Table of Contents Executive Summary 2
Consequences of Amphibian Loss
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- Amphibians and Culverts
- Culvert Replacement/Upgrade Costs
Consequences of Amphibian LossThe loss of amphibian species, through numerous mechanisms, has far-ranging implications for ecological food-webs and ecosystem structure. Amphibian diet consists primarily of insects, followed by other invertebrates and vertebrates. Amphibians convert invertebrate biomass into a food source more available to higher trophic levels (Cofrin Center for Biodiversity, 2003). Due to very small body size, amphibians are also able to consume prey too small to be accessible to birds and mammals. An individual Blanchard’s cricket frog consumes close to 4800 insects a year(Cofrin Center for Biodiversity, 2003). This, coupled with very low metabolic rates, makes the conversion of insect biomass into amphibian biomass very efficient (Pough et al, 1987). Many amphibian species provide important ecotone interactions by foraging for insects in upland habitats. In some Vermont forests, eastern red-backed salamander (Plethodon cinerus) biomass is greater than birds and small mammals (Cofrin Center for Biodiversity, 2003). The annual biomass production of red-back salamanders in these forests can be greater than that of all birds and mammals (Pough et al, 1987). The importance of amphibians as ecosystem and food-web components stresses the consequences of widespread declines. Amphibians and CulvertsSome types of amphibian crossings have been more successful than others. To keep amphibians from crossing the road, there are a couple of options. Silt fences can be used to deter the amphibian from crossing. They are relatively inexpensive, requiring only wooden stakes, and canvas. However, silt fences are labor intensive and necessitate maintenance. A community group or a Boy Scout troop could provide this upholding. Concrete walls also deter amphibians from crossing the road. Concrete walls are more expensive than silt fences, but require much less maintenance. Box-shaped culverts and round culverts are options for amphibian to cross under a road. The choices of pipes are bituminous-coated corrugated steel, High Density Polythene Pipe, corrugated aluminum pipe, and reinforced concrete pipe. The choice for box culverts is concrete (LWDD, 2003). Vermont is beginning to turn its focus towards protecting amphibians from road mortality. Because there is less human population in Vermont, the roads have different amounts of travel than heavily traveled Florida roads. Therefore different measures should be taken to protect them. VTRANS could be guided by the research done at the University of Massachusetts. At University Of Massachusetts, Scott Jackson has led the way for the study of amphibian culvert research. The variables affecting use are said to be size, placement, moisture, hydrology, temperature, and noise (Jackson, 2000). It is important to consider what amphibians prefer, when crossing under a road. “Relatively small amphibian and reptile tunnels may be a cost effective means of mitigating highway impacts where roads and highways are located between wetlands and upland habitats” (Jackson, 2000). S The substrate of the culvert is important for promoting amphibian crossing. Jackson advocates using sandy soil for the bottom of the culvert as well as providing cover such as tree stumps. Bill Ruediger, the Ecology Program Leader for Highways at the USDA Forest Service’s Washington Office recommends a natural bottom surface such as rock or dirt (Ruediger, 2003). 
Culvert Showing natural substrate and wing walls to guide amphibians under the road.http://www.fhwa.dot.gov/environment/wildlifecrossings/photo25.htm Wing walls are used to funnel the amphibians into the tunnel. The wing walls ought to extend at forty-five degrees to funnel the amphibians toward the culvert. The walls should extend vertically at least eighteen inches. The vertical walls should extend one hundred to two hundred feet outward and the tops of the walls should be parallel with the ground surface on the side closest to the road. Jackson recommends that the crossing structures should be placed less than one hundred feet apart (Jackson, 2000). Comparison of different culvert types is important for Vermont so that the least expensive measure can be used. “There is evidence that amphibian and reptile tunnels are effective when used with two lane roads…. it is not known how effective they will be for facilitating passage beneath highways of four or more lanes” (Langston et al in Jackson, 2000). Ruediger recommends in order of preference, cement box culverts, cement round culverts, PVC pipe, then corrugated steel as the least preferable (Ruediger, 2003). Culvert Replacement/Upgrade CostsRound culverts are less expensive than box shaped culverts, so in the interest of budget; this paper will focus on them. The four types of materials used for pipe culverts are steel, aluminum, and concrete, and HDPE, or High Density Polythene Pipe. Table 11 shows the cost of production and the installation price for two lane roads. The table also shows the budget for VTRANS in 2004. $50,722,184 goes to maintenance, which is where the culvert replacement would take place (Hoffman, 2003). Table 1. The price of different culvert materials and installation.
Dave Lathrop of (??) averages culvert replacement costs between $5,000 - $10,000 dollars. He states that amphibian culverts are closer to $5,000 because they are dug at a small depth. However, the figures depend on many variables such as size and length of culvert, traffic control, and depth of culvert (Lathrop, 2003). Gil Newbury of (???) states that the minimum culvert size used under state highways is 18 inches. Also culverts less than 4 feet in diameter are primarily made of plastic. Gil adds that cost depends not only on depth, but also on the wetness of the site. He expects a cost of between $3,000 and $5,000 (Newbury, 2003). Chris Slesar of VTRANS states that access to a site will affect the cost. He uses the example that if a culvert needs to be installed on a steep slope, then more labor will increase the costs. Other variables he lists are traffic volumes and guard rail presence (Slesar, 2003). Chad Allen of VTRANS says that the material cost of HDPE, CMP, and RCP - (reinforced concrete pipe) are $21.04/LF, $26.12/LF, and $28.00/LF correspondingly. Therefore if a 35 to 40 foot pipe was fitted under a 2 lane road, then the difference in material only comes out to about $150-$200. For a $5,500 job, this is fairly unimportant. Allen also states that the District's first choice is to install HDPE. The other materials such as CMP, are used in areas where the culvert needs to be installed deep within the ground (Allen, 2003). The problems encountered are that price of the pipes depends on how much the consumer will buy. Robert Flint of the Florida Department of Transportation explains that the more bulk of pipe bought, the less expensive it will be. He said “ we may have a price for a 24" pipe (Concrete Pipe) that is 8 ft. long. If the quantity needed is 1,000 ft., then the price is $23.00 per foot” (Flint, 2003). Also, a potential problem is the culvert’s function in a storm event. Chad Allen, District 5 Transportation Program Manager, recommends that the culvert equalize water between wetlands or push water away from the road (Allen, 2003). Download 181.31 Kb. Share with your friends:
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cott Jackson recommends using box culverts over pipes. As for the size, he suggests bigger culverts with a wider diameter. This will be more accessible for animals meaning less mortality. Jackson advises at least two feet by two feet squared at the openings. Open tops that allow light will attract more amphibians. Jackson suggests using concrete. If a pipe is to be used, he also suggests a good standard culvert diameter is fifteen inches (Jackson, 2000).