Houghton Road Widening at Union Pacific Railroad: Bat Roost Mitigation

Transcription

1 Houghton Road Widening at Union Pacific Railroad: Bat Roost Mitigation RTA Wildlife Linkages Project Funding Proposal Prepared for: City of Tucson Department of Transportation 201 N. Stone Ave. Tucson, AZ and Pima County Department of Transportation 201 N. Stone Ave. Tucson, AZ Prepared by: EcoPlan Associates, Inc. 78 W. Cushing St. Tucson, AZ EcoPlan No April 26, 2013

2 TABLE OF CONTENTS 1. Introduction... 1 A. Proposal Purpose... 1 B. Project Background Project Impacts Proposed Mitigation Measures... 4 A. Methods and Recommendations for Excluding Bats... 5 B. Roost Design... 6 C. Mitigation Compliance/Success Budget Overview Contacts Literature Cited... 8 Detailed Cost Estimates...9 Proposal for RTA Wildlife Linkages Funding i Houghton Road Widening at Union Pacific Railroad

3 APPENDICES I. Bats and Bridges A. Literature Cited II. History of Bat Usage of the Houghton Road UPRR Bridge A. Pallid Bat B. Big Brown Bat C. Cave Myotis D. Mexican Free-tailed Bat E. Literature Cited III. Description of Proposed Bridges IV. Mitigation Plan A. Mitigation Planning B. General Timeline C. Location of Roost Structures in the New Bridge D. General Designs for Prototype Habitat Structures i. Maberry Bridge Condo ii. Concrete Panels Attached to the Vertical Sides of the I-beams iii. Texas Bat Abodes Modified for the Tucson Climate E. Literature Cited V. Temperature Requirements and Current Conditions A. Summer Temperatures B. Winter Temperatures C. Spring and Fall Temperatures D. Overview: Temperature E. Existing Conditions and Temperatures F. Literature Cited VI. Monitoring A. Before Construction and During Construction B. After Construction C. Literature Cited Proposal for RTA Wildlife Linkages Funding ii Houghton Road Widening at Union Pacific Railroad

4 1. INTRODUCTION A. Proposal Purpose The purpose of this proposal is to request Regional Transportation Authority (RTA) Wildlife Linkages funding in support of bat mitigation related to the Houghton Road widening project. The project is along Houghton Road in Tucson and in unincorporated Pima County, Arizona, approximately 1.5 miles north of Interstate 10 (Figure 1 Project location and Figure 2 Project vicinity). The project is on the section line between Sections 35 and 36 in Township 15 South, Range 15 East on the Tucson SE (1992), Arizona, U.S. Geological Survey (USGS) 7.5-minute quadrangle. The bridge is structurally deficient, load limit restricted, and does not meet the future RTA plans for Houghton Road corridor improvements. Current and future traffic needs necessitate widening Houghton Road and replacing the Union Pacific Railroad (UPRR) bridge with a larger, modern structure capable of supporting the increased traffic. The existing bridge provides roost habitat for several thousand bats of four species, including three species with maternity colonies. The City of Tucson and Pima County intend to maintain roosting populations of bats on the new Houghton Road UPRR bridge. It has been known that bridges provide roosting habitat in urban environments (Appendix I), and the Houghton Road UPRR bridge in particular is known to support a healthy bat population (Appendix II). This proposal presents strategies to (1) exclude bats from the existing bridge prior to its demolition while simultaneously providing alternative habitat structures on the new northbound bridge, (2) test various designs and locations for bat roosts on the current bridge to maximize the potential for colonization and promote occupation when construction of the new bridge is complete, and (3) document mitigating measure compliance for exclusion activities and the success of the habitat structures provided in the new bridge. B. Project Background The City of Tucson, in conjunction with Pima County, is planning to replace the existing twolane bridge that crosses over the UPRR tracks on Houghton Road with a new six-lane divided bridge structure. The existing structure is a seven-span precast concrete inverted U-beam bridge built in In the years since its construction, four species of bats have adopted the bridge as a day roost; three species are also using it as a maternity roost, occupying the spaces (crevices) between the U-beams. Currently, Houghton Road in the project area consists of one travel lane in each direction. The roadway width is about 28 feet. The existing UPRR bridge includes two 13-foot-wide travel lanes, 1-foot-wide shoulders, and 4-foot-wide sidewalks, for a total width of 36 feet. The purpose of this project is to replace the bridge. The roadway and bridge geometry would also be improved to satisfy current design standards, thereby improving sight distances and providing bicycle and pedestrian facilities (Appendix III). Proposal for RTA Wildlife Linkages Funding 1 Houghton Road Widening at Union Pacific Railroad

5 Project Location Houghton Road Widening at Union Pacific Railroad Figure 1. Project location Proposal for RTA Wildlife Linkages Funding 2 Houghton Road Widening at Union Pacific Railroad

6 Tanque Verde Road ~ 10 miles E Old Vail Road UPRR Begin Project E Mary Ann Cleveland Way E Old Vail Road Houghton Road UPRR bridge S Houghton Road End Project!"a$ North Miles Base map: Keams Canyon (1991), Arizona, USGS 7.5' Topographic Series (ESRI Online Resources 2013) Houghton Road Widening at Union Pacific Railroad Figure 2. Project vicinity W\13-441\BIO\FundProp\Fig2 Proposal for RTA Wildlife Linkages Funding 3 Houghton Road Widening at Union Pacific Railroad

