INSIDE TEMPE:  A Special Report

BY: Dmstrang

TEMPE  (October 15))  According to the Tempe Republic, Tempe is considering four options for replacement of the rubber dam on the west side  of the Tempe’s Town Lake.

Dam It

We have learned that there is a fifth option: “The replacement dam could well be a Beaver Dam.” That is the opinion of an un-named city staffer who prefers to remain anonymous because the Mayor and City Council have yet to make a final decision.

“However,” the staffer says, “the decision to build a Beaver Dam seems obvious.” The research to decide the best alternative to replace the current rubber bladder dam has been narrowed down to a few alternatives: an earthen dam, a concrete dam, some sort of metal construction or….a Beaver Dam. The cost for any of these alternatives has yet to be determined. But, early speculation indicates that a Beaver Dam would be the most cost effective and environmentally sound solution.

City of Tempe staff responsible for the project are currently calculating how many beavers it would take to construct the dam, where the trees and material would come from needed to replace the dam, and how the dam could be maintained by the beavers who would work in conjunction with SRP, the agency that manages the dam’s water flow.

One SRP official said, “If we had thought about beaver technology back in 1910, we might have been able to build Roosevelt Dam for a lot less money. But then we would have had to figure out what to name the dam in the absence of President Roosevelt.”

One of the challenges for the beaver option is that the Town Lake dam would be the largest ever constructed by beavers. The biggest beaver dam known is 40 feet long by 10 feet high, and required 17-21 beavers to make it happen Given the size of the Town Lake dam the city is estimating how many beavers it would have to contract with for the project so that it meets it’s targeted completion deadline.

Another issue to be resolved is the availability of construction materials. It is believed that the city could work with state forestry officials to employ a certain number of beavers who would gnaw down trees from forests in the northern sections of Arizona, especially those areas that need tree thinning to prevent future forest fires. Those trees would then be shipped to Town Lake shores for use in dam construction.

City planners concede that estimates of the number of trees needed for dam construction are, at this point, anyone’s guess. It is also possible that a number of beavers could be employed to explore the river bottom west of the lake to find materials that might be used and, in the process, improve the Salt River’s habitat.

Replacement Alternative

There are hurdles in the way of making a final decision: the dam must contain the lake at consistent levels, and it must provide a means to open the dam for the times SRP needs to release excess water down the Salt River.

Planners believe the Beaver Dam could be managed to meet both requirements.

The dam would be constructed to permit a small trickle. Unlike a concrete, steel, rubber or earthen dam, a Beaver Dam would have natural openings through which water can flow. SRP and Tempe would work closely with a cadre of beavers, who will remain employed after construction, to open and close small sections of the dam to regulate water flow. Beavers often construct lodges as part of the dams they build in which they also raise their children (kits). The city envisions that beaver lodge condos would easily house those needed for dam maintenance.

In the event of a large water release, these same beavers could quickly take down a significant portion of the dam to permit major flows. When the water flow was no longer necessary, the beavers would simply restore the dam.

Planners are also evaluating whether or not specially trained beaver wranglers might be required to coordinate construction and maintenance in order to facilitate communication between the beavers, the city and SRP.  Arizona State University is exploring the possibility of creating a beaver wrangler degree.

Officials noted that there is at least one strong advantage to the Beaver Dam option: it would keep a large number of beavers employed for an extended period of time. In anticipation of this opportunity some Mill Avenue merchants are already contemplating the opening of beaver oriented yogurt shops.

In addition, The Tempe Tourism Office is working with Tempe hotels to offer special weekend beaver observation packages; and Ironman executives said that having beavers swimming with and next to Ironman contestants would certainly offer support and encouragement to the swimmers.

(For additional information about beavers, go to www.globio.org or www.fcps.edu