Impacts and Mitigation - Princeton University

Chapter 6

Impacts and Mitigation

Photo credit: U.S. Fish and Wildlife Service

Contents

Page

Chapter Summary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .............. 117

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 117

Definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 118

Development Activities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....... 119Dredging and Excavation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 119Filling . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 120Drainage and Clearing . . . . . . . . . . . . . . . . . . . . . . .. .. .. ... ... ....... . . . . . 121Extensive Flooding . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 122Water Withdrawals and Diversions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123Disposal and Discharge of Pollutants and Nonpoint-Source Pollution . . . . . . . . . . . . . . . . . . 123

Variables of Wetland-Impact Magnitude . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124Physical and Chemical Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 124Biological and Ecological Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 125Operations Variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .......125

Predict ing Impacts o f Development Act iv i t ies . . . . . . . . . . . . . . . 126Limitations . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 126Wetland Reviews . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 127General Permits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 128

Mitigating Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129Feasibility of Compensation or Offsite Mitigation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 130Onsite Mitigation to Minimize Impacts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 131Management Plans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133

C h a p t e r 6 R e f e r e n c e s . . . . . . . . . . . . . . . . . . . . . . . . 1 3 5

Chapter 6

Impacts and Mitigation

CHAPTER SUMMARY

Wetlands are important to development activitiessuch as agriculture, forestry, port and harbor de-velopment, oil and gas extraction, housing and ur-ban growth, mining, and water-resource develop-ment. Development activities that involve excava-tion (or dredging), filling, clearing, draining, orflooding of wetlands generally have the most signifi-cant and permanent impacts on wetlands. Theseimpacts vary from project to project, depending onthe scale and timing of the project, the type ofwetland affected, and many other variables. Directimpacts associated with some development activitiesoften can be mitigated by redesigning the projector modifying the construction timetable.

The ability to restore significantly degraded wet-lands to their original condition depends on the typeof wetland and on the degree to which it has been

affected either by natural processesment activities. For example, San

or by develop-Francisco Bay

wetlands that were once used for agriculture arebeing restored by removing manmade dikes thatseparated these wetlands from the bay. It is alsopossible to create new wetlands in areas that arenot subject to a high degree of wave action or swiftcurrents. Costs of creating new wetlands in relative-ly calm coastal environments range from as littleas $250/acre to over $6,000/acre.

The ability to construct new wetlands should notbe used as sole justification for the unregulated con-version of wetlands to other uses: manmade wet-lands do not necessarily provide the same valuesas natural ones. In addition, it is probably not possi-ble to create new wetlands at the rate they have beenconverted to other uses in the past.

INTRODUCTION

Generally, any wetland-development activity ofa significant magnitude has the potential to affectwetlands adversely. This chapter identifies the ac-tivities and operations that affect wetlands anddescribes the nature of their impacts. The actualimpacts of an activity, however, are site and proj-ect specific. In other words, an activity with majorimpacts in one circumstance may have moderateimpacts in another. All major development activi-ties responsible for wetland loss, including thoseregulated under the 404 program, are included inthis discussion.

The present ability to predict or monitor impactson wetlands also is evaluated in this chapter. Im-pact assessment is a critical step in determiningwhat development activities to allow in wetlandsand how to mitigate potential impacts. The uncer-

tainty associated with impact assessment influencesboth the ability to safeguard wetlands and the equityof regulatory decisions. On the one hand, wetlandsrequire protection from project impacts that are notalways obvious; on the other, regulatory decisionsbased on highly uncertain impact assessments mayimpose unnecessary burdens on developers.

Finally, opportunities for and limitations ofmitigating impacts are evaluated in this chapter.Under the current regulatory program, mitigationconditions are imposed on about one-third of allpermits processed annually; in comparison, lessthan 3 percent of all applications are denied. Thissuggests that the strategyminimize or compensateprevent development.

of the 404 program is tofor impacts rather than

117

118 . Wetlands: Their Use and Regulation

DEFINITIONS

The Council on Environmental Quality (CEQ)distinguishes between three basic types of impactsin the National Environmental Policy Act (NEPA)regulations: 1

●

●

Ž

Cumulative impacts are those impacts on theenvironment that result from the incremen-tal impact of a development activity whenadded to other past, present, and reasonablyforeseeable future activities. Cumulative im-pacts can result from individually minor, butcollectively significant, activities taking placeover time.2

Direct effects are caused by specific activitiesand occur at the same time and place as theactivities. 3 *Indirect, or secondary, effects are caused bythe activities and are later in time or fartherremoved in distance but still reasonably fore-seeable. Indirect effects may include growth-inducing effects and other effects related to in-duced changes in the pattern of land use, pop-ulation density, or growth rate, and related ef-fects on air and water and other natural sys-tems, including ecosystems.4

Impacts can also be described as permanent ortemporary, and short or long term. The former dis-tinction refers to whether or not the wetland restoresitself naturally after suffering impacts; the latter in-dicates the length of time an impact takes to mani-fest itself after the activity occurs. An activity mayhave temporary and permanent impacts, as wellas short- and long-term impacts, simultaneously.

ICFR title 40, pt. 325 to end, July 1, 1982.2S. 1508.7.3S. 1508.8.“The words “effect” and ‘ ‘impact’ are used interchangeably in

both the CEQ regulations and this chapter.4S. 1508.8.

A canal dredged through a wetland area, for in-stance, will immediately damage a wetland by re-moving vegetation and wetland soil; this impact,in most cases, is permanent. The dredging, how-ever, also will cause turbidity—generally a short-term, temporary impact—and slumping of adja-cent wetland areas into the canal-potentially along-term, permanent impact.

Two other terms used to describe impacts in thischapter are onsite and offsite. Activities can impacta wetland whether they take place directly on thewetland (onsite) or some place removed from thewetland (offsite). In general, offsite activities willhave less immediate impacts than will onsite ac-tivities. Dredging in a wetland will remove vegeta-tion and overlying substrata and cause immediatedamage, Erosion of fill material disposed in areasadjacent to a wetland may cause gradual accumula-tion of sediment in the wetland over a longer time.

The term mitigation as used in the NEPA regula-tions

a)

b)

c)

d)

e)

includes:

avoiding the impact altogether by not takinga certain (i. e., activity) action or parts of anaction;minimizing impacts by limiting the degreeor magnitude of the action and its implemen-tation;rectifying the impact by repairing, rehabili-tating, or restoring the affected environment;reducing or eliminating the impact over timeby preservation and maintenance operationsduring the life of the action; andcompensating for the impact by replacing orproviding substitute resources or environ-ments.5

540 CFR, pt. 1508.20.

Ch. 6—Impacts and Mitigation ● 119

DEVELOPMENT ACTIVITIES

Dredging and Excavation

Both dredging and excavation in wetlands in-volve the direct removal of wetland vegetation andthe underlying wetland soil. Because the elevationof the dredged area is reduced, it normally will beflooded by deeper water most of the time, therebyeliminating the possibility of recolonization bywetland plants unless the area becomes subsequent-ly filled, either naturally or by man. For example,dredging or excavation are responsible for wetlandlosses associated with agricultural conversion inNebraska; mosquito-control ditching along the eastcoast in North Carolina; canal construction incoastal Louisiana, Mississippi, and Texas; peatmining in Maryland, Michigan, and Minnesota;phosphate mining in North Carolina and Florida;

the extraction of other materials such as borax,potash, soda ash, lithium, gold, sand, and gravel;and port and other water-dependent coastal devel-opment.