7 This project is part of an overall plan by the Tucson Department of Transportation to meet future traffic needs by widening Houghton Road between Tanque Verde Road and Interstate 10 to a four-lane and six-lane facility that would serve as a major north south arterial. Planning and design for this project are under way. Construction is tentatively scheduled for Construction for the bridge includes federal and local funding. The Arizona Department of Transportation and the Federal Highway Administration (FHWA) granted environmental clearance for the project on August 1, 2012, under federal project number STP-TUC-0(201)A and ADOT number 0000 PM TUC SS624 01C. The environmental clearance includes commitments to mitigate the impact of lost bat roosts and the requirement from FHWA to humanely exclude bats from the existing bridge. Final design is currently under way. Construction scheduling allows for a unique opportunity to test various bat habitat structures on the old bridge while the new northbound bridge is being built and move them to the new northbound bridge before the old bridge is demolished. The short time frame (may be less than a month) between when the new northbound bridge is complete and open to traffic and the old bridge is demolished will require biologists to exclude bats from the old bridge while simultaneously providing them with previously tested habitat structures on the new northbound bridge. 2. PROJECT IMPACTS The Houghton Road UPRR bridge is considered one of the most important bridges for bats in the Tucson area (Wolf and Shaw 2002; Tim Snow, personal communication) based on species diversity, the abundance of bats, and its year-round use (Appendix II). The Houghton Road UPRR bridge is used as a maternity colony structure and as a roost structure by migrating bats. Four species of bats have been confirmed to use the bridge: Mexican free-tailed bat (Tadarida brasiliensis), cave myotis (Myotis velifer), big brown bat (Eptesicus fuscus), and pallid bat (Antrozous pallidus) (Wolf and Shaw 2002; Sandy Wolf, biologist, unpublished data). Mexican free-tailed bats occupy the bridge year-round. Documentation in 2011 of the bridge s use as a maternity site for three species Mexican free-tailed, big brown, and pallid bats further increases its significance, as does the apparent increase in numbers of Mexican free-tailed bats at the bridge. The new bridge deck will lie directly in contact with the top of the support girders and will provide no crevices or cavities that are potentially suitable for roosting bats. Without the proposed mitigation measures, the new bridge would, at most, potentially only provide night roosting habitat because bats often prefer to rest on the open lateral surface of exposed support girders (Keeley and Tuttle 1999). The addition of structures to the new bridge conducive to bat use as roosting and maternity colony sites will help maintain this important bat colony. 3. PROPOSED MITIGATION MEASURES Mitigating the loss of this important bat roost consists of (1) testing various roosts designs for potential installation on the new bridge, (2) preventing mortality and the disruption of reproduction when the existing bridge is demolished and the new bridge is constructed (required FHWA mitigation), (3) retrofitting the new bridge with roost habitat that re-creates the structural and thermal characteristics of the current roosts to maximize the probability that bats will move from the existing bridge to the new bridge, and (4) monitoring the bat population throughout the Proposal for RTA Wildlife Linkages Funding 4 Houghton Road Widening at Union Pacific Railroad

8 process and after the new bridge is fitted with roosts to evaluate success (Appendix IV). The timing of construction and mitigation events is crucial to avoid disturbance, injury, mortality, or negatively affected reproduction, and to increase the probability of successful relocation (Appendix IV). The general mitigation goals are that: No bats are killed during demolition because exclusion was not complete or was ineffective. Bats will be excluded during a time period that minimizes negative effects on their survival and reproduction. Bats occupy the new bridge in the same general numbers, are of the same species, and use the new bridge in the same way. Bat roosting habitat is maintained for the life of the new bridge. A. Methods and Recommendations for Excluding Bats Habitat structures must be installed on the new northbound bridge, and then bats must be safely excluded and all crevices sealed to prevent reentry before the existing bridge is demolished. The ability to fully exclude bats from the current structure is contingent on obtaining the appropriate permissions from the UPRR for access to its right-of-way. Without this permission, full exclusion is not possible. Because bats are in the bridge year-round, bats would inevitably be killed during demolition. With permission from the UPRR and through the implementation of proper methods and the following recommendations, injury, mortality, and negative effects can be minimized. Excluding bats by sealing the crevices in the bridge poses one of the more difficult logistical challenges and may require the use of experienced professional insulation installers. Though experienced insulation installers may increase the expense associated with this task, using experienced installers will ensure that crevices in the existing bridge are properly sealed in the most efficient manner and with the least impact to bats occupying the structure. A qualified biologist will accompany the insulation installation crew at all times to ensure the safety of the bats. To ensure the safety of the bats during the transition period: Exclusion and sealing will occur after roost habitat is installed in the new bridge to provide bats with alternative roosts at the same location rather than forcing them to relocate to other areas. Bats will be excluded from the existing bridge and the crevices will be sealed when bat numbers are lowest from November through mid-march. Bats will be excluded during the warmest times during this period, when active exclusion would least likely stress bats, particularly if they do not relocate to the new habitat. Bats will be excluded before they begin arriving to the bridge in the spring to form maternity colonies. Every crevice in the existing bridge must be sealed, including those over the railroad tracks and those that are rarely used now. Bats currently use crevices over the tracks, and those excluded Proposal for RTA Wildlife Linkages Funding 5 Houghton Road Widening at Union Pacific Railroad

9 from their preferred crevices in other spans may move either to the span over the railroad tracks or to previously unused crevices in the bridge. Exclusion and sealing over the railroad tracks will require cooperation by the UPRR. Sufficient lead time is necessary for planning and for efficient and successful execution. Seals will be checked periodically to ensure that they eliminate the possibility for reentry by bats. If a seal fails, bats must be excluded again before resealing. The frequency of site visits will vary, with more frequent checks in the early weeks after sealing and fewer checks as it is determined the measures are working. The bridge will be surveyed immediately prior to demolition to ensure that all seals are in place and no bats remain. The general method will be to have a qualified biologist survey each crevice in the bridge during the day with a spotlight and binoculars. If the crevice is unoccupied by bats, it will be sealed immediately with expandable foam injected into the crevice. The ends of the crevice will be sealed (with hardware cloth or foam) to prevent bats from entering from the sides after the bottom is closed. For crevices that are occupied by bats, we will wait until after the bats exit in the evening and then seal the crevice. If not all bats leave the crevice, they can be encouraged to leave by inserting a stick with LED lights along it into the crevice near the bats. Typically, bats avoid the light and fly out. Though this technique forces bats to leave, it is unlikely to have a negative effect on them if it is done during mild temperatures, clear weather, and when most of the colony has already left for the evening. This technique was used successfully to exclude many Mexican free-tailed bats from another Tucson bridge being resurfaced (Sandy Wolf, biologist, unpublished data). If exclusion is done properly, and seals are checked periodically and maintained up to demolition, injury or mortality will be minimized. B. Roost Design Mitigation efforts to provide roost habitat at the new Houghton Road UPRR bridge are more likely to be successful by using a variety of designs and roost locations in the new bridge. Because the design of the new bridge differs from the existing bridge, the same characteristics of the existing habitat cannot be re-created in the new bridge. Though the depth and width of the crevices can be replicated, the degree of thermal moderation and temperature profiles cannot be predicted because the materials used to create the crevices, and their position relative to the bridge deck, will be different. This funding proposal includes a test of different replacement bat roosts to be placed on the existing bridge. This will allow the biologists to better determine the optimum roost type and sizing. Appendix IV details bridge design suggestions, including the location and potential new roost structures types, and Appendix V details the temperature requirements of the four bat species currently using the bridge and the conditions in the existing bridge. C. Mitigation Compliance/Success The significance of a roost site, and therefore the relative success of mitigation efforts, cannot be judged by the number of bats alone. For example, the number of pallid bats roosting in the existing bridge is small compared with the number of Mexican free-tailed bats in the bridge, but Proposal for RTA Wildlife Linkages Funding 6 Houghton Road Widening at Union Pacific Railroad

