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Draft – 10/1/15 Performance Specifications City of Lino Lake Proposed Stormwater Outlet to Peltier Lake DOCUMENT PURPOSE: The purpose of this document is to describe the functional design of the project upon which the performance characteristics (specifications) and the determination of “no adverse impact” depend. The performance specifications include the physical characteristics, operation and performance of the mitigation measures committed to by the City. The District acknowledges the functional design for the project may change. These changes under no circumstances can result in an increase in the 2-year 24 hour, 10-year 24-hour and 100-year critical duration peak discharge and runoff volume or the timing of the peak discharge to Peltier Lake from that represented by the City in Comprehensive Stormwater Management Plan for the Proposed Peltier Lake Outlet Lino Lakes, Minnesota (January 22, 2015) and Comprehensive Stormwater Management Plan for the Northeast Area of Lino Lakes, Minnesota (September 11, 2015) as reviewed by the District Engineer and summarized in Technical Memorandum, Lino Lakes Comprehensive Stormwater Management Plan (CSMP) District Engineer Review (July 9, 2015). PROJECT DESCRIPTION: The City of Lino Lakes (the City) is proposing to construct a new stormwater outlet to Peltier Lake (the Project), which would serve a 1,430 acre area within the northeast portion of the City. The area is currently served by Anoka County Ditch (ACD) 72, ACD 55 and natural drainage features. Runoff generated by precipitation events now reaches Peltier Lake through ACD 72 which drains portions of northeast Lino Lakes on either side of I-35E and flows directly to Peltier Lake; through ACD 55 which discharges to Clearwater Creek and flows to Peltier Lake; and for some lands east of Peltier Lake by overland and natural drainage features directly to Peltier Lake. Plate 1 provided by the City shows the current drainage patterns and the division of the drainage area into regions. These regions are the organizational areas for the mitigation proposed by the City, to ensure no adverse impact under the District’s Rule I, Drainage Systems. A portion of the drainage area is located in the city of Hugo. The current capacities of ACD 55 and ACD 72, both of which are clay tile systems constructed in the early 1900s for agricultural purposes, are insufficient to convey runoff consistent with the City’s planned level of development. STANDARD FOR DETERMINATION OF NO ADVERSE IMPACT: The definition of adverse impact utilizes criteria that the District applies programmatically under Rule I. 1. No damage to structures, buildings and infrastructure as a result of an increase in flooding (increased elevation, velocity or number of days of inundation); 2. No property damage or increased maintenance costs resulting from an increase in the amount of erosion, bank failure or accelerated sedimentation; 3. No decrease in water quality resulting from an increase in phosphorus and sediment loads; and 4. No permanent loss of the use of flood storage volume during the flood peak within the Anoka Chain of Lakes.