 and 1980.
Appendix 2
WETLAND STOCK AND NET LOSS ESTIMATES FOR THE CONTERMINOUS U.S.
(In millions of acres)
YEAR/
TIME
PERIOD
1955
1955-1974
1974
1974-1983
1983
1983-1992
TOTALS
WETLAND
STOCK
115.1
105.9
103.3
TOTAL
NET LOSS
9.15
2.61
0.79
12.55
NET LOSS
FROM
AGR. DEV.
6.91
1.38
0.16
8.45
NET LOSS
FROM
URBAN
DEV.
1.09
0.12
NA
1.21
NET LOSS
FROM
OTHER
DEV.
0.69
1.03
0.45
2.17
Sources:
1. The U.S. FWS 1982 National Wetlands Inventory (1982 NWI). As reported by: W.E.
Frayer, et al. 1983. Wetlands and Deep-water Habitats in the Conterminous United States,
1950's to I970's. U.S. Department of Interior, U.S. Fish and Wildlife Service. (April).
2. The USFWS 1991 National Wetlands Inventory (1991 NWI). As reported by: Thomas
Dahl, et al. 1991. Wetlands Status and Trends in the Conterminous United States Mid-
1970 's to Mid-1980 's. First Update of the National Wetlands Status Report. U.S.
Department of Interior, U.S. Fish and Wildlife Service.
3, The USDA 1992 National Resources Inventory (1992 NRI). As reported by: Ralph
HeimHch. 1995. "Wetlands Lost, Wetlands Gained". National Wetlands Newsletter. Vol.
17, No. 3. (May-June)
Explanation of Data:
• The loss estimates provided by the table represent net losses which reflect the amount of
wetlands converted to development uses less the amount of land that was classified as
developed land at the beginning of the period but reclassified as wetlands at the end of the
period. In any period, the sum of net losses attributed to agriculture, urban, and other
development is slightly lower than the total net loss for the period because some of the total
is accounted for by the conversion of wetlands to open water.
Quantifying the Impacts of Road
Construction on Wetlands Loss
13
Draft internal EPA document
Do not cite or quote
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Apogee Research, Inc. March 14, 1997
• The 1955 inventory estimate was derived from the revised estimate of wetland stock in
1974 as reported by the 1991 NWI, less the estimate of total net wetland loss over the
period 1955-1974 as reported by the 1982 NWI.
• The estimates of net losses for the period 1955-1974 were reported by the 1982 NWI. Note:
this source reports gross wetland losses resulting from agriculture, urban, and other
development, but only reports one aggregate estimate of the amount of developed land
which was reclassified as wetlands during the period. For the table, it was assumed that
formerly agricultural lands accounted for the total reported amount of developed land that
was reclassified as wetlands during the period.
• The 1974 and 1983 stock estimates, as well as the net loss estimates for the period 1974-
1983, were reported by the 1991 NWI.
• The estimates of net losses for the period 1983-1992 were reported by the 1992 NRI.
These represent conservative estimates since the NRI covers primarily rural wetlands
located on non-federal lands. Note: the NRI does not report separate loss estimates for
urban and other development as does the NWI; the estimate attributed to other
development in the table includes all development loss that is not attributed to agriculture
or similar uses (e.g. rangeiand, silviculture).
Quantifying the Impacts of Road 14 Draft internal EPA document
Construction on Wetlands Loss Do not cite or quote
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Apogee Research, Inc. March 14, 199'/
Exhibit 1
WETLAND RESTORATION COSTS
The table below provides estimates of restoration costs (which exclude land costs) for different
wetland types. The estimates were constructed based on detailed engineering and cost
accounting profiles for over 500 different wetland restoration projects. Note: the sample sizes
may limit the certainty of these estimates for nationwide use.
Wetland Restoration Cost Estimates and Cost Allocation by Task and Input Category
(excludes land cost)
Project Type
Aquatic Complex
Bed
Fresh-
water
mixed
Fresh-
water
Forest*
Fresh-
water
Emerg.
Fresh-
water
Tidal
Salt
Marsh
Man-
grove
Agric.
Conv**
Project Cost (thousands of dollars)
Average
Minimum
Maximum
Median
Sample Size
Cost Breakdown by Tasks
Preconstruction
Construction
Postconstruction
$19.5
18.3
21.7
18.6
•^
S56.7
4.3
258.8
24.8
8
S25.3
1.4
65.8
23.4
10
S77.9
0.9
248.4
42.7
19
S48.7
1.7
170.6
35.2
28
S42.0
0.6
92.6
32.9
3
$18.1
1.0
43.6
!0.2
9
SI 8.0
2.1
42.8
13.6
4
Sl.O
0.005
20.8
0.5
494
(% of total cost):
17%
63
20
Cost Breakdown by Input Category (%
Labor
Materials
Equipment
Other
58%
8
34
0
10%
74
16
of total
50%
23
14
14
5%
78
17
COSt):
74%
10
16
0
9%
74
IS
51%
30
IS
2
13%
58
28
63%
26
9
1
9%
87
4
31%
54
14
I
16%
73
11
52%
27
20
2
13%
66
21
51%
21
28
0
0%
100
0
45%
0
55
0
* High end of range involves researching and restoring hydrology and planting; low end involves
restoring hydrology only.
** Cost breakdowns for agricultural conversions are based on a project consisting of hydrologic
modification without planting or formal plan development.
Source: Dennis King and Curtis Bohlen. 1994. Making Sense of Wetland Restoration Costs.
University of Maryland, Center for Environmental and Estuarine Studies. Unpublished paper.
(January).
U.S. EPA Headquarters Library
Mail code 3201
1200 Pennsylvania Avenue NW
Washington DC 20460
Quantifying the Impacts of Road 15 Draft internal EPA document
Construction on Wetlands Loss Do not cite or quote
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Apogee Research, Inc.
March 14, 1997
250 -,
Exhibit 2. Wetland Stock (millions of acres)
221
103.3
Pre 1955
1983
Explanation of graph:
• Appendix 4 graphically depicts the aggregate wetland stock from the time of settlement'
through 1983.
12 Dahl, Thomas E. "Wetlands Losses in the United States 1780's to 1980's," U.S. Department of
Interior, U.S. Fish and Wildlife Service, 1990.
Quantifying the Impacts of Road
Construction on Wetlands Loss
16
Draft internal EPA document
Do not cite or quote
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Apogee Research, Inc.
March 14, 199:
on
8
•o
§
10
9
Exhibit 3. Net Loss Estimates for the Conterminous U.S.
: (millions of acres)
9.15 ,
o.4«. -.-. -,., ^v •'•"' :' • •' -..'
| 0.69 : -<----' ••^••-:. .••--:•••••
1955-1974
gjOpen Water
DOther
• Urban
Agriculture
1974-1983
Years
1983-1992
0.18
0.16
Explanation of graph:
• Appendix 5 graphically depicts net wetland losses during the periods 1955-1974, 1974-
1983, and 1983-1992. .
• Total net losses have been disaggregated into the following groups: agriculture, urban,
other, and open water.
Quantifying the Impacts of Road
Construction on Wetlands Loss
17
Draft internal EPA document
Do not cite or quote
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