10 the bridge may be much more important to the pallid bat population in the area than it is to the more numerous species. Because of natural history traits such as its diet, small home range, larger body size, and thermal tolerances, potential roost sites may be much more limited in the Tucson area for pallid bats than for Mexican free-tailed bats. As another example, maternity colonies have more restrictive requirements for day roosts than do bats using a roost as a temporary migratory stopover. Though the old bridge is used by migrating bats, use of the new bridge only by migrating bats, even in large numbers, is not fully successful mitigation. The use of the bridge by multiple species in multiple ways, including as a maternity roost and its use by large numbers of bats, is what makes this bridge so special and what makes successful mitigation difficult. For the Houghton Road UPRR bridge, mitigation can be considered successful when the new bridge is occupied by: Mexican free-tailed bats in significant numbers in the summer and early fall (including a maternity colony) and in lesser numbers in late fall to early spring Pallid bats a maternity colony and migrating bats in late summer and fall Big brown bats a maternity colony Cave myotis migrating bats in late summer and fall A thorough study of the temperature regime in the old bridge is necessary to ensure that the habitat structures in the new bridge mimic this regime as closely as possible, encouraging similar use of the new bridge compared with the old bridge. Applying numerical criteria for each species based on the present occupation and use is tempting, but the outside factor of development (commercial and residential growth) in the immediate project vicinity and region may influence future bat habitation. Ideally, bats would return after bridge construction in the same magnitude as documented in Another important criterion for successful mitigation is that roost habitat lasts the lifetime of the bridge and is maintained to ensure that desirable conditions do not change or deteriorate. Even if dimensions, characteristics, and temperature regimes in the new habitat duplicate those in the existing bridge, it may take a few years for bats to occupy the new habitat. If winter and summer temperature regimes in newly installed roost structures are not the same as in the existing bridge, modifications will be made as soon as possible to increase the likelihood of success. Appendix VI expands on the suggested monitoring regime. Proposal for RTA Wildlife Linkages Funding 7 Houghton Road Widening at Union Pacific Railroad

11 4. BUDGET OVERVIEW The following budget summary covers activities for an approximate 3-year period beginning with bat roost testing on the existing bridge in 2013 and concluding after the new northbound and southbound bridges are constructed (construction estimated to be in 2015). The funding proposal for RTA consideration focuses on the local jurisdiction s mitigation commitments. The measures related to bat exclusion activities required through the project environmental clearance by the FHWA are not shown as a cost component of the RTA funding, but they would be a project cost element of the bridge s federal funding by the FHWA. A more detailed cost estimate showing labor hours, equipment, and direct expenses is provided at end of the proposal. Task 1 Bat Roost Structure Type Testing (existing bridge) Install and test Maberry condos, modified bat abode, concrete panels* Install data loggers (temperature sensors) Subtotal $32,623 Task 2 Bat Roost Installation on New Northbound Bridge Remove bat houses from existing bridge* Install bat houses and data loggers on new northbound bridge* Subtotal $28,018 Task 3 Bat Exclusion Activities, Existing Bridge (in-kind cost contribution)** Inspect crevices and seal* Reinstall failed seals as needed* Subtotal $0 Task 4 Project Compliance Regularly inspect roost for species, numbers, activity Monitor and record temperature data Modify habitats structures, as needed Prepare summary report Subtotal $27,735 Grand Total $88,376 * Activity would be conducted by licensed construction contractor with oversight by EcoPlan Associates, Inc., biologists and Pima County Department of Transportation Engineering and Maintenance divisions. ** Cost ($18,214) not included in RTA funding proposal. 5. CONTACTS Tim Snow, bat specialist, Arizona Game and Fish Department Non-game Research Branch, provided copies of reports by Keeley and Tuttle (1999) and Johnston et al. (2004) as well as his insights into the project. Sandy Wolf, bat specialist, provided data. 6. LITERATURE CITED Johnston D., G. Tatarian, and E. Pierson California bat mitigation, techniques, solutions and effectiveness. Prepared for the California Department of Transportation and California State University Sacramento Foundation, Sacramento, California. Keeley B.W., and M.D. Tuttle Bats in American bridges. Bat Conservation International. Resource Publication No. 4. Wolf, S.A., and W.W. Shaw Roost selection of bridges by bats in an urban area. AGFD Heritage Grant (U98007), Final Report. Proposal for RTA Wildlife Linkages Funding 8 Houghton Road Widening at Union Pacific Railroad

12 DETAILED COST ESTIMATES Proposal for RTA Wildlife Linkages Funding 9 Houghton Road Widening at Union Pacific Railroad

13 Proposal for RTA Wildlife Linkages Funding 10 Houghton Road Widening at Union Pacific Railroad

14 Task 1: Bat Roost Structure Type Testing P. Dockens, Sr. Field M Dawson, Project S. Wolf, Staff: Sr. Field Biologist Biologist Manager R. Hunt, Biologist Order and assemble bat habitat structures Install bat roosts and data loggers (existing bridge); assume 2 days Meetings, planning with UPRR, county 8 16 engineers K. Thielmann, QC/Tech. Editor Direct Expenses Habitat installation (subcontracted) $8,000 Maberry condos $4,500 each* $13,5000 Concrete panels $400 each* $2,000 Modified Texas bat abodes $500 each* $1,500 Lift rental for temp loggers 2 $170/day $340 Temp data loggers $18 each $450 Miscellaneous hardware (fasteners, insulation, $200 epoxy, etc.) Mileage** $66 * Initial purchase 3 condos, 3 abodes, and 5 panels for Task 1. Subsequent structures purchased, as needed, for Task 2. ** Mileage based on 4 30 miles $0.55 mile = $66. Proposal for RTA Wildlife Linkages Funding 11 Houghton Road Widening at Union Pacific Railroad

15 Task 2: Bat Roost Installation on New Northbound Bridge P. S. Wolf, Dockens, Sr. Field Sr. Field Biologist Biologist M Dawson, Project Manager R. Hunt, Biologist K. Thielmann, QC/Tech. Editor Staff: Remove bat habitat structures from existing bridge Install bat habitat structures and data loggers on new northbound bridge Direct Expenses Habitat installation (subcontracted) $8,000 Maberry condos $4,500 each, as needed $13,500 Concrete panels $400, as needed $2,000 Texas bat abodes $500, as needed $1,500 Temp data loggers $18 each $450 Lift rental 2 $170/day $340 Mileage* $33 * Mileage based on 2 trips at 30 miles $0.55 mile = $33. Proposal for RTA Wildlife Linkages Funding 12 Houghton Road Widening at Union Pacific Railroad

