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32 A P P E N D I X D Risk Factors of BMP Characteristics
Category Characteristic Increases Wildlife Risk Reduces Wildlife Risk ImplementationChallenges/Considerations Permanent pool/dry between rain events Permanent pool or frequently ponded Dry between storm events Local stormwater regulations often require a permanent pool to enhance water quality treatment. If a pool is not provided, additional quality BMPs may be required. detimil ro dnuorgrednu / lessev desolCecafrus retaw desopxEecafrus retaw desopxe/lessev desolC access to water surface Closed vessels such as tanks or underground storage tend to be more costly per unit volume than excavated/graded features such as detention basins. They also provide reduced water quality benefits. lacol tub ,emit niard ruoh-84 mumixam seriuqer AAFsruoh 84 =< emit niarDDrain time > 48 hoursemit niarD stormwater regulations may require longer drain time to enhance water quality treatment retaw lacipyt <thgieh aidem ro aidem oNPMB ni aideM elevation Media height > typical water elevation to discourage water access by wildlife Media can be selected to provide a water quality filtration benefit, but will reduce BMP volume available for detention/quantity control. ot ssecca egaruocsid ro kcolb ot snoitcurtsbOsnoitcurtsbo ecafrus oNnoitcurtsbo ecafrus rehto/llab drib/eriW water by wildlife Wildlife obstructions may be costly and may impact or increase BMP operations and maintenance gnicneulfni rotcaf tnacifingis tsael eht si aera ecafruSsmrots neewteb orez / aera rellamSaera regraLretaw nepo fo aera ecafruS species utilization of ponds, but should still be considered. aw ot detaler si noitazilitu efildliWShallow (<0.50 m) or deep (> 1.0 m)Intermediate depth (0.50 m to 1.0 m)htped retaw lacipyT ter depth indirectly. Research shows that wildlife prefer an intermediate level of emergent vegetation, which would require an intermediate depth of water: shallow ponds can become choked with vegetation, reducing the attractiveness to wildlife while deep ponds will not allow vegetation to grow (not enough sunlight exposure) and will also reduce the attractiveness to wildlife. eneg si derots retaw fo emulov mumixam ehTemulov retaw deziminiMemulov retaw desaercnI)mrots ngised( derots retaw fo emulov xaM rally driven by local regulatory requirements for flood control and stream protection (reduction in peak flows and volumes), as well as extent of development. Low-impact development can help to reduce post-development runoff at the source and result in smaller BMPs. Average volume of water stored (design storm) Frequent and large volume of ponding Dry between storm events or infrequently ponded The average volume of water stored may be driven by design criteria (peak flow and volume restrictions, required design storms), extent of development, frequency of precipitation, and drain time. 1>>>htdiW:htgneLralugerrIoitar htdiw/htgneL Length:Width = 1 Airports may have limited space to implement, and available space may dictate length/width ratio. 1:2 gnimussa( AAF yb dednemmocer peetS)rettalf ro 1:3( wollahS)esir lacitrev :nur latnoziroh( sepols ediS or greater) Shallow slopes recommended to facilitate maintenance. .tcurtsnoc ot reisae osla era sPMB raeniLralucric ro raeniLralugerrIepyt retemireP itim evah ton yam stropriAslios gniniard-lleWslios gniniard ylroop ro cirdyh/deggolretaWetar noitartlifni/scitsiretcarahc lioS gation sites available with preferred soil characteristics. Hydric soils could be indicator of wetlands and possible permitting implications. .noitatipicerp revo lortnoc on evah stropriAstneve noitatipicerp tneuqerfnIstneve noitatipicerp tneuqerFllafniar fo ycneuqerF evo lortnoc on evah stropriAshtped noitatipicerp edutingam-rewoLshtped noitatipicerp edutingam-rehgiHsmrots ngised fo edutingaM r precipitation or selected design storms. Hydrology Perimeter Shape Exposure of Water Pond Surface Area/Size (continued on next page)
Type of vegetation within BMP Vegetation with high wildlife value (provides food or shelter) Vegetation with low wildlife value Vegetation may be a requirement of local permitting agencies to enhance water quality treatment; best to use vegetation that serves as a structural habitat and not a food source. ro mottob )suoivrepmi yllaitrap ro( suoivrepmImottob suoivrePmottob suoivrepmi ro suoivreP well-draining pervious bottom Impervious BMP bottoms will reduce water quality benefits from vegetation, eliminate the stormwater volume benefits offered by infiltration, and may increase stormwater management requirements or BMP sizing overall. A paved low-flow channel can reduce perviousness for most inundation conditions as well as facilitate access and sediment removal/maintenance. retaw egaruocsid ot retaW >> noitategeVretaW << noitategeVoitar retaw/noitategeV access by wildlife Selected vegetation should be drought and inundation tolerant to survive variations in BMP water levels. xednI ytisreviD woLxednI ytisreviD hgiHxedni ytisrevid/ycnetsisnoc noitategeV airetirC noitarapeS AAF nihtiW ro AOA edisnIAOA morf ecnatsiD (<10,000 ft.) Outside FAA Separation Criteria of 10,000 ft. Airports may have limited access/ownership of land outside of FAA separation criteria to allow for off-site mitigation. Regulatory criteria may require a mitigation ratio to increase the volume/performance of BMPs that are implemented offsite. Regulators typically also restrict mitigation to options within the same sub-watershed as the project. efildliw rehto ot evitaler sPMB retawmrots fo noitacoLmk 3 >mk 3 <serutaef retaw lanoitidda ot ytiniciV attractants can have a compounding effect on wildlife risk. Other wildlife risks off-property may be outside of airport's control. Increasing the distance between water bodies to 3 km or more, decreases the probability of avian usage by 50%. Location relative to designated important bird area (IBA) along migration flyway Within FAA-recommended 5 mi separation criteria Outside FAA-recommended 5 mi separation criteria Location of the BMP within the migration flyway can increase visibility and attractiveness of the BMP to wildlife. Location and elevation of BMP relative to aircraft movement pattern tfarcria ot evitaler sPMB retawmrots fo noitacoLmk 1 >mk 1 < movement patterns can significantly affect the likelihood of aircraft wildlife strikes. Geographic Location Vegetation Category Characteristic Increases Wildlife Risk Reduces Wildlife Risk ImplementationChallenges/Considerations
