Document: 449 U.S. 48 101 S.Ct. 557 66 L.Ed.2d 253 State of WISCONSIN et al., Complainants,v.State ILLINOIS and the Metropolitan Sanitary District Greater Chicago Defendant, United States, Intervenor. MICHIGAN, Complainant, v. NEW YORK, Intervenor No. 1 Orig Supreme Court States December 1, 1980 ORDER Ordered: A. Paragraph 3 Decree entered by herein on June 12, 1967, 388 426, 87 1774, 18 1290, is amended to read as follows: 3. For purpose determining whether total amount water diverted from Lake Michigan Illinois its municipalities, political sub-divisions, agencies instrumentalities not in excess maximum permitted this decree, amounts domestic pumpage lake sewage effluent derived which reaches waterway, either above or below Lockport, shall be added direct diversion into canal storm runoff reaching watershed computed provided 2 decree. The annual accounting period consist twelve months terminating last day September. A forty (40) years, consisting current previous thirty-nine (39) such periods (all after effective date decree), permitted, when necessary, for achieving an average amount; provided, however, that any exceed 3680 cubic feet per second, except two (2) within a year period, may 3840 second result extreme hydrologic conditions; and, first years cumulative algebraic sum each period's minus 3200 2000 second-years. All measurements computations required decree made appropriate officers, Illinois, Corps Engineers Army subject agreement with cost-sharing all reasonable costs including equipment, using best engineering practice scientific knowledge. If conducted under continuous supervision direction cooperation consultation Geological Survey, but limited periodic field investigation measuring device calibration data gathering. audit Engineers. An report issued Best knowledge determined six (6) implementation based upon recommendation majority members three-member committee. committee appointed Chief selected basis recognized experience technical expertise flow measurement hydrology. None employees paid consultants parties these proceedings other than States. convene at least five (5) review method operation procedure. Reasonable notice meetings must given parties. Each party have right attend meetings, inspect facilities structures, access reports take own measurements. B. 5 said adding thereto additional sentence amendment effect October following passage law General Assembly Level Act providing used dilution Ship Canal quality purposes increased three hundred twenty (320) allocations new users water, priority extent practicable goal reducing withdrawals Cambrian-Ordovician aquifer. C. certified copy legislation served filed Clerk Illinois. no raises objection adequacy 30 days service, will complied requirements Order paragraph 1967. Any raised manner set forth 7 Decree. It Further Ordered that: proceeding bear costs. expenses Special Master borne Chicago, three-fifths thereof two-fifths Chicago. Justice MARSHALL took part consideration decision order. STATEMENT OF INTENT AND TECHNICAL BASIS FOR PROPOSED AMENDMENTS TO 1967 DECREE This statement sets intent revisions certain provisions paragraphs proposed change has been designed alter existing prevent effectively utilizing managing (cfs) was allocated. 4 Under system, increasing impervious areas demand elevate risk language violated one if are consistent good management practice. accomplishes following: 6 1. Increases compliance cfs limit running average; 2. During allows cfs-years aggregate (one cfs-year volume resulting year); Limits 115% cfs, permits reach 120% allow conditions. 8 lengthening averaging reduces variability averaged figure, thus decreasing needs held reserve allocated reduce 9 also increase planning time more compatible life types supply facilities, permitting efficient use available without allowable diversion, better resources region. 10 In establishing limits uncertainties behavior interactions between various elements regime future conditions were limiting factors. 11 To estimate variations considered allocation process, forty-four precipitation contained "Water Yield, Urbanization, North Branch River," Northeastern Planning Commission Hydrocomp, Inc., dated 14, 1976, used. These assumed 30% imperviousness factor approximate entire present time. 12 indicate departure mean stormwater 59%. Assuming, therefore, 683 405 cfs. could 13% maximum. Given relatively short record likelihood urbanization, it agreed 15% exceedance, would allowed accommodate high stormflows 40 20%, extraordinary 13 Because year-to-year there series need management, some less average. Calculations departures show exceedance slightly 1500 indicated possibility exists initial greater cfs-years. Since urbanization likely runoff, established 14 maintain long-term

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