16 Task 3: Bat Exclusion Activities (in-kind services, not part of RTA funding request) P. Dockens, Sr. Field Staff: S. Wolf, Sr. Field Biologist Biologist Inspect crevices and seal (assume 3 days) Reinstall as needed (assumes 4 events, half day each) Direct Expenses Foam insulation (material) M Dawson, Project Manager R. Hunt, Biologist K. Thielmann, QC/Tech. Editor Initial seal, plus up to 4 revisits $2,600 to patch Contractor installation of foam exclusion $9,000 Lift rental 4 $170 day $680 Mileage $115 * Mileage based on 7 30 miles $0.55 mile = $ Proposal for RTA Wildlife Linkages Funding 13 Houghton Road Widening at Union Pacific Railroad

17 Task 4: Project Compliance (monitor and report on exclusion activities and roost success; total period: 3 years) P. M K. Dockens, Dawson, Thielmann, Sr. Field Project R. Hunt, QC/Tech. Biologist Manager Biologist Editor S. Wolf, Sr. Field Biologist 108 Staff: Monthly: inspect roosts for species, numbers, and activity (for 4 years) Monitor/record temperature (periodic for 72 4 years) daytime and night readings Modify habitat structures (as needed) Summary Report Direct Expenses Lift rental 3 $170/day $510 Mileage* $891 * Mileage based on miles $0.55 mile = $891. Proposal for RTA Wildlife Linkages Funding 14 Houghton Road Widening at Union Pacific Railroad

18 APPENDICES Proposal for RTA Wildlife Linkages Funding 15 Houghton Road Widening at Union Pacific Railroad

19 I. BATS AND BRIDGES Throughout history, bats have been feared and maligned. In recent years, with an increased understanding of bat ecology and their importance in plant pollination and controlling insect pests, considerable effort has been made to educate the public and to conserve bats and the places where they live (Keeley and Tuttle 1999). The importance of bridges as roosting structures for bats has been reported commonly in literature in North America (Adam and Hayes 1996, Barbour and Davis 1969, Keeley and Tuttle 1999, Kunz 1982, Perlmeter 1995) and in the British Isles (McAney 1992, Norman 1995, Roberst 1989, Smiddy 1991). The use of bridges by bats in the desert southwest has been addressed in several publications (Davis and Cockrum 1963, Hirchfeld et al. 1977, Sidner 1997, Wolf and Shaw 2002). Wolf and Shaw (2002) provide survey information for 43 bridges in the Tucson area and include specific information concerning bats occurring at the Houghton Road UPRR bridge. Bats have declined in numbers for reasons that include the use of pesticides and the destruction of foraging and roosting habitat. Disturbance of bat roosts and other disturbances of bats by humans are thought to have contributed to population declines of bats (McCracken 1986, 1988; Stihler and Hall 1993; O Shea and Vaughn 1999). However, it is apparent that some species of bats can live in occupied buildings, bridges, and other man-made structures in populated areas. In these situations, bats have become accustomed to human activity, traffic, noise, and vibrations. As human activity continues to alter the natural environment, potentially reducing available natural bat roosting habitat, some bats have come to increasingly use man-made structures (Keeley and Tuttle 1999). At least 24 of the 45 bat species in the United States are known to use linear transportation bridges as day and night roosts, and several other species probably do as well (Keeley and Tuttle 1999). Bridges, particularly older bridges, provide structural features, crevices, and holes often leading to cavities that are similar to natural roost locations, such as caves and crevices in cliffs and rock outcrops. These sites are most often elevated, providing convenient aerial access to bats as well as protection from predators. Due to their mass, bridges warm and dissipate heat slowly, providing insulation from rapid temperature changes (Johnston et al. 2004). In cool weather, the heating of the bridge deck in the sun and the insulation afforded by the mass of the deck, supporting beams, and girders provide protection from wind, and warmer and more constant temperatures, than of the surrounding air (Perlmeter 1996, 2004; Pierson et al. 1996). From a human standpoint, bridges, among other man-made structures, are ideally most suited for use by bats. They are neither lived in nor used as a workplace by humans, and their function as a transportation structure often does not conflict with their suitability as a roosting location for bats. Keeley and Tuttle (1999) point out that cost-efficient modifications can be incorporated into new bridge design and construction or can be added to existing bridges to provide homes for millions of bats. As the emphasis on environmental education and conservation has become widespread in the United States, the importance of bats in the pollination of plants and insect control has been better understood. Many city and government entities have come to realize that protecting bats is in the best interest agriculturally and for their communities and the natural environment. There is Proposal for RTA Wildlife Linkages Funding 16 Houghton Road Widening at Union Pacific Railroad

20 increased interest in conserving existing bat roosting habitat and providing additional roosts or replacing roosting habitat when infrastructure elements supporting bat roosts are improved, removed or replaced (Keeley and Tuttle 1999). A. Literature Cited Adam, M.D., and J.P. Hayes Use of bridges by bats as night roosts in the Oregon coast range. Suislaw National Forest, U.S. Forest Service and Bureau of Land Management, Eugene District, Oregon. Barbour, R.W., and Davis, W.H Bats of America. University of Kentucky Press, Lexington, Kentucky. Davis, R., and E.L. Cockrum Bridges used as day roosts by bats. Journal of Mammalogy 44: Hirchfeld, J.R., Z.C. Nelson, and W.G. Bradley Night roosting behavior in four species of desert bats. The Southwestern Naturalist 22: Johnston D., G. Tatarian, and E. Pierson California bat mitigation, techniques, solutions and effectiveness. Prepared for the California Department of Transportation and California State University Sacramento Foundation. Sacramento, California. Keeley B.W., and M.D. Tuttle Bats in American bridges. Bat Conservation International. Resource Publication No. 4. Kunz, T.H Roosting ecology of bats. In Ecology of bats, edited by T.H. Kunz, pp Plenum Publishing, New York. McAney, K Bats and bridges: A report on the importance of bridges to bats. National Parks and Wildlife Service, Galaway, Ireland. McCracken, G.F Why are we losing our Mexican free-tailed bats? Bats 3: Who s endangered and what can we do? Bats 6:5 9. Norman, G.M Bats and bridges in Cumbria. The Carlisle Naturalist 3: O Shea, T.J., and T.A. Vaughn Population changes in bats from central Arizona: 1972 and The Southwestern Naturalist 44: Perlmeter, S.I Bats and bridges: Patterns of night roost use by bats in the Willamette National Forest. Bat Research News 36(2&3): Bats and bridges: Patterns of night roost activity in the Willamette National Forest, pp , in Bats and Forest Symposium (R.M.R. Barclay and M.R. Brigham, editors), October 19 21, 1995, Research Branch, British Columbia. Ministry of Forests, Victoria, British Columbia, Canada. Proposal for RTA Wildlife Linkages Funding 17 Houghton Road Widening at Union Pacific Railroad

