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area is either west and north to subwatershed OL17 eventually reaching Olson Lake, or east to subwatershed JAN16 in the City of Lake Elmo, a landlocked subwatershed. The City of Oakdale submitted information prior to VBWD approval of the Oakdale Surface Water Management Plan which showed existing flowrates from the OL13/OL14 subwatershed ranging from 9 to 17 cfs. VBWD conducted a survey in September, 1992, to determine the ultimate overflow point from the OL13/OL14 watershed. A 15-inch diameter culvert crosses Ideal Avenue North, just south of39th Street North. The east end of the culvert was plugged at the" time of the survey. Assuming the culvert is unplugged, overflows from subwatersheds OL13 and OL14 would most likely be directed to subwatershed JAN16. Assuming the culvert remains plugged, the overflow would be directed to the west and north, to subwatershed OL17 and Olson Lake. Since neither Olson Lake nor Deer Pond was designed to handle this additional volume of water, the outflow from this watershed needs to be directed elsewhere, most likely to Eagle Point Creek via subwatershed EPN8. Although the City of Oakdale's Surface Water Management Plan calls for over 60 acre-feet of storage to be provided in this area, the proposed peak discharge from OL14 is 66 cfs. To move the water from this area to Eagle Point Creek will require either an extensive ditch system or a pumped outlet because subwatershed JAN16 is landlocked. Therefore, a diversion is needed to carry the water to subwatershed EPN8 and the drainageway east of Ideal Avenue North which carries water to the upstream side of the T.H. 5 culvert. The Oakdale Surface Water Management Plan presents two options for the OL13/OL14 drainage area: Provide all of the necessary storage on -site, within the City of Oakdale. 2. Provide the majority of the necessary storage on the property east of Ideal, in the City of Lake Elmo, and provide the remainder of the needed storage on -site. Since the City of Oakdale would be routing storm water through the City of Lake Elmo, an improvement project may be required prior to development of the site. In either case, discharge to Eagle Point Creek will either be limited by the existing capacity of the in -place downstream system or the downstream system will require upgrading to handle any increased discharge. Based on the already -limited downstream capacity of the creek, the allowable discharge from the OL13 and OL14 area will likely be less than that called for in the Oakdale Surface Water Management Plan. The Oakdale Surface Water Management Plan states the following: The details of the-offsite system are difficult to determine until development proposals for OL-13/OL-14 are brought before the City. At that time, a study to determine detention needs, conveyance system design, and land acquisition will be prepared. Any development occurring prior to the completion of this study will be required to provide detention onsite (within OL-13/OL-14). VBWD will study the impact of the proposed development(s) on the downstream storm water system at that time. Any proposed improvements will require VBWD approval. 4.2.10.3 VBWD Water Quantity Management Goals VBWD proposes to improve the creek channel capacity along the north fork an provide at least one detention basin along the creek to reduce downstream erosion, sedimentation and flooding. The detention basins would provide the added benefits of flow 23\82\045\SEC4.RPT\KMH 36 DRAFT: June 23, 1994