The dam functioned satisfactorily thi-oiighout the spring of 19pl..> blocked 

 all laiiipreys entering the stream from reaching the spawning groxmds in 

 that river J and, offered no significant barrier to the \ipstream migra- 

 tions of game fishes. 



Control structures of this type vrl.ll be especially usefxtL in many 

 streams on the southwestern shore of Lal:e Superior indaich ax's cha:;'acter- 

 ized by steep gradients and very stable substrata and -where poor access- 

 ibility precludes the installation of devices which must be serviced 

 daily. 



Portable-type iveirs and traps. — S'^reen, trap, and bracirig units of 

 the several portable-type weirs were operated in the streams of Control 

 Zone H-1 and in Lal-ce Superior tributa;:;'ies in 19^1 ivith no major structural 

 changes. Wearing quality of the original units, as designed, has been 

 found to be excellent. Most portable-t;rpe screen and trap units appai'- 

 ently will give from I4. to 5 years of service under reasonable stream con- 

 ditions before any replacement becomei:- necessary. 



One innovation tested in Carp Creek, Presque Isle Co-ant}'', Mich,, was 

 the use of permanent sills, trap base, aizd abutments which were con- 

 structed of reinforced concrete (figs. 5 and 6). This stable substruc- 

 ture proved extremely effective. It pL'actically eliminatec' danger of 

 undercutting or bank-cutting and provided continuous troubld-free opera- 

 tion through a spring season of unusually high floods. 



Similar concrete sills and abutments were installed in Hibbarda 

 Creek, Door County, Wis., by the Wiscor.sin Conservation Department. This 

 installation likewise proved to be much more effective than the wooden 

 substructures used in previous yearr. 



The specific advantages of these v:;oncrete substinictui-es appear to 

 be as follows: (1) elimination of occasional replacement of substruc- 

 tm-'e; (2) reduction of maintenance of substructure to a minim-om,; (3) 

 reduction of wear on portable screen .and trap units j and, (u) reduction 

 of operating costs through increased e.ose of -weir operation (fe-#ei' man- 

 hours required for inspection and servicing). It would, seem, advisable, 

 therefore, in a long-term control program to install this mo:."e stable 

 weir and trap base in all streams where the portable-type str^ictu;.-es sz'e 

 to be used. Although initial capital outlay vrould obviously be g:?eater 

 tlian for similar wood substructiireE, tie advantages indiuatsd above 

 should effect more than compensating cr/ings over a period of years. 



Operating costs in 1950 and 19^1 fo"-£ Control Zone H-1 and one stream 

 tributary to Lal-:e Superior. — Detailed records have been kept tlii'ough two 

 seasons of~operations of the costs ino--:.rred in installing^, operating, and 

 maintaining the 12 weirs and traps of Control Zone H-1 and the Pendills 

 Creek iveir. Briefly, these 13 conti-ol .structures were installed at an 

 aggregate cost of $17,95U and operated, successfully during the 19^0 sea- 

 son for $8,698. They vrere reinstalled in 19^1 at a cost of ^2,350 and 

 operated throughout that season for $7,35l. The cost of reinstallation 

 in 1951 is not typical of a normal season since it includes fi,mds expended 



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