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Park 'N Fly-CS 940421 MEMORANDU~I To: Marsha Tunnell, Chairman Planning and Zoning Commission From: Kenneth M. Griffin, P.E., Assistant City Manager/City Engineer Date: April 21, 1994 ~-~---._. There has been some discussion recently concer~ing the status of Park N' Fly in regards to the drainage problems associated with Park N' Fly and G:xteway Business Park. The following should further explain the drainage issue: Gateway Business Park does have an approved plat, filed of record that has a street stubbed out to the east property line of the Park N' Fly plat. This street is shown on the proposed Park N' Fly plat. In conjunction with the plat, Catellus' engineer, Albert H. Halff and Associates, submitted construction plans in early 1992 showing drainage improvements that included underground storm sewer systems in Southwestern Blvd. all the way up to the west property line of Gateway Business Park. The plans also showed the grading of an area south of Southwestern Blvd. to accept the water from Park N' Fly. This is shown on an attached drainage area map from the construction plans for Gateway Business Park dated January, 1992. Because this was the concept we have been working with, the developer of Park N' Fly attempted to match this drainage concept as close as possible. The drainage concept from Catellus anticipated accepting a total of 12.2 acres from the Park N' Fly site. The Park N' Fly construction plans recently submitted for approval show 11.67 acres flowing into the Catellus site. This appears to be consistent with what Catellus has planned all along for their drainage design. The Catellus drainage design also shows a pipe size sufficient to carry runoff from a developed Park N' Fly site. Because Park N' Fly was designing their drainage to match what had been submitted by Catellus, the City was comfortable that the drainage issues had been resolved. However, in early April the City received a letter from Catellus expressing concerns about the drainage. In essence, the letter states that the development of Park N' Fly will increase the runoff from the site and because Park N' Fly has no detention onsite this will cause Catellus to build larger drainage systems. Catellus states that they expect some reimbursement for the size of the drainage system they will need to build through their site because of what Park N' Fly is discharging. As the City Engineer for the City of Coppell, I have a concern with the position that Catellus has taken because the City does not require onsite detention and the City does allow upstream properties to discharge to downstream properties. The development process is such that the lower property owner accepts the upstream water and then discharges it to the next lower property and so on. Also, Catellus has for several years planned their drainage systems to accept the developed runoff from the Park N' Fly site. At this late date to state that they have no intention of accepting the runoff is contradictory to: 1) the plans that they have submitted repeatedly over the past few years for City approval and 2) the accepted design/development processes in Coppell. The Park N' Fly site is at the crest of the hill, therefore their system ,z-ill be a private system and will not require any drainage easements on the plat. The approval of this final plat upon the resolution of the drainage issues will in no way affect what is on the face of the plat when the plat is filed for record. The resolution of the drainage system will only have an affect on the construction plans being submitted for approval by the developer to the City. Based on my analysis of the situation, it is my opinion that the drainage is a construction issue and that the resolution of the drainage will have no impact on what is shown on the face of the final plat for Park N' Fly. Engineering requests that this plat not be disapproved because of drainage concerns. However, if the plat is approved, Engineering requests that it be approved subject to the resolution of the drainage issues in much the same way as the Planning and Zoning Commission approved the revisions to Gateway Business Park several months ago. I will be at the Planning and Zoning Commis::ion meeting and will be happy to discuss this in greater detail at the meeting.