21 Bats and bridges: A field study of the thermal conditions and social organization of night roosts in the Willamette National Forest 2nd Bats and Forests Conference. Abstract. Hot Springs, Arkansas. Pierson, E.D., W.E. Rainey, and R.M. Miller Night roost sampling: A window on the forest bat community in northern California. In Bats and forest symposium (R.M.R. Barclay and M.R. Brigham, editors), October 19 21, 1995, pp Research Branch, British Columbia. Ministry of Forests, Victoria, British Columbia, Canada. Working Paper 23/1996. Roberst, D Bats under bridges in North Yorkshire. Bat News 16:6 7. Sidner, R.A Studies of bats in southwestern Arizona with emphasis on aspects of life history of Antrozous pallidus and Eptesicus fuscus. Ph.D. dissertation, University of Arizona, Tucson. Smiddy, P Bats and bridges. Irish Naturalist Journal. 23: Stihler, C.W., and J.S. Hall Endangered bat populations in West Virginia caves gated or fenced to reduce human disturbance. Bat Research News 34:130. Wolf, S.A., and W.W. Shaw Roost selection of bridges by bats in an urban area. Arizona Game and Fish Department Heritage Grant (U98007), Final Report. Proposal for RTA Wildlife Linkages Funding 18 Houghton Road Widening at Union Pacific Railroad

22 II. HISTORY OF BAT USAGE OF THE HOUGHTON ROAD UPRR BRIDGE The Houghton Road UPRR bridge is a concrete bridge constructed of inverted U-beams laid parallel and overlain by asphalt pavement. Vertical spaces between the beams form crevices where bats can enter from the bottom and roost. Though it is possible, and even likely, that bats began roosting in the Houghton Road UPRR bridge shortly following its construction in 1962, the presence of bats at the bridge was not documented until May 1998 (AGFD Heritage Management System Database 2010). Four species of bats were confirmed to use the bridge through captures during the summers of 1998 and 1999: the Mexican free-tailed bat (Tadarida brasiliensis), the cave myotis (Myotis velifer), the big brown bat (Eptesicus fuscus), and the pallid bat (Antrozous pallidus) (Wolf and Shaw 2002; Sandy Wolf, biologist, unpublished data). Use of the bridge as a maternity roost site was first confirmed in 1998 for pallid bats and was suspected, but not confirmed, for Mexican free-tailed bats (Sandy Wolf, biologist, unpublished data). Monthly surveys of the bat population at the bridge conducted from January through December 1999 (Table II-1) document that bats used the bridge year-round (Wolf and Shaw 2002). Numbers for Mexican free-tailed bats represent the minimum number of bats present (bats counted in crevices by visual observation). Visual observation was assisted by the use of spotlights and binoculars. This method cannot account fully for the depth or density of individuals in the crevices, thus numbers may be underestimated. Table II-1. Monthly daytime survey results for the Houghton Road UPRR bridge, 1999 Bat Species Survey Date Mexican Free-tailed Bat (Tadarida brasiliensis) Cave Myotis (Myotis velifer) Big Brown Bat (Eptesicus fuscus) Pallid Bat (Antrozous pallidus) January February March April May 8 1, June 15 1, July August 12 1, September 14 2, October 11 2, November December A + after the number of bats indicates that there are likely more bats present than could be counted Source: Wolf and Shaw 2002 Because bat use at a bridge can change over time, EcoPlan Associates, Inc., conducted surveys at the bridge from July through December 2011 (Table II-2). All four species continue to occupy the bridge, and use of the bridge as a maternity site was confirmed for pallid bats, big brown bats, and Mexican free-tailed bats. The predominant use of the bridge continues to be by the Proposal for RTA Wildlife Linkages Funding 19 Houghton Road Widening at Union Pacific Railroad

23 Mexican free-tailed bat. Their 2011 observed numbers were substantially higher than the 1999 results. Numbers of the cave myotis, big brown bat, and pallid bat remain statistically in the same order of magnitude as the 1999 survey results. Table II-2. Daytime survey results for the Houghton Road UPRR bridge, 2011 Bat Species Survey Date Mexican Free-tailed Bat (Tadarida brasiliensis) Cave Myotis (Myotis velifer) Big Brown Bat (Eptesicus fuscus) Pallid Bat (Antrozous pallidus) July * July 8 2, * July 18 (hundreds) * 1 20 * 47 * July 26 1, August August 16 3, September 13 4, October 5 4, December 27 1, Source: Sandy Wolf, biologist, Houghton Road Bridge Survey 2011 * Young were observed A. Pallid Bat In Arizona, the pallid bat ranges statewide in the summer and in the southern half of the state in the winter (AGFD 2002a) but is present at the Houghton Road UPRR bridge only from April through October (though one individual was noted in November and December 1999) (Wolf and Shaw 2002). Though they occupy man-made structures such as old buildings and bridges in addition to natural roosts in cliff crevices and rocky outcrops, they do not inhabit highly urbanized areas in southern Arizona (Wolf and Shaw 2002). The Houghton Road UPRR bridge was the only bridge occupied by pallid bats of the 43 bridges surveyed by Wolf and Shaw in All the bridges in their study provided vertical crevices and were in the Tucson metropolitan area and adjacent outlying areas. The pallid bat s diet, foraging style, and small home range may limit this species to roost in or near large areas of natural desert. The pallid bat prefers large insects, most often taking prey from the ground. Pallid bats begin to appear at the Houghton Bridge in April, increase in numbers in June through August, and then decrease as bats leave the bridge through October. The colony is a maternity colony of adult females and young. Of 65 pallid bats captured in 1998 and 1999, only two were adult males (Wolf and Shaw 2002). This is not unusual, as male and female pallid bats commonly roost separately in the summer (Hall 1946, Beck and Rudd 1960, Vaughn and O Shea 1976, O Shea and Vaughn 1977). The colony returns each year to give birth and raise their young; female young of the year typically return the next year to give birth. Pallid bats can live at least 9 years (AGFD 2002a). Females give birth to one or two young (Harvey et al. 1999); the colony at the bridge gave birth about the third week in June in 1998 and 1999 (Wolf and Shaw 2002). Young were observed at the July 2, 2011, survey. The maximum number of pallid bats observed was 81 in 1999 (Wolf and Shaw 2002) and 40 in The decrease may reflect a real change in colony size. Though pallid bats usually roost Proposal for RTA Wildlife Linkages Funding 20 Houghton Road Widening at Union Pacific Railroad