Dredging commonly is used to deepen orstraighten waterways for navigation, port, andmarina facilities or for flood control. In additionto the direct effects of removing wetland vegeta-tion and soil, dredging may impact wetlands evenif it takes place offsite. Giese and Mello (21), forinstance, found that dredging a navigation inlet intoa small estuary increased the tidal range in the up-per estuary, exposing the bottom at low tide. Salini-ty was increased, shellfish beds were exposed, ben-thic (i. e., bottom-dwelling) invertebrate populationswere eliminated, and vegetation patterns werechanged. The dredging of canals primarily for ac-

Photo credit: Office of Technology Assessment, Joan Ham

The dredging of canals for navigation and for access to oil and gas development sites in coastal Louisiana has led tosaltwater intrusion into freshwater marshes. The excess salinity eventually kills the marsh vegetation

120 ● Wetlands: Their Use and Regulation

cess to oil and gas development sites also has con-tributed significantly to direct and indirect wetlandlosses in coastal Louisiana (15). While many earlystudies attributed these losses to the presence oflevees on the Mississippi River, which reduced thesediments contributing to the buildup of deltas andwetlands (8), several recent studies in the Mississip-pi Delta have shown a positive correlation betweencanal density and the extent of wetland loss (13,53).In addition to direct wetland loss resulting from thedisposal of dredged material along canal banks, theincrease in canal density in an area leads to moresaltwater intrusion into wetlands as water is flushedin and out by the tides. Salinity changes may killvegetation, and tidal flows help erode the banks ofcanals, causing them to widen at the annual ratesof from 2 to 14.8 percent per year. At the high an-nual rate, a canal would double its width in only4.7 years.

Excavation commonly is used for mining and tocreate dugouts, or reuse pits, for irrigation. Min-ing for minerals such as peat, phosphate, and lime-rock will cause total removal of wetland vegetationoverlying these deposits (30). Additional adverseimpacts also may result. For example, after lime-rock was excavated and removed from the BiscayneAquifer in southern Florida, ground water filledthe pits left by the excavation, lowering the watertable. The stockpiling of materials, the construc-tion of access roads, and other filling associated withdevelopment and operation of a mine also block sur-face waterflows. Water-filled rockpits, which areattractive locations for residential development, canbecome degraded quickly by urban runoff. In ad-dition, water in the open pit is subjected to con-tinuous, year-round evaporation (9).

In another example, the number and size of wet-lands in the Rainwater Basin in Nebraska havebeen reduced through the excavation of ‘dugouts,or irrigation reuse pits. This practice results in par-tial drainage of some wetlands and the flooding ofothers (22). These wetland losses subsequently haveled to increased incidence or risk of disease to water-fowl, reduction in food supply for migratory birds,and loss of breeding and rearing habitat for birds(22).

Filling

The immediate and permanent effect of fillingis to bury wetland vegetation, increase the eleva-tion of the area, and eliminate the periodic inun-dation of the wetland (14). Several types of solidwaste are used as fill material. Municipal waste,including household refuse and incinerator residue,has been used for wetland fills. Construction anddemolition debris is used occasionally, as are stone,sand, gravel, and broken concrete from highwayconstruction. Even coal ash has been disposed ofas fill in wetlands (8), The disposal of some typesof solid waste in wetlands carries the risk of detri-mental chemical effects owing to leaching of nu-trients and toxic chemicals from the fill material.

For example, filling is a major factor associatedwith wetland loss for land-leveling and agriculturalconversion in Nebraska and California; for con-struction of impoundments in New England, theLower Mississippi River Valley, Lower ColoradoRiver Valley, South Carolina, and North Carolina;for canal construction and dredged-material dispos-al in coastal Louisiana, Mississippi, and Texas; forport, harbor, and other coastal development; forurban and industrial development in South Caro-lina, New Jersey, California, New England, southFlorida, Washington, and Alaska; for road con-struction in Alaska, New England, and Nebraska;and for disposal of waste products in Washington,California, and New England.

Filling often is associated closely with dredgingand excavation activities. For example, the majormethod used in the Southeast to create waterfrontreal estate has been to excavate canals within wet-lands, using the dredged material as fill for buildingsites. This practice not only results in complete lossof the wetland but also creates canals that are poorhabitat for both flora and fauna (26). A comparativestudy of a residential lagoon system and naturalwetlands has shown that the lagoon supports smallerfish and shellfish communities (28).

Highways built on fill material can have indirectimpacts by either flooding or dewatering adjacentwetlands. Culverts normally constructed at soil level

Ch. 6—impacts and Mitigation • 121

will prevent flooding of the road, but will not allowthe flow of subsurface water. In some instances,borrow canals adjacent to the highways also havediverted the drainage directly into a coastal estuary,permitting saltwater intrusion into the wetlandwhere the normal drainage had been cut off.

Drainage and Clearing

Narrow drainage ditches (less than 5-feet wide)may be excavated to accelerate and channel sur-face water runoff and to lower ground water levels,increasing the value of the drained land for agri-cultural and forest management. For example,draining and clearing is a major factor associatedwith wetland conversions in the prairie potholes andin Nebraska, California, the Lower MississippiRiver Valley, North and South Carolina, and southFlorida; for urban development in south Florida

and Washington; and for forestry management inNorth Carolina and the Lower Mississippi RiverValley.

The major ecological impact from draining andclearing wetlands for agricultural purposes is theloss of diverse wildlife habitat. Studies in Missouriwhere wetland channelization projects were under-taken to reduce flooding problems indicated that78 percent of bottom land hardwood forest pre-viously flooded was converted to crop productionafter project completion (19). In Louisiana, 51 per-cent of the original 4.5 million hectares of forestedwetlands have been converted to agricultural use,mostly for soybean and cotton production. The lossof hardwood forests has meant a loss of prime hab-itats for birds and mammals, as well as a loss ofcritical spawning grounds for aquatic species.Under some circumstances, ditches in agriculturalareas also may increase the runoff of pesticides, her-

.

122 • Wetlands: Their Use and Regulation

bicides, fertilizers, and animal wastes to down-stream wetland systems. The drainage may changevegetation in adjacent areas; the runoff may causepollution of adjacent land and open water areas(45). Drainage of wetlands for agricultural usesresults in the loss of organic material from the soilsdue to oxidation. In some parts of the country, thismay lead to soil subsidence and increased hazardsof fire (9). For example, reclaimed peat-based agri-cultural land in the Sacramento-San Joaquin Valleyhas subsided through processes of compaction, ox-idation, and wind loss and is now up to 20 ft belowsea level (1 7).

In some instances, the creation of new habitatshas changed the behavior of migrating birds; ricecultivation in southwest Louisiana and easternTexas has encouraged overwintering of waterfowlthat normally overwinter in eastern Louisianawetlands. Natural filling of drainage ditches maycause an area to revert to a wetland, as occurredon some former agricultural lands in New England(56).

Forested wetlands are also partially drained tolower the water table and allow harvesting of theforested land. After harvesting, an area may beallowed to regenerate naturally or replanted as apine or hardwood plantation. Active forest manage-ment can significantly increase the yield of woodfrom the land but also decrease wildlife diversitywithin forested plantations, depending on a numberof factors. Maki, et al, (31) report that the prac-tice of ‘‘high grading, ’ in which only desirablelarge and shade-intolerant species are harvested,produces extensive stands of shade-tolerant specieshaving less value as habitat. Large-scale drainageand channelization could contribute to decreasesin resident invertebrate density and diversity (3).If good management practices are not used, con-structing drainage ditches and channelizing streamsin forested wetlands may also increase erosion andsedimentation, which in turn affects wildlife habitatand water quality in adjacent areas (7). In addi-tion, the drainage of wetlands (14) may increasethe danger of floods in downstream areas.

