2525 W CASINO RD BASE FILE 2018-01-01 MF Import

� � � o �x .. , C. M Hx � �e c� oH 7pa 'il H'il x �� MEMORAiJDUM l*f O H ONr ��r� TO: Gordon Witcher t" y� FROM: Jane Zimmerman �yHH O y H DATE: April 10, 1990 Cg] fA a y� SUBJECT: Paine Field Business Park Wetlande Mitiqation Fy HOfn The wetlands mitigation plan for the above project locates the required grass-lined swales in the buffer area of the mitiqation wetlands. Th�s location of the grass-lined swales will not allow proper functioning of either the swales or the buffer area. To be effective, the vegetation in grass swales requires annual cuttinq to remove pollutants present in the plant tissues from bioloqical up-take. Periodically it may also be necessary to completely rejuvenate the swales to ensure continuing pollutant removal. Fejuvenation requires the removal of existinq vegetation and soils. Neither main- tenance activity is appropriate for the buffer area of a '�' wetland. ��' To be effective, the buffer area must be planted with dense trees and shrubs. These plantings compromise the function '�' of the grass-lined swales in two major ways. First, the density and nature of the shrubs make access to th? swales ��' difficult. The probability of adequate maintenance is therefore decreased. ' ' Se� ondly, the density of the buffer area plantings, intended �� to provide a shaded water corrider to reduce water temperatures, results in inadequate light for the grass in '_' the swales. Dead qrass; and a ncn-functional swale, is the ' result. For the above reasons, grass-lined swales should not be � 1 placed in the buffer area of a wetland. The Paine Field '�' Business Park is no exception. The biiffar area for the ketlands is already a minimal 25 feet. Placement of the grass-lined swales in the buffer area will result in �' inadequate function of Uoth the swales and the buffer area. ��