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/ p HARTMAN RETENTION DAM EFFECT OF ALTERNATIVE ACTIONS Results Q I-70 Results Q I-70 with existing with existing west 18" RCP west 18" RCP PEAK FLOOD obstructed. cleaned out �. FLOOD HEC1 CFS @ VOL PEAK MAX PEAK MAX ACTION CONSEQUENCES EVENT FILE DAM AF) CFS ELEV* CFS ELEV* DAMAGES* s� Route flood through 10-YEAR Hartmnl0 154 40 18 103.96 17 103.74 No damage to I-70. Could be confined am outlet and spillway to culverts with inflow ditch work. a (HECl outflow) 25-YEAR Hartmn25 276 -) 53 82 104.55' 37 104.47 For existing - OT I-70 by less than 1'. Minor problems could occur. n . Cleaning west culvert helps a lot. 50 YEAR Hartmn50 411 65 239 104.62' 219 104.61 OT I-70 by slightly more than 0.1'. a Flow amount could be a problem. Breach Dam Flood routed through 10-YEAR Hartbrl0 364 40 169 104.59' 144 104.57 OT I-70 by slightly less than 0.1'. 10' wide breach(1:1 Minor problems could occur. a SS) at outlet 25-YEAR Hartbr25 475 53 266 104.63' 260 104.62 OT I-70 by slightly more than 0.1'. fly, Flow amount could be a problem. liok 50 YEAR Hartbr50 585 65 438 104.69' 426 104.68 OT I-70 by more than 0.1'. Flow **Its �t amount could be a problem. Low it Piping failure along 10-YEAR Hartfnl0 490 40 293 104.64 273 104.63 OT I-70 by more than 0.1'. Flow to =3; obstructed outlet amount could be a problem. during flood event 25-YEAR Hartfn25 592 53 447 104.69 443 104.68 OT I-70 by as much as 0.2'. Flow amount could be a problem. 50 YEAR Hartfn50 695 65 548 104.72 547 104.71 OT I-70 by more than 0.2'. Flow �l amount could be a j2roblem. Do nothing Piping ' ure along 10 Hartf 553 0 3 104.64 273 4.63 Doi notl n as ver m11 obstructed o let 25-Y Hartfa25 702 5 472 104.7 S 10 9 results lowers spillwa SFduring flood eve 50 YEAR artfa50 65 590 .73 588 104.7 this reason, he N tion is nN '1 good alternate c oa * Depths and Damages based upon crude measurements taken on 1/04/02 and 1/11/02, which shows I-70 to be about 4.5' (elevation 104.5) above the low point in theO frontage road J j (datum elevation 100), which stores about 26 AF. An 18" RCP 2'below the access road low point drains the area with a silt bed 1' (elevation 99) above its invert. Presently it is poll obstructed. One alternative is to clean out this culvert**. A 24" CMP also drains this area when water gets to within 1' (elevation 103.5) of I-70. Most beneficial alternative with S ' most impact is to fix the dam and restore the outlet. It may also be even more beneficial to improve the flood detaining characteristics by raising the spillway or reducing its capacity. Cleaning the west culvert under I-70 has little impact unless the dam is fixed. ��