24 together in several areas of the bridge, Mexican free-tailed bats often roost with them. Obtaining an accurate count of bats packed in closely together is difficult because the bats are often in more than one layer in the crevice; individuals above the lower layer cannot be seen. However, survey methods and the surveyor were the same for past and present surveys, so it is possible that numbers have decreased somewhat over the years. With one exception, pallid bats have been observed at this bridge only at the ends of the beams near or at the piers. Potential reasons the bats prefer these particular places include temperatures possibly being slightly more moderated than center areas of the span, the piers providing a horizontal roosting place, and the crevice areas possibly being slightly wider. Crevice areas occupied by pallid bats were among the widest available in the bridge. Bats roosted in the spans of the bridge near its ends (but not at the abutments), possibly due to their distance from disturbance caused by passing trains. B. Big Brown Bat In Arizona, the big brown bat ranges statewide in summer and in the southern half of the state in winter (AGFD 2004a). In Tucson area bridges, big brown bats were observed only between May and October, increasing steadily in numbers through September and dropping sharply in October (Wolf and Shaw 2002). This is a common species that often ranges into cities and other areas where humans are present. The species roosts in man-made structures such as attics, barns, bridges, and mines (Harvey et al. 1999, AGFD 2004a). Though Keeley and Tuttle (1999), who surveyed bridges for bats throughout much of the United States, found that this was the second most commonly observed species in their surveys of bridges, big brown bats were found in surprisingly few bridges in the Tucson area (Wolf and Shaw 2002). The Houghton Road UPRR bridge supported the secondlargest number of big brown bats among the bridges surveyed by Wolf and Shaw (2002) in the Tucson area. In 1998 and 1999, big brown bats were only detected in the Houghton Bridge during August (68), September (88), and October (2), suggesting that the bridge was used as a transitory or late-summer roost site (Wolf and Shaw 2002). However, a maternity colony (adults with young) was observed in the Houghton Bridge in July 2011 (bats probably arrived in May before surveys started in July). Continued use as a late-summer roost was confirmed in 2011 (Table II-2). Big brown bats have been known to live for at least 19 years in the wild (Nowak 1995). Females show a high degree of site fidelity, returning to the same roost year after year to give birth (AGFD 2004a). Bats in the western United States usually have only one young each year (Harvey et al. 1999). Parturition occurred in big brown bat maternity colonies in Tucson bridges from late June through mid-july in 1998 and 1999 (Wolf and Shaw 2002). From observations at Houghton Bridge in 2011, birth appeared to occur in early July. Though maternity colonies of big brown bats are common residents in Tucson carports and porches, the addition of the Houghton Road UPRR bridge brings the total known bridge maternity sites in the Tucson area to six (Wolf and Shaw 2002). Big brown bat maternity colonies in Tucson prefer rather wide bridge crevices (0.8 inch to 1.8 inches). Wide bridge crevices are not as prevalent in Tucson bridges as narrower crevices (Wolf and Shaw 2002); however, the most likely reason for few bridge roosts is that high summer temperatures and low Proposal for RTA Wildlife Linkages Funding 21 Houghton Road Widening at Union Pacific Railroad

25 humidity within bridge crevices closely approach the tolerance limits of the species (Wolf and Shaw 2002). Big brown bats, a temperate species, are less tolerant of high temperatures than other species such as the subtropical Mexican free-tailed bat. The largest maternity roosts in Tucson bridges were in the bridges, or parts of bridges, with the most overburden; temperatures were more stable with cooler temperatures during the hot part of the day (Wolf and Shaw 2002). Bridges in Tucson, including the Houghton Road UPRR bridge, are likely too hot in summer for male big brown bats, which typically do not roost with maternity colonies but choose cooler locations or altitudes (Easterla 1973) and were rarely observed in Tucson bridges during maternity season (Wolf and Shaw 2002). Decreasing daytime high temperatures within Tucson bridge roosts in late August through September may also serve to explain why numbers of big brown bats in bridge roosts increase during that period (Wolf and Shaw 2002); crevice temperatures become suitable for males as well as females and young of the year moving through the area. Though the relative significance of bridge roosts in Tucson compared with other man-made structures in the area may be small, maternity colonies that roost in buildings in close proximity to people are frequently excluded and forced to find alternate sites (Sandy Wolf, biologist, personal observation). As a result of exclusion, reproduction can be negatively affected (Brigham and Fenton 1986) and can influence long-term population dynamics. Bridges, particularly ones in outlying areas such as the Houghton Road UPRR bridge, can serve as a permanent refuge, and help keep this common species common. C. Cave Myotis In Arizona, cave myotis are primarily found south of the Mogollon Plateau in the spring through fall; small numbers have been found hibernating in winter (AGFD 2002b). These bats roost in caves and mines but also use old buildings and bridges (AGFD 2002b). Keeley and Tuttle (1999) observed that the cave myotis was the third most commonly observed species of bat roosting on bridges in the southern and western United States and noted large maternity colonies in their surveys. In the Tucson area, cave myotis are present from April to October. Males and females use bridges as migratory stopover sites in the spring and fall, but few bats are present in the hottest months of summer (Wolf and Shaw 2002). Occupied bridges are in outlying areas adjacent to undeveloped land (Wolf and Shaw 2002). The Houghton Road UPRR bridge had the highest number of cave myotis observed in bridges in the Tucson area in 1999 (Wolf and Shaw 2002). Wolf and Shaw (2002) noted that numbers of cave myotis at the bridge were probably higher than recorded because of the bats habit of roosting among the more numerous Mexican free-tailed bats and because of the difficulty of distinguishing species due to the height of the bridge and narrow crevices. In addition, the length of time an individual bat stays at a particular roost while migrating is unknown, so it is possible that the Houghton Road UPRR bridge supports hundreds or thousands of cave myotis each year as they travel through the area. D. Mexican Free-tailed Bat In Arizona, Mexican free-tailed bats range statewide in summer and over much of southern Arizona in winter, though in diminished numbers (AGFD 2004b). Mexican free-tailed bats are the most commonly observed species roosting in bridges in the southern United States (Keeley and Tuttle 1999) and are the most frequently seen and widespread species observed during the Proposal for RTA Wildlife Linkages Funding 22 Houghton Road Widening at Union Pacific Railroad

