chapter 7 highway surveying

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MITIGATION OF ENVIRONMENTAL

IMPACTSFrom Introduction toTransportation Engineering

by James H. Banks



Mitigation of Environmental Impacts

• Mitigation of environmental impacts is an action tolessen t!eir severity.

• It is an important part of t!e planning design andoperation of transport facilities.

• Mitigating measures may consist of"

•facility design modifications• #onstruction of artificial !abitats or replacement!ousing

• Modifications to t!e operation of facilities and

systems



Noise

• $oise is an important impact for most transportationsystems.

• It is per!aps most important in t!e case of airtransportation %!ere noise impacts around ma&orairports are often severe.

• $oise impacts of !ig!%ay and rail systems tend to be

less severe.



Noise

• Mitigation of noise impacts includes"

• #ontrol of noise at t!e source

• 'ocation and design of facilities to minimi(enoise impacts

• #onstruction of noise barriers

• Insulation of receptors• In a fe% e)treme cases purc!ase of impacted

property and abandonment of incompatibleland uses.



Airport Noise Mitigation

• T!e Federal *viation *dministration +F**, !asestablis!ed a classification system indentifying four

land-use guidance (ones based on noise levels.• one * %!ere sound pressure level is less t!an // dB*

• one 0 %!ere sound pressure level e)ceeds 1/ dB*

• ones * and B are suitable for residential development

• one 0 is generally restricted to activities suc! asmanufacturing transportation and agriculture



ig!"a# an$ Rail Noise Mitigation

• Hig!%ay noise is nearly continuous %!ile railnoise is more sporadic.

• T!e most common mitigating measures for!ig!%ay and rail noise are noise barriers ormodification of profile to depress t!e facility

belo% ground level.



Encroac!ment on Nat%ral a&itats

• #onstruction of transportation facilities of alltypes is apt to encroac! on natural !abitats.

• 2ld-gro%t! forest riparian vegetation andcoastal (ones

• Transportation facilities may disturb natural

areas directly by means of noise visualintrusion fumes and conflicts bet%een %ildlifeand ve!icles.

• It may also act as barriers to %ildlife migration.




• T!ey almost al%ays !ave some impacts on bot!!ydrology and %ater 3uality %!ere %etlands areinvolved.

• Temporary impacts during construction are !ig!level of direct disturbance to %ildlife and

temporary %ater 3uality impacts due to erosion




• Federal la%s related to t!e mitigation of !abitatencroac!ment"

• #lean 4ater *ct %!ic! re3uires t!e protectionof %etlands

• Endangered 5pecies *ct re3uires agencies to

ensure t!at t!eir actions do not &eopardi(e t!ee)istence of any t!reatened or endangeredspecies.



Storm"ater Managament

• 5torm%ater disc!arges from transportationfacilities can contribute to flooding andadversely impact %ater 3uality do%nstream.

• #onstruction of impervious surfaces suc! aspavements alters t!e relations!ip bet%een

rainfall and runoff6 suc! surfaces also serve as asource for a variety of contaminants.



A'AR(O)S *ASTE AN( SOILCONTAMINATION

• Ha(ardous %aste and contaminated soils areoften present in t!e rig!ts-of-%ay oftransportation facilities.

• T!e activities of transportation agencies +forinstance certain maintenance activities, may

generate !a(ardous %astes t!at re3uire disposal.



A'AR(O)S *ASTE AN( SOILCONTAMINATION

• 7emediation %ill be planned and carried out byspeciali(ed environmental engineering firms.

• 'andfilling contaminated material may be removedand placed in an approved landfill.

• #ontainment t!is involves sealing off !a(ardous %asteor contaminated soil by means of capping grout

curtains slurry %alls s!eet piles or encapsulation inconcrete vaults or bridge abutments.

• Treatment t!ese include incineration solidification orstabili(ation bioremediation and vacuum e)traction.

chapter 7 highway surveying

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