Review of Culvert Suitability at La Platte Bottoms Highway Project

The following are replies were received from the Nebraska Department of Roads and U.S. Fish and Wildlife Service in response to specific inquiries regarding culverts to be constructed in association with the pending construction at the La Platte Bottoms. As both are public agencies, their replies are given here, and presented verbatim, so that anyone else interested in the situations regarding this project can be informed of their response. A notice indicating that any reply would be posted online was also included with the email sent to the NDOR.

Nebraska Department of Roads Response

"The following is a list of culvert structures being constructed as part of the U.S. 34 Missouri River Bridge project that occur within the area that you have identified as the 'La Platte Bottoms.'

• "At project Station 174+24, a 36 in culvert pipe will be constructed to connect the delineated wetland area south of the new Highway 34 to the ag ground north of the new Highway 34 embankment. This culvert is listed as note no. 102 on the attached plan view sheets.
• "At Project Station 188+50, 2-24 inch culvert pipes will be constructed through the new Highway 34 embankment west of the new Harlan Lewis road intersection with Highway 34. This culvert is listed as note no. 103 on the attached plan view sheets.
• "At Project Station 204+16, a twin 6 ft. X 4 ft. concrete box culvert will be constructed through the new Highway 34 embankment connecting delineated wetlands occurring on both sides of the new Highway 34 embankment. This culvert is listed as note no. 104 on the attached plan view sheets.
• "At Project Station 210+55, a 6 ft. X 4 ft. concrete box culvert will be constructed through the new Highway 34 embankment connecting delineated wetlands occurring on both sides of the new Highway 34 embankment. This culvert is listed as note no. 105 on the attached plan view sheets.
• "At Project Station 3210+20 (new La Platte Road East alignment), a 6 ft. X 4 ft. concrete box culvert will be constructed through the new La Platte Road East embankment connecting delineated wetlands occurring on both sides of the new La Platte Road East embankment. This culvert is listed as note no. 108 on the attached plan view sheets.
• "At Project Station 3224+42 (new La Platte Road East alignment), 2-30 inch culvert pipes will be constructed through the new La Platte Road East embankment connecting delineated wetlands occurring on both sides of the new La Platte Road East embankment. This culvert is listed as note no. 109 on the attached plan view sheets.

"Beyond the culverts listed above, there are several other 24 inch culverts used for driveways and at roadway intersections that are placed to convey roadside ditch drainage flows. These culverts would aid in the overall surface water connection within the La Platte bottoms and provide some opportunity for semi-aquatic species to cross through the ancillary roadway embankments.

Fish and Wildlife Service Reply

"Thank you for your interest in wildlife crossings. In Nebraska, we provide general recommendations to facilitate the passage of fish and wildlife species for proposed structures that are to be placed in waterways. We advocate that structures are designed to retain the natural gradient, substrate, and width of stream courses. These recommendations are also included:

• "Incorporate rigorous soil erosion control practices both during and after the proposed construction, including temporary construction activities or any other alignment procedures in order to avoid impacts to fish and other aquatic organisms.
• "Do not alter or install culverts in any way that would result in reductions in current channel width.
• "Structure(s) should be designed appropriately for both terrestrial/aquatic passage as well as for the movement of water.
• "The placement of the structure(s) should be at appropriate elevations so as to not impede terrestrial/aquatic movement.

"Transportation impacts to landscape permeability and the need to assess impacts to and mitigate for wildlife connectivity has been gaining worldwide attention. Wildlife crossings have been incorporated into transportation planning and are designed to reduce wildlife mortality, improve habitat connectivity, and reduce vehicle collisions.

"During the review of the Bellevue Bridge Project, we were unaware of: safety concerns for any federally listed species or the traveling public, observed mass mortalities of any species, low population survival probability for specific species, or public interest/concerns for specific needs for wildlife at the La Platte Bottoms location—all items that would necessitate specific crossing mitigation for a targeted species. However, general mitigation approaches were taken to avoid, minimize, and compensate for permanent habitat impacts for the overall project impacts.

"After a review of proposed culverts for the La Platte Bottoms area provided by the Nebraska Department of Roads (NDOR) on July 28, 2010, we understand that these structures are not functioning as stream crossings, but are being placed to manage and route roadway run-off along, under, and away from the roadway (i.e. cross-drains). It appears from the July 28 culvert information, culvert pipes range in diameter size from 24 inches to 36 inches, and box culverts are sized at 6 feet x 4 feet, (some multi-chambered). For the location, it appears that the distance between structures (observing station numbering) ranges from approximately 5 to 140 feet (total structures = 10). Additionally, the cross-sections provided for the proposed culverts show that the structures will be constructed at or just below the existing ground elevation.

"Numerous species use culverts and concrete box structures, including mice, shrews, foxes, rabbits, river otters, opossums, raccoons, ground squirrels, skunks, coyotes, bobcats, great blue heron, long tailed weasel, and herps (Yanes, et. al. 1995; Brudin III, 2003; Dodd et. al., 2004; Ng et. al. 2004). For small mammals, pipe culverts ranging from approximately 12 to 48 inches in diameter have been found preferable (Clevenger et. al. 2001; McDonald & St Clair 2004; Ruediger & DiGiorgio 2007). Since most of these species also have small home ranges, metal or cement box culverts should be installed at intervals approximately 150-300 meters (Clevenger et. al., 2001). Inadequately sized crossings, insufficient number of crossings, and culvert design are primary causes of poor use by wildlife (Ruediger 2001; Clevenger et. al., 2001).

"We have determined that these proposed structures will be adequate based on our general recommendations and what has been observed in the literature. However, we will monitor the site in the future.

"Thanks again for your interest in this project.

"References

"Brudin III, C.O. 2003. Wildlife use of existing culverts and bridges in north central Pennsylvania. ICOET 2003.

"Yanes, M., J.M. Velasco, and F. Suárez. 1995. Permeability of roads and railways to vertebrates: the importance of culverts. Biological Conservation 71: 217-222.

"Dodd, C.K, W.J. Barichivich, and L.L. Smith. 2004. Effectiveness of a barrier wall and culverts in reducing wildlife mortality on a heavily traveled highway in Florida. Biological Conservation 118: 619-631.

"Ng, S.J., J.W. Dole, R.M. Sauvajot, S.P.D. Riley, and T.J. Valone. 2004. Use of highway undercrossings by wildlife in southern California. Biological Conservation 115:499-507.

"Clevenger, A.P., B. Chruszcz, and K. Gunson. 2001. Drainage culverts as habitat linkages and factors affecting passage by mammals. Journal of Applied Ecology 38: 1340-1349.

"McDonald, W., and C.C. St Clair. 2004. Elements that promote highway crossing structure use by small mammals in Banff National Park. Journal of Applied Ecology 41 82-93.

"Ruediger, B. and M. DiGiorgio. 2007. Safe passage: a user’s guide to developing effective highway crossings for carnivores and other wildlife. USDA Forest Service, Federal Highway Administration, Wilburforce and Southern Rockies Ecosystem Project. 19 pgs."