26 Wolf and Shaw (2002) surveys of bridges in the Tucson area in Mexican free-tailed bats are the most abundant species present at the Houghton Road UPRR bridge (Table 1, Table 2) and are the fourth-largest number of this species observed among bridges surveyed in the Tucson area (Wolf and Shaw 2002). It is important to note that because this species roosts in large groups of densely packed animals often in layers in crevices numbers reported are estimates of the minimum numbers present for both 1999 and 2011 surveys (Wolf and Shaw 2002). Actual numbers may be twice the number reported. In 1999, surveys determined that Mexican free-tailed bats were present all year, with the highest numbers observed in September and October and the lowest numbers observed in April, November, and December. Despite year-round presence, no evidence of a maternity colony was observed (Wolf and Shaw 2002). Surveys in 2011 showed somewhat higher numbers in summer months than in 1999 and also confirmed that the bridge is used as a maternity roost site. This species gives birth to one young each year; birth occurred in 2011 at the Houghton Bridge in early to mid-july. Wolf and Shaw (2002) speculate that two populations use the Houghton Bridge (as well as other Tucson bridges), one in summer and one in winter, in addition to some transitory bats during migration season. The total number of Mexican free-tailed bats using the Houghton Bridge each year is many thousands. E. Literature Cited AGFD. 2002a. Pallid bat (Antrozous pallidus). Unpublished abstract compiled and edited by the Heritage Data Management System. AGFD, Phoenix, Arizona b. Cave myotis (Myotis velifer). Unpublished abstract compiled and edited by the Heritage Data Management System. AGFD, Phoenix, Arizona a. Big brown bat (Eptesicus fuscus). Unpublished abstract compiled and edited by the Heritage Data Management System. AGFD, Phoenix, Arizona b. Mexican free-tailed bat (Tadarida brasiliensis). Unpublished abstract compiled and edited by the Heritage Data Management System. AGFD, Phoenix, Arizona. AGFD Heritage Management System Database Data sheet for bat colony at the Houghton Road UPRR bridge. Beck, A.J., and R.L. Rudd Nursery colonies in the pallid bat. Journal of Mammalogy 41: Brigham, R.M., and M.B. Fenton The influence of roost closure on the roosting and foraging behavior of Eptesicus fuscus (Chiroptera: Vespertilionidae). Canadian Journal of Zoology 64: Easterla, D.A Ecology of the 18 species of Chiroptera at Big Bend National Park, Texas. Northwest Missouri State University Studies. 34: Hall, E.R Mammals of Nevada. University of California Press, Berkeley, California. Proposal for RTA Wildlife Linkages Funding 23 Houghton Road Widening at Union Pacific Railroad

27 Keeley, B.W., and M.D. Tuttle Bats in American bridges. Bat Conservation International. Resource Publication No. 4. Nowak, G.M Walker s bat of the world. The John Hopkins University Press. Baltimore, Maryland. O Shea, T.J., and T.A. Vaughn Nocturnal and seasonal activities of the pallid bat, Antrozous pallidus. Journal of Mammalogy 58: Vaughn, T.A., and T.J. O Shea Roosting ecology of the Pallid bat Antrozous pallidus. Journal of Mammalogy 57: Wolf, S.A., and W.W. Shaw Roost selection of bridges by bats in an urban area. AGFD Heritage Grant (U98007), Final Report. Proposal for RTA Wildlife Linkages Funding 24 Houghton Road Widening at Union Pacific Railroad

28 III. DESCRIPTION OF PROPOSED BRIDGES The proposed new overpass structures consist of two three-span structures separated by a 16-foot-10-inch open median. The total bridge length is just more than 348 feet, with the northbound bridge 59 feet 10 inches wide and the southbound bridge 53 feet 10 inches wide. Bridge span length and pier locations would be designed to maintain the necessary space for the utilities and maintenance access roads on both sides of the tracks, within the UPRR right-of-way. Consistent with the existing bridge, the proposed bridge is skewed just more than 33 degrees east of north. The new structure will have a longer and gentler crest curvature than the existing structure, increasing the sight distances to improve traffic safety. The height of the bottom of the structure above the railroad tracks will be more than 23 feet 3.28 feet less than the current height. The height of the end spans will vary from about 24 feet on the south end to about 16 feet on the north end. The new bridges would consist of an asphalt roadway on a concrete bridge deck (varying in thickness between 8 to 9.5 inches) supported by American Association of State Highway and Transportation Officials Type VI Modified Girders (7 feet high) on 4-foot-diameter reinforced concrete columns with concrete pier caps. The bridge abutments will tie into earthen approach embankments. See Figure III-1 for the proposed bridge plan and profile. Construction of the new northbound bridge will take place first while leaving the old bridge in place to continue to accommodate traffic flow. Once the new northbound bridge is complete, traffic will be rerouted to the new bridge, and the old bridge will be demolished. Construction of the southbound bridge will start once the old bridge is completely removed. Proposal for RTA Wildlife Linkages Funding 25 Houghton Road Widening at Union Pacific Railroad

29 Proposal for RTA Wildlife Linkages Funding 26 Houghton Road Widening at Union Pacific Railroad

30 IV. MITIGATION PLAN A. Mitigation Planning It is important that engineers and biologists engage in a cooperative planning process well in advance of construction to develop an ecologically effective, cost-effective, and structurally satisfactory mitigation process for the successful relocation of bats during this bridgereplacement project. Such planning will include the timing of exclusion to coincide with the biological and roosting cycles of bats to reduce the stress to the bat population and to increase the success of relocation. Artificial roost designs have been discussed as well as alternative locations on the new bridge to avoid causing structural problems or interference with the maintenance and inspection of the bridge. Recommendations from biologists, including bat experts, for components critical to successful mitigation have been incorporated into plans and will be implemented. These recommendations are a result of lessons learned after the failure of several bridge and bat projects in California (Johnston et al. 2004). Potential planning and coordination issues for roost habitat installation, exclusion of bats, and the timeline for activities for the Houghton Road UPRR bridge project include: Permissions to access the UPRR right-of-way Biologists and engineers need to coordinate project construction timelines and mitigation timelines Exactly where roost structures are allowed to be installed on the new bridge to avoid utilities Limitations on roost structure designs and locations to allow for bridge inspection and maintenance B. General Timeline Construction of the new Houghton Road UPRR bridge is tentatively planned for and will begin with the northbound (eastern) half of the bridge, located immediately east of the existing bridge. Following the rerouting of traffic along Houghton Road to the new portion of the bridge, the existing bridge will be torn down and the southbound half constructed. The following key items will be considered in the construction timeline: Preconstruction and During Construction of New Northbound Bridge Obtain permissions from the UPRR for work in the right-of-way Design prototype habitat structures with engineers, get potential structure placement approved Fabricate and install prototype habitat structures in existing bridge, monitor for up to one year to gauge bat use When bats begin to use the prototype habitat structures, test the exclusion techniques by partially excluding bats from occupied crevices in the existing bridge to determine the effect on bats and allow an accurate time estimate for exclusion and sealing of the rest of the bridge Monitor bat use of existing bridge crevices and prototype habitat structures monthly until existing bridge demolition Proposal for RTA Wildlife Linkages Funding 27 Houghton Road Widening at Union Pacific Railroad