Drainage of wetlands in south Florida has beencited as contributing to flooding, drought, oxida-tion and subsidence of peat, saltwater intrusion,reduction of fish and wildlife resources, and water-

quality problems in Lake Okeechobee-particularlyincreases in nutrients, suspended solids, and pol-lutants introduced from land uses to which wetlandsare converted (9).

Grazing of livestock in wetlands has been a com-mon practice because of the relatively rapid andlush growth of some wetland plants, particularlyin arid regions. Some wetland vegetation hasproved more nutritious for livestock than uplandforage (38). Overgrazing leads to trampling andcompaction of soft wetland soils and the loss ofnatural food sources for resident and migratorywildlife. Moderate grazing, on the other hand, canhelp maintain a wetland by encouraging the growthof annuals and by setting back vegetative succes-sion.

Other agricultural practices, such as mowing,disking, and burning wetland vegetation to con-trol crop weeds and mosquitoes, are often carriedout in the playa basins of the southern Great Plains.The adverse effects of these practices are temporaryand, like moderate grazing, can promote the growthof annual wetland vegetation (38). However, suchpractices conducted late in the growing season mayseverely curtail winter cover for upland game birdsand waterfowl.

Extensive Flooding

Permanently inundating wetlands to certaindepths will eliminate wetland vegetation. Some-times wetlands are flooded to create ponds for grow-ing aquatic organisms, particularly fish and shell-fish. Extensive flooding of wetlands is alsoassociated with agricultural conversions of prairiepotholes; development of impoundments for munic-ipal- and agricultural-water supply, hydropower,and flood control in places such as New England,the Lower Mississippi River Valley, the Lower Col-orado River Valley, Nebraska, and Alaska; water-fowl management in South Carolina; for mosquitocontrol in North Carolina; and aquiculture in Lou-isiana.

Culture ponds for crayfish and shrimp, for in-stance, are prevalent in Louisiana. These ponds areconstructed by building dikes to raise water eleva-tions. In addition to its direct effects on the wetland

Ch. 6—impacts and Mitigation ● 123

vegetation, such flooding may have indirect effectson adjacent wetlands. For example, an experimentin shrimp culture, in which a dike was built to im-pound part of a coastal wetland, led to large varia-tions in temperature and salinity with subsequentdie-offs of many organisms, including the culturedspecies (41).

The construction of dikes or the disposal of spoilfrom dredging operations may result in the im-poundment of swamps and marshes. An im-pounded swamp does not dry out periodically likea natural swamp and has a lower water turnover.This results in reduced primary and secondary pro-ductivity and decreased value for wildlife habitat.Virtually no fish are found in the stagnant waterof such an area (10).

Water Withdrawals and Diversions

Alterations in the hydrologic regime from largewater withdrawals for municipal-industrial use orlarge-scale diversions of water for irrigation andflood control can cause various impacts on wetlandecosystems. The effects of these withdrawals anddiversions on downstream wetlands are twofold,First, upstream depletions may lower the watertable in downstream freshwater wetlands, causinga temporary or permanent loss of vegetation anda decrease in habitat values. Second, decreasingfreshwater inflow in coastal areas will allow tidalincursion of saltwater into the brackish and fresh-water marshes. The increase in salinity to thesemarshes will reduce species diversity and abun-dance as well as overall ecosystem productivity.Water diversions and withdrawals also reduce theinput of detritus into the estuarine food chain.

Water diverted for irrigation and then returnedto the wetland can increase salinities and temper-atures considerably. For example, salinity in SuisunMarsh, which represents the largest contiguous wet-land area in California and 10 percent of the totalState wetland acreage, has been increasing alongwith increasing water diversions by the State andFederal water projects in the Central Valley andthe Sierras. One result has been a decline in cer-tain high-food-value plant species that are favoredby brackish-to-fresh soil-water conditions. Thesebrackish plant species are particularly important

to wintering ducks and geese (17). In addition, in-creases in water temperature owing to thermal ef-fluents from powerplants or from irrigation returnflows may cause a reduction in species diversity ofwetland flora or a shift to the more temperature-tolerant, blue-green algae that tend to produceeutrophic (oxygen-deprived) conditions.

Restricting or manipulating water flows withdams and reservoirs also can dewater downstreamwetlands. Any wetlands downstream that are notimmediately dewatered may be subject to reducedflushing, leading to a decrease in the amount ofnutrients reaching the wetlands. Greater than nor-mal floodflows can occur also when large reservoirreleases are sustained, possibly washing out wet-lands downstream.

Dikes and flood-control levees often are built toconvert wetlands in flood plains to dry farmland.These flood-control levees retain floodflows withina river channel, dewatering the wetlands behindthem. Levees within the floodway also tend to in-crease the velocity of storm runoff, produce anoverall loss of flood storage capacity, and increasethe chance of downstream flooding (45). Increasedflows may increase scouring and erosion. Unlikethe conversion of wetland by filling, land that isdrained behind or within dikes or levees can be re-stored to a wetland if the embankments are re-moved or breached.

Disposal and Discharge of Pollutantsand Nonpoint-Source Pollution

Wetlands have been used to purify wastewaterof nutrients and suspended solids, sometimes withadverse effects (4). Abundant nutrients in the wastemay increase the productivity and biomass of tol-erant vegetation in the wetland while more sensitivespecies disappear (58). Algal populations also mayshift in species composition, which may lead towetland eutrophication (23). If the wastewater vol-ume is large enough to raise wetland water eleva-tions, a conversion from emergent wetland to openwater can occur. Stormwater discharge also canhave adverse impacts on wetland functions and val-ues. For example, contaminants from urban runoffhave been noted to cause detrimental effects on tidal


wetlands around Hilton Head Island in South Car-olina (43).

A long-term effect of the disposal of contaminateddredge spoil in or near wetlands is the potential bio-availability of toxic chemicals such as oil and grease,pesticides, arsenic, and heavy metals, when the sed-iments are resuspended periodically (1). Althoughthe bioavailability of these contaminants general-ly is quite low, under certain conditions there maybe some long-term potential for bioaccumulation

of these harmful substances within the food chain,especially when contaminated dredged materials areexposed to the air (27).

For example, filling of wetlands by eroded soilis also a factor associated with wetland conversionsfrom forestry, agricultural, and development prac-tices in watersheds of the California coast; fromagricultural and development practices around theChesapeake Bay in Maryland; and from agricul-tural activities in the prairie potholes and Nebraska.

VARIABLES OF WETLAND-IMPACT MAGNITUDE

The actual impacts of a specified construction ordevelopment activity will vary geographically andby season of the year according to regionally orlocally distinct characteristics of the physical-chemical environment. The characteristics of bio-logical populations and habitats and of the wholewetland ecosystem also will modify the impacts. Adiscussion of these variables has been included hereto illustrate both the site-specificity of wetland-project impacts and the range of factors that mustbe understood to make realistic impact assessments,and to suggest how these variables may be manip-ulated to mitigate project impacts.

Physical and Chemical Variables

Composition of Wetland Soils

The physical characteristics of wetland soils willhave considerable influence on the severity of im-pacts produced by different activities in wetlands.Wetland bottom type is an important factor in spe-cies diversity and productivity. For example, a proj-ect that introduces large quantities of silt and claywould have a significant impact by smothering pro-ductive substrates. A wetland’s chemistry also mayinfluence the magnitude of a project’s impact. Theeffects of dredging in marine or brackish waters arelikely to be less severe than in freshwater becauseof the buffering capacity of these waters. Also, sincecold water generally has higher levels of dissolvedoxygen, the effects of activities that tend to depletethe dissolved oxygen will be greater if water tem-peratures are higher.

