June 12, 2018: Bats & Bridge Inspections

Source: DOT Environmental Division

Here at Lotus, the environmental scientists and planners have worked on numerous bridge rehabilitation and replacement projects through Pennsylvania, Maryland, and Delaware.  In Pennsylvania specifically, new changes have been implemented regarding endangered bat species and bridge inspection requirements.

There are two federally listed bat species in Pennsylvania, the Indiana Bat and the Northern Long-eared Bat.  In February 2018, the Programmatic Biological Opinion for Transportation Projects in the Range of the Indiana Bat and the Northern Long-eared Bat generated by the Federal Highway Administration (FHWA), Federal Railroad Administration (FRA), Federal Transit Administration (FTA) and the U.S. Fish and Wildlife Service (USFWS) was revised. 

Source: DOT Environmental Division

Lotus has been made aware that the USFWS is requesting bridge inspections for these endangered bats at the time of PA Department of Environmental Protection (PADEP)/U.S. Army Corps of Engineers (USACE) permit submissions for bridge or structure rehab and replacement projects that have PNDI hits for bats.  The following information is taken from Appendix D: Bridge Assessment Guidance (DOT Environmental Division):  

Many concrete bridges that span larger rivers in wide floodplains offer excellent areas for roosting.  These areas tend to have ample food supply and may serve as historic flyways for bats during migration (i.e. March – May and September – November).  These bridges may also offer opportunities for mating in late fall.  The cracks in concrete in the ceilings or walls and protective expansion joints also create a damp, dark ‘cave-like’ environment that is ideal for bat habitats.

Preliminary Indicators of Bat Presence:  The following physical observations can be easily made for bridges and the presence of just one of these signs on a bridge during the assessment is enough documentation to confirm bat usage.  Negative surveys are considered valid for one year.

Source: DOT Environmental Division

Visual & Sound

Bats flying or roosting (hanging), this usually occurs at least four feet from the ground.

High pitched squeaking or chirping, this may be helpful in locating bats within deep cracks or open joints of the bridges.

Source: DOT Environmental Division


Bat droppings (also known as Guano) are small brown or black pellets.  Older droppings may be gray in color.   These will accumulate on the ground, floor of a covered bridge, or on structural components below roosting bats.  

Source: DOT Environmental Division


These may appear as wet, 4 to 6-inch-wide dark stains located on concrete support beams and walls immediately below the ceiling of the bridge, and beneath joints.  

According to the language outlined on the Bridge/Structure Assessment Form, Assessments must be completed no more than 2 years prior to conducting any work below the deck surface on all bridges, regardless of whether assessments have been conducted in the past.

Any bridge or structure suspected of providing habitat for any species of bat will be removed from work schedules until the DOT has coordinated with the USFWS. Additional studies may be required to determine what species may be utilizing the structures prior to allowing any rehabilitation or replacement work to proceed. Any questions should be directed to the project’s District Environmental Manager.

                                                                                                       To view the full Guidance Form, please follow the link below: