19 



Figure 7. — ^Plan of catch basin 



wooden frame which fits into the slots. The screen may- 

 be as fine as 8 meshes to the inch or as coarse as 4 to 

 the inch, depending on the use to which it will be put. 



The second slots are for dam-boards or stop-logs. 

 These are usually made of 2- by 8- or 10-inch treated, 

 finished lumber, and beveled on either end to fit. The 

 boards are placed one over the other up to the desired 

 water level in the pond, and they serve as an overflow 

 where rainfall or other water may raise the pond above 

 the desired level. These boards may be kept tight by 

 small wedges inserted at either end of the upper board. 

 Sometimes mulch or wet sawdust is thrown In front if 

 there is considerable seepage around the boards. 



An alternative type of cons truct ion ,i s a solid 

 concrete wall 18 to 20 inches ahead of the outlet in 

 the outlet box to the height of the water level and 

 about 10 inches below the top of the chimney. In the 

 bottom of the wall is an opening opposite the outlet 

 provided with an irrigation gate or a homemade gate as 

 shown in fi gure 8. The chimney should be provided with 

 slots for a screen. 