Hydrologic Regime and Water Dynamics

The hydrology of a wetland will affect substan-tially the magnitude of impacts from activities inwetlands. For example, wetlands that are hydro-logically isolated from ground water supplies, suchas perched bogs or playa lakes, will be more ad-versely affected by excavation or dredging than wet-lands that have sources of water besides precipita-tion. Excavation in these isolated wetlands maydamage the compact peat layer and/or clay layersthat seal the bottom of the wetland and hold waterwithin it (32).

The construction of highways on wetland fill hasdifferent impacts, depending on the particular wet-land hydrology. Culverts placed through a highwayfill may cause flooding of the upslope side anddewatering of the downslope side (44). In the Flor-ida Everglades, however, the same type of highwayfill with drainage culverts may be able to accom-modate the water that flows over the surface of thewetland.

Composition of Fill Material

The disposal of solid wastes, however, carries therisk of detrimental chemical and biological effectsdue to leaching of the fill material. The magnitudeof adverse impacts depends on the actual wastecomposition, which can vary physically and chem-ically according to geographic region, communitystandards, and seasonal variations. In general,municipal solid wastes have a high proportion ofbiodegradable animal and vegetable waste, rags,


wood, cardboard and paper products, as well as fer-rous metals. Leaching of organic matter such asgarbage and wood waste can lead to an increasedbiological oxygen demand (BOD) and reduced lev-els or large fluctuations in dissolved oxygen (DO).Such changes in water chemistry can cause stressto aquatic populations and changes in species di-versity.

Biological and Ecological Variables

Population Abundance, Diversity,and Productivity

Productivity, abundance, and diversity are im-portant factors in evaluating the potential impactsof a certain activity on a wetland. Highly diversewetland ecosystems with high overall productivitybut low abundance of many species maybe affectedheavily by activities that change the limiting fac-tors for selected species, thereby unbalancing thewhole structure (species composition) of that eco-system. A less diverse ecosystem may be impactedless by the same activities. Spartina marshes, whichalmost can be considered a monoculture, are knownto be highly resistant to changes in salinity andmight not be affected significantly by, for exam-ple, the reduction of freshwater inflows to theestuary from upstream use of water for cooling apowerplant.

Presence of Key SpeciesImportant to an Ecosystem

The severity of impact from a particular activi-ty will be greater if the adverse effects focus on akey species in the wetland ecosystem. For exam-ple, detritus-based food chains can easily be dis-rupted by activities that would lower the abundanceof snails and small crustaceans that help producedetritus by shredding the marsh grasses.

Habitat Diversity and Carrying Capacity

Fish and wildlife may require different habitatsduring their lifecycles, in each season, and even dai-ly, in order to meet their needs for food, water, cov-er, and reproduction. Wetlands offer a variety ofhabitats for a variety of species and life stages.Habitat diversity often has been assessed as an in-dication of the importance or health of a wetland.

The degree of impact on a wetland often will de-pend on which habitats are adversely affected; forexample, fish that use coastal marshes may be di-verted from their normal routes by large changesin salinity and flow (24).

Operations Variables

Frequency, Duration, and Season of Activity

The frequency, duration, and season of a devel-opment activity in or affecting a wetland will modifythe severity of impact. Frequent channel-mainte-nance dredging, for example, might limit the recov-ery of an adjacent wetland from the temporary ef-fects of sediment resuspension, especially wherethere is high exposure to wind and waves. Oil ex-ploration may have rather minor and temporaryadverse effects on waterfowl if access to wetlandsis limited during the breeding, nesting, and rear-ing season. Similarly, construction of a highwaythrough a wetland will have less impact on waterquality and wildlife if the construction is rapid andefficient, avoids the period of high spring runoff,and is carried out before or after the waterfowlbreeding season.

Location of Activity Within an Ecosystem

The location or orientation of development proj-ects within a wetland can alter the magnitude oftheir impact considerably. One example would bethe placement of highway fill in a wetland. If thecauseway fill is placed parallel to the direction ofsurface sheet flow and subsurface flow, the prob-lems of blocking wetland drainage or channelingthe flow through culverts will be minimized (44).In another example, if pipelaying in wetlands isconfined to the ‘‘push-ditch’ method and theequipment can operate on dry soil at the edge ofthe wetland, the impacts will be less than if theequipment is operated from mats in the wetland.

Distribution, Scale, and Type of Activity

The type, scale, and spatial distribution of con-struction or development in a wetland must be con-sidered in order to estimate reliably the project’simpact. Wetland filling, if confined to a single areaof marsh while leaving other areas undisturbed,may be preferable to a patchwork of fills distributed


throughout the marsh. Draining and clearing of a cropland have contributed to the decline of water-significant number of small, isolated wetlands for fowl in the Central and Mississippi flyways (35).

PREDICTING IMPACTS OF DEVELOPMENTACTIVITIES

Limitations

According to U.S. Army Corps of Engineer reg-ulations, ‘‘the decision whether to issue a permitwill be based on evaluation of the probable impact,including cumulative impacts of the proposed ac-tivity . . . .” Under the Corps’ public interestreview, the impacts of a proposed project must beweighed against its other costs and benefits to deter-mine if the project will be allowed. While there arecertain characteristic impacts associated with par-ticular activities, it is clear that the actual impactsof any project will vary with each site and projectand will depend on the time at which they are con-ducted. This suggests that in most cases similar ac-tivities or projects cannot necessarily be regulatedin a uniform way; the potential impacts of majorprojects that might generate significant impactsmust be evaluated on an individual basis.

Guidelines established for the 404 program rec-ognize the variability that exists from site to siteand project to project. The 404(b)(l) guidelines,for instance, require that the “permitting author-ity . . . shall determine in writing the potentialshort-term or long-term effects of a proposed dis-charge of dredged or fill material on the physical,chemical, or biological components of the aquaticenvironment. This includes determinations of thenature and degree of effect that a proposed dis-charge will have on the following: physical sub-strate, water circulation, fluctuation and salinity;suspended particulates/turbidity; contaminants; theaquatic ecosystem and organisms; and cumulativeand secondary effects.

Even under conditions of very careful site-specificand project-specific examination, however, the abil-ity to assess potential impacts accurately often islimited. In general, the immediate effects of an ac-tivity are easier to predict than long-term impacts;physical-chemical impacts are more predictable

than biological impacts; direct effects are more ap-parent than secondary effects; and the impacts ofeach project individually are much easier to predictthan the cumulative impact of many individualprojects. The short-term turbidity caused by dredg-ing, for instance, is predicted relatively easily andprecisely; predictions of most cumulative impactsare merely speculative. A study of the impacts ofdeepening navigational channels on fish and wild-life concluded that:

Assessing the impacts of navigational dredgingand the disposal of dredged material is a controver-sial exercise; the viewpoints and approaches areendless. Without question, dredging can devastatefish and wildlife resources; however, in the absenceof definitive information, impacts are sometimesmore imagined than real (l).

