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Gty of Orono Page 2 <br /> SWMP ReNsions Date <br /> is the specific subwatershed that is showing a shortfall and contains the bays of Maxwel% North <br /> Arm, North Lower,Jennings Bay,South Lower,Spring Park,Stubbs, and WestArm. <br /> The subwatersheds for which the Plan indicates excess phosphorus removal are Painters Creek <br /> and Long Lake Creek.All these subwatersheds ultimately tlow into Lake Minnetonka; therefo�e, <br /> the City proposes that this excess from the Painters Creek and Long Lake Creek subwatersheds <br /> count towards meeting the overall required reduction. <br /> This should be viewed as a trading of phosphorus removal reduction requirements between <br /> subwatersheds that all ultimately flow into the same basin, Lake Minnetonka. This will allow the <br /> City of Orono to meet its pollutant reduction requirements in the most cost-e�cient manner as <br /> funding becomes available. Table 9.2 demonstrates the City already faces a budget shorlfall and <br /> will have to rely on other funding sources to meet the phosphorus reduction reguirements; <br /> therefore, being able to rely on this trading strategy is a key e%ment in meefing the reduction <br /> goals. <br /> Comment 2a: The foliowing discussion has been added to Section 9.4: Another method being <br /> used to reduce the phosphorus loading is implementation of ravine stabilization projects. These <br /> ravines have likely been showing minor signs of erosion for hundreds of years;however, <br /> deve%pment of fhe areas without appropriate stormwater controls has led to an increase in <br /> erosion and ultimately the need for ravine restoration/stabilization projects. We are basing our <br /> phosphorous reduction estimate on when erosion began to increase or worsen and is the <br /> justification for the timeframes se%cted. The values provided should also be viewed as a <br /> planning level estimate and a detailed analysis will be provided once fhe projects are completed. <br /> The resuli�will be provided in the annual report to the MCWD. <br /> In addition to this discussion revisions were made to the discussions regarding QP-C1, QP-1, <br /> and CIP-7.The underlined and struck out text represents those revisions. <br /> QP-Ci: The "Offerman Ditch"Ravine Stabilization project(CIP-C1)entailed the repair of <br /> approximately 700'of an eroding swale. The volume voided is based on the cross section <br /> provided in Appendix F. This swale is assumed to have been e�oding since deve%pment occurred <br /> in the 1970's, which altered the drainage patterns and did not provide any on-site storage. The <br /> calculated phosphorus reduction for this activity is presented in Appendix F and totals 26.3/b/yr. <br /> QP-1: The Stubbs Bay ravine stabilization(QP-1)calculation is presented in Appendix F. There <br /> are actually two calcula�ons:one for restoration of a catastrophic failure immediately east of <br /> Tonkawa Road and another for vegetation management(se%ct tree cutting and planting of <br /> grasses and forbs)to the west of Tonkawa Road. The primary failure is 200 feet long, 10 feet in <br /> depth, and IS feet in width. We estimate that the failure has been in the process since this area <br /> deve%ped in the late 1980s and have used 20 years for our phosphorus reduction estimate.�e <br /> `���•� ��`���'���'�`��`The estimated phospho�us load�eduction that can be achieved as a result of <br /> this project is 30.2/b/yr. <br /> CIP-7: The Long Lake ravine stabilization (QP-7)calculation is presented in Appendix F. Here <br /> ravine erosion occurs along the entire 250-foot length with an approximately 8-foot wide by 3- <br /> foot deep failure zone. This area was deve%ped without any stormwater mana4ement controls in <br /> place and it is estimated that the erosion has been occurrin4 for approximately 30 years.-iNe <br />