31 Monitor temperatures of the Houghton Road UPRR bridge decks, the prototype habitat structures and crevices in the existing bridge, and the Kolb Road bridge over Interstate 10 (similar structurally to the new Houghton Road UPRR bridge) Modify prototype habitat structures as needed to re-create temperature profiles in existing crevices, especially if bats are not using prototype habitat structures Post-construction of New Northbound Bridge Install habitat structures on the new northbound bridge Move habitat structures from the existing bridge to the northbound bridge Exclude bats and seal crevices on the existing bridge in March or November, whichever is sooner Inspect seals on existing bridge periodically for breaks, and re-exclude and repair if necessary until demolition Monitor habitat structures on the new northbound bridge for bat use after construction is complete Monitor temperatures in habitat structures on the new northbound bridge Modify habitat structures depending on demolition schedule Post-construction of New Southbound Bridge Install habitat structures, if needed, to increase crevice space available and, therefore, capacity to accommodate bats Monitor habitat structures on the new southbound bridge for bat use monthly for 1 year after construction is complete C. Location of Roost Structures in the New Bridge The location of structures in the new bridge cannot be determined until biologists and engineers meet, and the location of utilities and other obstacles are identified. Because of the differences in thermal mass and insulation between roosts in the existing bridge and structures in the new bridge, biologists cannot predict where certain species or types of colonies will prefer to roost in the new bridge (e.g., near the sides vs. in the center). For example, because pallid bats currently roost near the sides of the bridge at the ends of the spans does not mean all pallid-size crevices should be near the sides of the new bridge. Structures of various widths, thermal mass, and insulation must be placed throughout all available areas. If possible (given constraints on available locations), structures can be located using a design that can be statistically analyzed to determine which characteristics contribute to a structure s use by bats. Valuable information was obtained by analyzing such data at a bridge in California (Pierson et al. 1996). Additionally, thermal conditions of the Kolb Road UPRR bridge, a bridge similar in structure and construction materials to the new Houghton Road UPRR bridge, will be analyzed to aid in the design and/or the placement of structures on the new bridge. Proposal for RTA Wildlife Linkages Funding 28 Houghton Road Widening at Union Pacific Railroad

32 D. General Designs for Prototype Habitat Structures i. Maberry Bridge Condo This habitat structure measures 26 1/2" in height, 20 1/4" in width, and 38" in length. It has an approximate weight of 210 pounds and is designed for a capacity of up to 2,000 individual bats depending on species. The box itself is constructed of galvanized steel, PVC plastic, stainless steel rivets and stucco on the inside, and cadmium plated hardware on the outside. The roosting area is made of seven individual smaller bat boxes lined with polypropylene black webbing which provides 728 feet in usable surface area. Louvered vents on the sides of the box and space in the top of the structure provide air circulation. Figure IV-1. Maberry Bridge Condo. Photo by Maberry Centre Bat Homes. ii. Concrete Panels Attached to the Vertical Sides of the I-beams Concrete panels of varying lengths will be installed (at least 6 feet long; the longer, the better) with both ends capped entirely, 24 inches high (to allow I-beam to serve as a landing pad), and 2 to 4-plus inches thick. The top will be 2 to 4 inches thick and extend 0.5 to 1.75 inches out from the panel this creates the crevice when attached to the I-beam. To accommodate bats which prefer differing crevice sizes, individual panels can have different widths (0.5, 0.75, 1, 1.25, 1.5, or 1.75 inches) or the panels can be formed so that each panel varies in width to a half-inch wider for shorter panels and 0.75 inch wider for long panels. Most panels will be 0.75 to 1.25 inches wide. Each panel will have a small ledge (for adults to stash their nonvolant young) cut out near the top that is 2 inches high and 1 inch wide, with the bottom sloping down about 15 degrees so that guano rolls off. Sides of the I-beam and the inside of the panel will be rough so bats can grip it easily. Panels can be attached with bolts to the side of the I-beam near its upper vertical surface and to bridge piers. Proposal for RTA Wildlife Linkages Funding 29 Houghton Road Widening at Union Pacific Railroad

33 In the concrete panels, the bats roost in the crevice between the 6-inch-thick I-beam and the panel. There is more thermal mass on the sides of the structure, and perhaps more thermal moderation, than in the other styles of constructed bat roosts. The shape of the I-beam will preclude seeing directly up into the crevice of this structure from the ground; therefore a camera on a pole with a light will be required for daytime surveys. An example of a concrete slab can be seen in Figure IV-2. Figure IV-2. Concrete roost panel attached to bridge beam (Johnston et al. 2004). Staining is evidence of bat use. Photo by Greg Tatarian. iii. Texas Bat Abodes Modified for the Tucson Climate Though plywood structures are apparently successful in Texas, Tucson s summer temperatures preclude the use of wood, a material with insufficient thermal mass. The modified bat abode consists of a box constructed of an insulated steel shell (similar to the Maberry bridge condo), with crevices formed from panels of Durock (or similar material). This design provides both thermal mass and insulation, which is necessary during periods of temperature extremes. Crevices would be 24 inches deep; length and width of the box would vary depending on the amount of insulation and layers of Durock. Many smaller boxes (fewer crevices) may be more feasible due to weight than fewer larger ones. Crevice widths should vary from 0.75 to 1.75 inches, with most between 0.75 and 1.25 inches. This structure would hang from bolts attached to the underside of the bridge deck. E. Literature Cited Johnston D., G. Tatarian, and E. Pierson California bat mitigation, techniques, solutions, and effectiveness. Prepared for the California Department of Transportation and California State University Sacramento Foundation. Sacramento, California. Proposal for RTA Wildlife Linkages Funding 30 Houghton Road Widening at Union Pacific Railroad