It is well recognized that the routine applicationof section 404(a) authority to issue individual per-mits for the discharge of dredged or fill materialcannot provide for the assessment of cumulative im-pacts on wetlands or other aquatic resources frommany individual projects that are evaluated sepa-rately. The Corps’ proposed general policies forevaluating permit applications makes a clear dec-laration:

Although a particular alteration of wetlands mayconstitute a minor change, the cumulative effectof numerous such piecemeal changes often resultsin a major impairment of the wetland resources. G

The separate examination of potential effects atdifferent but interrelated wetland sites cannot, byitself, account for the cumulative effects. TheCorps’ Environmental Advisory Board concludedthat:

Individual permit processing in specific regionsis costly and ineffective in addressing the cumula-tive impacts of existing and future similar permit

eFeder~ Rep”ster, VO1. 45, No. 184, PP. 629 740.


actions in the same region. There was generalagreement that without planning, the cumulativeimpact of activities associated with the regulatoryprogram could indeed lead to serious consequences.Planning required to assess cumulative impacts ofindividual actions must be done on a large scale—regional, watershed, ecosystem, etc. It was alsogenerally agreed that any analysis of cumulativeimpacts on an area must of necessity be based ona knowledge of local growth patterns and local plan-ning objectives. 7

Wetland Reviews

As noted in the Code of Federal Regulations,8

‘‘the District Engineer may undertake reviews ofparticular wetland areas . . . to assess the cumu-lative effect of activities in such areas. ” Somedistricts have conducted such inventories of wetlandresources, called ‘ ‘wetland reviews, particularlywhere there are large numbers of permit applica-tions and pressures for development. In some cases,the Corps has worked with State and local officialsto plan for future demands for development thatmight require section 404 authorization. Such ac-tivities also can help to reduce the time it takes tomake a permit decision and to reduce uncertaintyas to which areas are regulated under section 404.These efforts are described below.

Wetland reviews have been conducted for at leastsix estuaries on the west coast, one area in Alaska,and in the Atlantic City, N.J., area. Each reviewis different; however, the review of the SnohomishEstuary by the Seattle District in 1977-78 providesa good example of information that can be pre-sented to help reduce the uncertainty associatedwith the 404 process. The review’s goal was to pro-vide a comprehensive inventory of wetland habitats,a discussion of existing regulatory controls, andrecommendations for wetland protection. As partof the project, a complete inventory and mappingof land use and land cover was prepared. In addi-tion, fish and wildlife habitats and physical, cul-tural, and esthetic characteristics were mapped andevaluated.

From the data gathered, wetland areas within theestuary were designated as areas of importance,

‘U. S. Army Corps of Engineers, 29th Meeting of the EnvironmentalAdvisory Board, held Apr. 21-24, 1982, Arlington, Va.

*33 CFR 320.4(6)(3).

areas of environmental concern, and other areas.Areas of importance were those areas with uniqueresources or those which served critical functions.It was recommended that they be maintained intheir present state and that any 404 permit be ap-proved “only if the activity is clearly in the publicinterest. Areas of environmental concern weresensitive to development or change, but might haveuses that are ‘‘consistent with maintenance of theirhabitat values. ” It was recommended that “onlyuses in the public interest and compatible with thehabitat values should be approved. ” Other areaswere those in which ‘‘new development would haveminimal impacts on wetlands and other valuablehabitat types. ”

Since its completion, the Snohomish EstuaryWetland Study has been used regularly by the Seat-tle District. Within the Regulatory FunctionsBranch, use of the document has emphasized theidentification of wetlands as a means of determin-ing Corps jurisdiction under section 404. As a re-sult, the need for time-consuming site visits hasbeen reduced. It also is used in preapplication con-ferences to inform applicants of issues of concernand to suggest methods for minimizing impacts as-sociated with their proposal. In the Environmen-tal Resources Section, the analysis of wetlands val-ues has been used in preparing environmental as-sessments (EA’s) of proposed 404 permit activities.The detailed data base presented in the reviewsaved both time and effort in preparing environ-mental documentation. Furthermore, in the winterit provides data that would not be available evenon a site visit. On occasion, the review even hasbeen used as a data source for EA’s on sites in otherestuaries with similar habitats.

It should be noted that the Snohomish CountyPlanning Department also uses the study to evalu-ate substantial development permits under itsShoreline Master Program. The small county stafflacks the technical expertise to evaluate all the func-tional characteristics and potential impacts associ-ated with a particular site; the review contributesto the accuracy and consistency of their decisions.In addition, the important wetlands that were iden-tified in the study have been incorporated as “areasof special concern’ in the county comprehensiveplan (45).


General Permits

Advantages

In 1977, Congress authorized the Corps to ex-empt categories of activities ‘‘similar in nature’on a nationwide, districtwide, or statewide basisfrom case-by-case permit reviews. The Corps is re-quired to establish that activities regulated in thisway ‘‘will cause only minimal adverse environmen-tal effects when performed separately and will haveonly a minimal cumulative adverse effect on theenvironment. ” Regionwide and nationwide generalpermits provide several positive features for wetlandregulation. They provide regulatory consistency,avoid administrative delay and paperwork, and cir-cumvent possible duplication of control by otheragencies. Myhrum (34) notes that the nationwidepermit program allows the regulatory agencies tofocus limited personnel and finances on activitiesgenerating greater impacts. Twenty-five nationwidepermits for categorical activities, such as shorestabilization and minor road-crossing fills, havebeen authorized with special conditions attachedto each that must be followed in order for the per-mit to be valid. Division engineers of the Corps areauthorized, at their discretion, to modify nation-wide permits by adding regional conditions appli-cable to certain activities or geographic areas. Fur-ther, individual permits may be required if generalpermits are not adequate to protect aquatic ecosys-tems.

While section 404 authorizes general permits foractivities similar in nature, the Corps also has au-thorized two general permits on a nationwide basisfor areas rather than activities. The Corps’ justifica-tion for this goes back to its history of using generalpermits on an areawide basis, before the 1977amendments authorized general permits oficially.The Corps also argues that the areas granted gen-eral permits (isolated waters and waters above head-waiters) have not been regulated in the past and thatthe geographic scope and distribution of these wa-ters make them impossible to regulate effectivelyon a case-by-case basis. On the other hand, grant-ing a permit on an areawide basis, rather than onan activity basis, allows activities and projects to

take place on wetlands, regardless of the scope andmagnitude of their impact.

Disadvantages

Despite these advantages, Blumm (5) has ex-pressed the view: ‘‘Absent reporting requirements,the cumulative impacts of general permits remainlargely a matter of speculation. ” He cites thecriticism by the General Accounting Office (GAO)of cumulative impact assessment by the Corps ina GAO 1977 report: “It is not clear that our foun-dation of knowledge about impacts can support thepremise that activities or discharges and conditionsspecified under nationwide permits will necessari-ly ensure minimal adverse impacts, particularlyminimal cumulative adverse impacts. For exam-ple, minor road-crossing fills are permitted in non-tidal wetlands if they discharge less than 200 cubicyards below “mean” high water and do not ex-tend beyond 100 ft past the ordinary high watermark. Each such fill is required to be ‘‘part of asingle and complete project for crossing of a non-tidal waterbody . . .‘‘g However, successive ‘ ‘mi-nor’ crossings of a road over many isolated smallfreshwater wetlands in the Great Plains or separatednarrow riverine wetlands in a coastal delta cannotalways be said to involve only minimal cumulativeimpacts. While the Corps is required under sec-tion 404(e)(2) to review the status of nationwide per-mits every 5 years to determine if impacts have beenminimal, it is almost impossible to assess the im-pacts that have taken place as a result of the per-mit if reporting is absent. In light of this problemsome general permits now have reporting require-ments and additional reporting requirements arebeing considered for others.

