]84 



lUO'i, tlK' dam was very caivfully coiistnioted of fjood clean clay, with 

 a concrete core carried down into the nx-k far enough to i)revent any 

 likelihood of leakage thnniicli tlie siil)stratniii. As soon as this pond 

 filled, nevertheless, severe leaks developed under the spillway, through 

 the crevices of the lock. as in the case of the old dam. It is thought that 

 some of the wati-r .-iiipcariiig at this leak actually comes from the upper 

 (first) iiond, making the entire journey through the cavernous rock of 

 the vallcy-side. .Vn attciiipl was next nnule to rei)air this leak hy tun- 

 Tieling into tiic valley side at the sjiillway. This excavation developed 

 the fact th.it there is a mnd-filled seam, extending hack into the hill be- 

 tween two layers of limestone. This stvim was followed hack into the hill 

 alMint 40 feet, and as it showed no sign of closing uji. the jiortion excavate<l 

 was filled with concrete, and the attempt at repair was alumdoned. It is 

 altogetliei- likely that the entire hill is c.-ivernuus to an niuisual degree, 

 and that, tiie only w.ny to render the valley side tight would be to expose 

 the rock ■•ilong this entire side of the jiond. and close all of the Joints and 

 seams with concrete. .Vt the jiresent time the entire water supply of 

 I'.loomington is pnniiicd from the leak under the spillway of the lower 

 pond. ;in(l an e(|nal amount is pumped h.-ick into the ponds. That is, the 

 leakage at present amoinits to over a million gallons a day. Both of 

 these iionds are located in the Mitchell limestone, the foundation of the 

 dam of the lower jtond resting on the toji of the orditic limestone. 



lOiKMigh exidiMice lias now been cited to ]iro\"e beyond ;iny question 

 that the general ireologicil conditions in the limestone region .are distinctly 

 nnfavorable to the impounding of water. One cornllary to bi' drawn from 

 this fact is llial all towns witiiin a leasonable distance (a few miles) of 

 the Kiiobstoiie ai'ea. sbonld iilili/.e the latter for their water-snpi>ly sys- 

 tems. Where it is necessary to obtain water, if .-it .all. from the liinestoiK- 

 area, the iioi'tions underlain by tlie Oiililic limestone or the ILarrodsbur!,' 

 limestone shoulil be utilized in iirel'erence |o the area underlain by the 

 .Mil(licll limestone, .iiid the Oiililic is to be pi'el'crred to the llairndsburg 

 Ff it liecomes necess.ary lo nlili/.e the Mitchell .ire.i. the following facts 

 siiould be noted: Fiisl, it will be noticed by any one familiar with tlu» 

 .Mifcjiell Jimeslone Ih.il llieic is a layci' or bed of r.illier impervious rock 

 about r>(> leet ab(i\(' the base of the formation. This layei" serves as the 

 floor of m.in.v of tbe ca\es of the region, .ind is the le\ el ;it which many 

 of th<> lai-u'c spriie^'s emerge. I'.xaniples of this are Hie Leonard and Shir 



