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Mr. Robert C. Mayeron, P.E. <br />Page 2 <br />AUG 81983 <br />2. Unit costs for rehabilitation of infiltration defects - It <br />was indicated at our May 18, 1983 meeting that an itemized <br />breakdown of the unit costs for the rehabiliation of <br />infiltration defects would be provided. As of yet we have <br />not received this information. The rehabilitation unit <br />costs, for the five above listed communities, vary from <br />$600 /gpm to $400 /gpm to $1,500 per million gallons of <br />removable infiltration. All these figures are indicated as <br />being typical. Variation in the cost /gpm can significantly <br />affect the cost effective analysis and subsequent <br />nonexcessive /excessive I/I determination. Please indicate <br />if it is possible to establish one typical estimate for the <br />unit costs of rehabilitating infiltration defects. If it <br />cannot be done please identify why. If a typical estimate <br />can be established then a revision to the cost <br />effectiveness figures should take place. The revision <br />should indicate the effect on the cost effective <br />alternatives chosen for the districts within any of the <br />five above mentioned communities. <br />3. The Little Canada and Golden Valley I/I Analyses indicate <br />that 40% of the infiltration can be removed for one <br />alternative (alternative "L "). The EPA has done <br />significant investigations into the effectiveness of <br />identifying infiltration sourcs and subsequent infiltration <br />removal. They have determined that if 100% of the sewer <br />system is examined approximately 30% of the infiltration <br />sources can actually be identified. In most cases only a <br />portion of the identified infiltration is then cost <br />effective to remove. In the Little Canada analysis the <br />40% infiltration removal alternative was chosen for one <br />district as being both cost effective on the grant eligible <br />and community basis. In the Golden Valley analysis the 40% <br />infiltration removal alternative was chosen as community <br />cost effective in three (3) districts. Please revise the <br />cost data to reflect a 30% or less infiltration removal <br />rate for those alternate now using the 40% removal. Also, <br />indicate if this has any effect on the selection of <br />alternatives being cost effective in either analysis. <br />4. It should be noted that in relationship to the information <br />requested in items 1, 2 & 3 discussed herein before that <br />EPA has established a value of 3000 /gpdim as the cut off <br />point in determining excessive and nonexcessive <br />infiltration. It should also be noted that even though a <br />community may fall below the 3000 / gpdim figure and be shown <br />