Another difficulty with general permits is thatit is difficult for some developers and landownersto determine if they meet the conditions of the per-mit. To meet the general-permit conditions, for ex-ample, that a discharge of fill in an isolated wetlanddoes not adversely modify the critical habitat of athreatened wildlife species requires a high level of

‘Federal Rep”ster, vol. 45, No. 184, pp. 62, 776.


technical expertise. Parish and Morgan (40) discuss ly” maintained. Certain classes of activities will bethis problem: permitted if management practices are followed to

the extent “practical” and adverse effects are min-Lack of certainty is inherent in the language of imized. If the discharger incorrectly interprets any

the permit conditions. A discharge will be per- of these terms and an individual section 404 per-mitted if it consists of ‘‘suitable’ materials free mit is required, its issuance will involve the needfrom toxic materials, and the fill will be “proper- for federal environmental assessment.

MITIGATING IMPACTS

In line with the definitions used by CEQ miti-gation includes:

●

●

●

●

●

avoiding adverse impacts to wetlands alto-gether by denying a project permit;minimizing impacts by limiting the degree ormagnitude of a project;rectifying the impact by repairing, rehabili-tating, or restoring the affected environment;reducing or eliminating the impact on wet-lands by preservation and maintenance opera-tions during the life of the project; andcompensating for the wetland losses by replac-ing or providing substitute resources or envi-ronments." 10

For the purposes of the following discussion, abasic distinction can be drawn between those ac-tions taken to minimize the impacts of a project onwetlands and those actions taken to compensate fora project’s impact. Though the two may be usedin combination, the strategy to compensate is mostsuited to situations where little can be done tominimize project impacts. Typically, in such a case,the project totally eliminates the wetland and com-pensation entails either restoration of wetlands orcreation of new ones at another site. Filling andbulkheading of wetlands for real estate developmentor draining and clearing of wetlands for farmingare good examples.

Under the 404 program, adverse impacts are re-duced by conditioning individual permits or byusing “blanket conditioning” for general permits.Conditioning usually entails either onsite design re-quirements and construction and managementpractices to minimize impacts or requirements for

,OCFR, pt. 1 sO~.LO(a-e).

offsite compensation of unavoidable impacts. Likethe difficulties associated with assessing impacts,the effectiveness of mitigation measures in ameli-orating the impacts of a project sometimes can bevery uncertain or even speculative. Although theCorps strives to tailor mitigation measures to in-dividual permits, controversies may arise from re-quirements for expensive mitigation measures if thebenefits of these measures are questionable. In somecases, the expense of mitigation can reduce the prof-itability of projects to a point where they are nolonger worthwhile to pursue, and developers com-plain that the agencies sometimes use permit con-ditions as leverage to discourage projects.

Current Corps policy does not give much guid-ance on the level of mitigation appropriate in casesof great uncertainties, calling only for modificationsthat are ‘‘commensurate in scope and degree withthe impacts of concern. However, the Corps cur-rently is establishing a more specific policy: in theinterim final regulations issued July 22, 1982, theCorps indicates that it is beginning to address theproblem of uncertainty. Whether permits may re-quire mitigation of secondary impacts, for instance,‘‘will depend on whether the impact is at least prob-able, rather than speculative."11 In its May 12,1983, revisions of the 404 regulations, the Corpsproposed expanding authority of the district en-gineer to provide for either onsite or offsite miti-gation.

In the following sections, the feasibility of thesestrategies is evaluated, and opportunities for andlimitations of using them are explored.

jlFeder~ Register, vo l . 45 , No . 184, PP. 62 , 657.


Feasibility ofor Offsite

Creation

CompensationMitigation

Producing a new wetland usually involves fallingan open-water or upland ecosystem, which may,in itself, possess important values. Developing anew wetland entails providing the proper substratelevel and type, assuring chemical compatibility, andproviding erosion control during establishment ofvegetation. The complexity of these factors intro-duces considerable risk of failure; however, thehistorical record shows that creation of wetlands canbe successful, given proper site selection andpreplanning.

Marsh creation has occurred mainly in coastalwaters or along shorelines that are not exposed tolarge storm waves or the wakes of ships (20,39,60).Planting aquatic plants predates the 1940’s.Marshes of various sizes have been developed alongthe Mississippi River since the 1930’s, in Utah inthe 1930’s and 1940’s, and in Wisconsin and otherStates since the 1940’s. Although some projectsrange up to several hundred acres in size, marshcreation by means of artificial plantings tends tobe on a smaller scale (0, 1 to 10 acres) owing to highcosts for establishment.

The largest concentration of projects has occurredin brackish and saline environments along the mid-Atlantic and Southeastern coastlines. Wetlands alsohave been created successfully in New England,along the Gulf Coast, particularly in Texas (57),and along the west coast [e. g., San Francisco Bayand the Columbia River estuary (51)]. Somefreshwater marshes have been established on rivers(55), on the Great Lakes (59), in isolated ponds aspart of surface-mine reclamation (1 1), and in sew-age lagoons, to assist with wastewater treatment(16).

Restoration of Wetlands

Restoration involves taking an existing marshfrom a poor, unhealthy, or degraded state to thelevel of productivity and habitat value associatedwith undisturbed natural wetlands occurring in thevicinity. This process often can be accomplishedby changing surrounding water inflow or drainage,eliminating erosion and siltation, and reducing

pollution from adjacent areas (6,29,46). Restoredareas generally will have at least some semblanceof the natural elevations and substrate unless ero-sion or sediment deposition has been severe. Resi-dual populations of natural plants usually are pres-ent to serve as seedstock for widespread regenera-tion. However, re-creation of wetlands has occurredfrom seed remaining in the soil for decades.

Restoration, although not widely reported, hasbeen practiced in estuarine systems where dikinghas degraded coastal wetlands (33,47), in areaswhere normal sediment input or hydrologic patternshave been disrupted (48,49), and in brackish orsaline marshes that have been modified heavily byconstruction activities or exposed to different typesof pollutants (55). In some cases, freshwater wet-lands have been restored, as in the case of Florida’sextensive freshwater ecosystems (50,52). Marsh-res-toration projects tend to be small-usually 20 acresor less.

Costs of Creation and Restoration

Any successful marsh-creation or marsh-resto-ration project must involve costs for project plan-ning, site investigation, careful seasonal schedul-ing, and postproject monitoring. Total project coststypically range from $250/acre for a small, relativelysimple marsh-creation project (57) to over $6,000/acre for a marsh established for sewage treatment(16). Transport of substrate material by barge,truck, or dredge, and subsequent site preparationsusually account for the largest single cost whereverthe site requires extensively raised elevations. Inmost newly created wetlands, artificial plant propa-gation is also a necessary and significant cost,Scheduling of project operations within natural en-vironmental constraints, such as the periods oftides, plant germination time, and limits of thegrowing season can increase costs in the short termbut will contribute greatly to project success overthe long term. In general, it is far less costly torestore degraded wetlands than to create new wet-lands.

Prospects for Success

The success of efforts to create or restore wet-lands depends on many factors, including wetlandtype and location, project scope and size, materials


and methods used, and good project planning andmanagement, especially during the first two or threegrowing seasons. However, even a properly devel-oped wetland will require an extended period oftime for the functions of a natural wetland to evolve.For example, hydrological values and the abilityof manmade wetlands to enhance sedimentation ofsuspended material are achieved within a relative-ly short time; wetland ability to assimilate nutrientsand toxic substances takes somewhat longer. Thediversity of a site and its ability to support morewildlife also generally increase over time. However,there is insufficient data at this time to say how longit takes for all the biological functions of a naturalwetland to develop.

WETLAND PRESERVATION VS.RESTORATION OR CREATION

Some States may call for protecting wetlandsequivalent in biological value to the wetlands filledor diked. Others, such as Oregon, prescribe thatno net loss of existing wetland values should oc-cur: “Oregon’s mitigation requirement . . . is thatareas of similar biological potential must be createdor restored, not simply protected (25). The mitiga-tion goal is to replace lost wetlands with restoredor new wetlands similar in quantity and quality offlora and fauna. Recently, the concept of “no netloss” has been criticized. The skepticism arises froma concern over whether new marsh creation reallycompensates for losses of natural wetlands. Raceand Christie (42), for instance, write:

A reevaluation of data from manmade marshesis necessary before there can be a determinationof whether coastal salt marshes are truly beingreplaced or expanses of marsh vegetation that per-sist temporarily are merely being planned . . . anewly created marsh is not the functional equiva-lent of a 1,000-year-old marsh,

These authors warn that mitigation should notbe offered as justification for the development anddestruction of wetlands. The assumed ability to‘ ‘create’ wetlands, they say, creates the percep-tion that wetlands are a renewable resource, aperception that could lead to more widespread de-velopment. Regulators, they feel, should be “ju-dicious” in allowing mitigation by marsh creation.Race and Christie conclude that:

Marsh creation in suitable situations can be aneffective tool to minimize onsite damage at post-construction sites, to abate shoreline erosion, andto return degraded wetlands to tidal influence bymeans of restoration. However, because of the lim-ited scientific evidence on the development and sta-bilization of important biotic and physical charac-teristics of manmade salt marshes, managers mustbe cautious in the widespread adoption of marshcreation as a mitigation strategy.

OPPORTUNITIES FOR WETLANDMITIGATION BANKING

The Statewide Interpretive Guideline for Wet-lands and Other Wet, Environmentally SensitiveHabitat Areas, adopted pursuant to the CaliforniaCoastal Act, provides for the payment of a fee toa public agency for purchase and restoration of adegraded wetland to a productive value at leastequivalent to that of a wetland being filled. Thepayment to a ‘‘mitigation bank’ would be in lieuof dedicating or restricting the use of a comparablewetland provided directly by the permitholder (36).This feature relieves the burden on landowners anddevelopers of searching out suitable mitigation sites.It also promotes a cohesive rather than afragmented approach to wetland-impact mitigation,with significant opportunity for economy of scale.

A Federal wetland bank, as suggested by theCorps, would operate as in California except thatcreation of replacement wetlands would be empha-sized (54). In fact, Congress has authorized use ofa wetland mitigation bank associated with the Ten-sas project in Louisiana.

Onsite Mitigation to MinimizeImpacts

Site-Specific Requirements

Many development activities produce primary,secondary, and cumulative impacts in or adjacentto wetlands that can be minimized feasibly whenfully understood. Thus, successful control of the pri-mary impact, in turn, will reduce subsequent sec-ondary and cumulative impacts. Further mitiga-tion efforts may be necessary, however, where anactivity is known to produce significant indirect or


compounding adverse effects. An areawide wetlandreview may uncover further unforeseen impacts.

One of the major problems in mitigating proj-ect impacts is the difficulty of mitigating cumulativeand secondary impacts. The lack of reliability inimpact prediction complicates the mitigation proc-ess. As an example, a short-term, isolated, primaryimpact of a dredging operation is suspension of sedi-ment in the water column. The narrow approachtoward mitigating this effect might include avoidingperiods of fast tidal currents and deploying silt cur-tains. However, secondary impacts may include therelease of excess nutrients and toxic contaminants.Long-term cumulative impacts from repeateddredging and other excavation at many sitesthroughout a single estuary might include low-level,but widespread, bioconcentration of metals andsynthetic organic compounds, with consequentchronic, sublethal effects within the food chain.Mitigative measures designed merely to minimizethe direct, localized effects of separate dredgingoperations may fail to address systemwide, indirecteffects.

General Requirements

Mitigating impacts on wetlands may take theform of standard conditions attached to individualdredge or fill permits, conditions incorporated intogeneral nationwide and regional permits, and thebest management practices (BMP’s) prescribed foractivities exempted from any permits. While thenature of general prescription has eased the regu-latory burden of issuing individual permits cover-ing site-specific situations and has set approximatestandards for common development practices, itoverlooks the likelihood of environmental damagethat may occur because specific wetland functions,values, and sensitivities are not considered. As anexample, disposal of spoil from maintenance dredg-ing might be required under a regional general per-mit to avoid discharge in or near active currents.This practice could lead to several shallow-waterspoil sites in a wetland area with long-term effects,such as chronic resuspension of sediments fromwind and waves, periodic disruption to bottom-dwelling populations, and possible bioaccumulationof toxic chemicals (37). Under an individual per-mit, however, site-specific conditions might stipu-late long-term disposal within a diked containment

site to avoid contamination of a nearby wetlandheron rookery or of a municipal ground watersupply.

BMP’s are applied to common activities such asminor road construction for maintenance of naturalsurface and subsurface drainage or pipeline installa-tion for sediment control. A representative BMPfor a minor road might be to install culverts throughthe causeway fill with spacing, elevation, andcapacity needed to maintain lateral drainage, in-cluding stormflows and the passage of fish and otheraquatic animals (37). The application of BMP’s onan indiscriminate basis can reduce the effectivenessof mitigation measures by overlooking limiting, site-specific conditions. To ensure their effectiveness,adequate site investigations are necessary to showthat critical or sensitive wetland values and func-tions are not jeopardized and that local environ-mental conditions will not negate normal BMP ef-fectiveness. For example, where there is unchan-neled sheet flow in a marshland, the required num-ber and spacing of culverts will be quite differentthan where surface flow is already channeled; other-wise, the usual BMP approach could cause adversehydrologic impacts by promoting channeling. Inconclusion, BMP’s generally are appropriate whereimpacts from a specified activity are localized, con-sistent, and predictable; the mitigative measuresare highly standardized and proven effective; andthe landowners or developers responsible possessthe necessary technological and management capa-bilities to use these practices effectively.

Controversy over mitigation arises over applica-tion of blanket stipulations of mitigation require-ments as opposed to case-by-case tailoring of per-mit conditions. Blanket stipulations greatly increasethe uncertainty over the effectiveness of mitigationrequirements, and developers complain that theyare required to meet blanket stipulations that arenot applicable to their specific permit situation.Because it lacks resources to undertake the exten-sive site investigations or studies to determine theeffectiveness of different mitigation measures, theCorps has been forced to use stipulations recom-mended by its staff and staff from other resourceagencies. GAO, in a report to the Congress on im-proving wetlands permit processing in Alaska,concluded:

Ch. 6—Impacts and Mitigation • 133

(The) Corps imposes controversial and costlypermit conditions without assuring that these con-ditions are, in fact, needed. The need for these con-ditions, which are frequently proposed by variousFederal and State agencies, is not substantiated bysite-specific data and research findings (12).

GAO recommended increased site-specific inves-tigation to prescribe impact controls adapted tounique site characteristics instead of blanket stipula-tions. This recommendation was aimed at the uni-form application of particularly costly measures thatmay burden the oil companies, such as seasonaldrilling requirements in wetlands. However, GAOadmitted that without more research to substanti-ate such restrictions, neither their imposition northe removal of blanket restrictions could be justified.

Uncertainty of Mitigation Cost Effectiveness

In the Corps’ proposed regulations for processingof section 404 permits, special conditions may beattached ‘‘only to respond to effects and impactsof the permit which are at least probable rather thanspeculative. 12 Banta and Nauman (2) believed that,‘‘While ideally (mitigation) involves an objectivejudgment by scientific standards . . . , it has fre-quently become the last ounce of environmentalquality that can be injected into a project withinlegally and politically acceptable limits. ” For ex-ample, a standard mitigation criterion in the En-vironmental Protection Agency’s (EPA) section404(b)(l) guidelines is to minimize adverse effectsby “selecting sites or managing discharges to pre-vent or avoid creating habitat conducive to the de-velopment of undesirable predators or species whichhave a competitive edge ecologically over in-digenous plants or animals. This much sophistica-tion actually applied to the conditioning of permitswould entail considerable subjectivity and specu-lation.

Clearly, there is more objectivity and accounta-bility where mitigation is prescribed in more specificterms tailored to local conditions, or at least toregional situations. On the other hand, a total site-specific approach would impose an inordinate regu-latory burden on both the permitters and permit-holders. Mitigation may not be cost effective where,as GAO has pointed out, costly measures for wet-

1 2 Feder~ Register, VO]. 45, No. 184, PP. 629 7 5 7 ”

land protection are requested without a site ex-amination to ascertain the need in each case. Also,requesting untested or (experimental) practices forimpact mitigation may be insupportable in view ofthe proposed regulation to eliminate conditioningof permits for speculative impacts. Unfortunately,the followup evaluation of actual cost effectivenessfor classes of mitigative measures has been verydeficient.

Management Plans

To design a mitigation plan covering secondaryand cumulative impacts in an area subject to signifi-cant development activities, a systemwide impactassessment such as that provided by the Corps’‘ ‘wetland review’ must be undertaken prior to de-veloping an estuary management-and-mitigationplan. The offsite, cumulative effects of many wet-land fills within an estuary on basinwide tidal cir-culation and water levels could be controlled by lim-iting the siting, uses, and overall amount of land-fills. Through this approach, appropriate resource-based constraints to development projects can beidentified based on an inventory of physical, bio-logical, esthetic, social, and economic resources.Objectives of the plan are linked consistently withall project proposals, and the costs are shared equi-tably.

Management plans are initiated generally bygroups that have responsibility for local planningand development. To help ensure that the plan willbe implemented, the sponsoring group may seekthe participation of the Corps and other agencieswith regulatory responsibilities. Management plan-ning efforts can be particularly useful for specificareas where pressures for development are intense,there are constraints to development, and incon-sistent policies and plans for an area make deci-sionmaking especially difficult.

Management plans can be used to define whichareas are to be protected or developed. For exam-ple, the Anchorage Wetland Plan classifies areasinto four categories: preservation, which precludesany development; conservation, which allows lim-ited development with mitigation measures; devel-opable, which allows complete draining and filling;and special study, which requires additional envi-ronmental data to determine status. The plan is be-


ing implemented through local planning and con-trol mechanisms and includes a provision for Fed-eral consistency with local coastal-management pol-icies. The Corps currently is preparing to issue ageneral permit to the city for development activitiesthat occur in wetlands covered by the plan (18).

Management plans also can be used to restrictcertain development activities and establish stand-ards for other types of development. For example,the East Everglades Management Plan prohibitsroad construction in permanent wetlands, allowsagricultural use in some drier areas (particularlythose that were disturbed previously), restricts thedensity of residential development, and definesBMP for three basic management areas. To imple-ment the law, the local government must developsome new mechanisms, including a site-alterationoverlay ordinance and a system of transferable de-velopment rights; establish new zoning districts;and continue to regulate obstructions to surface wa-ter flows under an existing ordinance. State govern-ment also has the responsibility of continuing toregulate dredge and fill in the area to the extentauthorized under State law and of revising water-quality standards for the area.

Continued regulation of section 404 by the Corpsis also an important element in the implementa-tion of the plan, particularly in cases of violations.Corps jurisdiction is broader than the State’s, andthe Corps has acted more quickly than the countyin enforcement actions (9).

Management plans also have been used to resolvethe conflicts and inconsistencies between the policiesof the numerous agencies with jurisdiction in anarea. For example, an objective of the Grays Har-bor (Washington) Estuary Management Plan is toset guidelines that offer some assurance that activ-ities permitted by the plan would have general con-currence from all the agencies involved. This plan-ning process is described in detail below.

The Grays Harbor Estuary Planning Task Forcewas formed in 1975 with representatives from allthe agencies responsible for plans and regulationsin the area. In 1976, funds were acquired from theOffice of Coastal Zone Management (OCZM) fordevelopment of the plan, which began with thedevelopment of a comprehensive data base deline-ating the physical and biological resources, owner-

ship, land use, comprehensive plan designations,areas of conflict, and other data. Development ofthe actual plan occurred during a series of work-shops in which the task force determined planningareas, established specific management units, anddeveloped policies to direct development activitiesin the estuary. The draft plan underwent extensivereview, and a final plan recently has been com-pleted.

The Grays Harbor Regional Planning Commis-sion is the lead agency for the plan but has no au-thority to adopt or enforce the plan. Instead, theplan is recognized as a recommendation from thetask force to the numerous agencies involved in theplanning process and in development activities inthe estuary. At present, an environmental impactstatement (EIS) on the plan is being prepared byOCZM.

Each of the agencies involved has been askedalso to prepare a memorandum of understanding(MOU) to explain how it perceives the plan, andhow it will be used. To date, none of the MOU’shave been completed and probably will not be untilthe EIS is finished. Unofficially, several agencieshave indicated that the plan probably will not beconsidered binding; however, it will be given seri-ous consideration in evaluation of local concernsand the public interest. The Fish and Wildlife Serv-ice (FWS) notes that it supports the plan; it has ac-cepted some major environmental losses in ex-change for long-term protection of other portionsof the estuary. FWS also observes that the plan doesnot make decisions but will serve as a guideline andshould streamline permit review. The Corps alsogenerally supports the plan. The Corps has beenasked to give serious consideration to issuing gen-eral permits for some activities in the area; in par-ticular, the disposal of dredge or fill material inunvegetated and vegetated intertidal areas desig-nated in the plan for industrial development. Todate, no decision has been made on these generalpermits.

A major issue in the plan is the predesignationof dredged-material disposal sites within the estu-ary. The Regional Planning Commission and thePort of Grays Harbor have expressed a strong de-sire for predesignation by EPA; to date, EPA hasnot made a decision on this issue. Since some of

Ch. 6—Impacts and Mitigation • 135

the areas are vegetated and unvegetated wetlandsof significant environmental value, EPA has ex-pressed some concern about whether such a pre-designation is legal.

State and local concerns about Federal involve-ment in the plan also have been expressed in an-other manner. The plan is viewed as an attemptto create a regional plan for shoreline managementthat will provide consistency and predictability forboth development and conservation interests.Through the planning process, least damaging al-ternatives and compromise solutions were inves-tigated and pursued.

Greater legal commitment of different Federalagencies to the results of any planning efforts of thissort are very much needed. If the Federal agen-cies cannot commit to the final components of theplan, then case-by-case permit evaluation will re-place long-term planning. Not only will predictabili-

ty and shortened permit processes be precluded,but other local jurisdictions will be discouragedfrom pursuing comprehensive shoreline planning,an outcome perceived to thwart the goals ofOCZM.

In spite of the concerns described above, the planis considered by many to have been a successfulexercise. Representatives from most of the jurisdic-tions involved felt it was a good idea and have com-mitted time and effort for almost 6 years. The portoften has been able to maintain momentum whenother agencies lost enthusiasm or became mired inthe process. Furthermore, many areas of ‘predict-ability’ have been identified. Development inter-ests can learn which are controversial locations andwhich are acceptable. At least some regulatoryagency personnel already are using the plan to assistthem in making decisions, even if they have not

firmly acknowledged its authority (45).

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