7007 SEAWAY BLVD 2016-01-01 MF Import

8. VARIANCES FROM INITIAL PLAN Variances in the construction of the Narbeck project from what was shown on the plan occurred for several reasons. The most common reason for changes was to preserve significant habitat features such as snags, large trees, or significant patches of vegetation. Some changes were made by the airport as a result of negotiations ' with the original property owners, and other administrative changes. Other reasons for changes include small errors in the original plans, information gaps in the initial topographical survey, availability problems with some of the specified plants, construction supplies, etc. The following is a list of all changes irom the original plans, the reasoning for these changes and the outcome of the changes as they relate to the entire project in general. In all cases, the first priority in considering changes to the plan was the improvement of environmental protection. 1 ) Change in leaky berm elevation. The elevation of the lowest permeabte layer of the leaky berm is shown on the plans to be installed at 530.74. Jane Zimmerman, of the City of Everett Public Works, felt that the beaver dam should continue to control the historic outlet of Narbeck Swamp. An agreement was made that the leaky berm be installed six (6) inches beiow the present elevation of the beaver � dam at the outlet �f Narbeck Swamp. The top of the dam was surveyed on the 9th of September, 1998 at 528.24. Consequently, the elevation of the lowest permeable layer of the leaky berm was installed at 527.74, or three inches below the elevation shown on the plans. This change n elevation will �ot significan!ly alter the hydrology of the project. Areas upstream of the leaky berm will not pool up quite as hic±��. On the downstream side of the Ieaky berm, water will begin to flow at a lower elevation, but the total amount of water charged through the system will be the same. 2) Grading modified in the vicinity of the large Douglas-fir tree in the central portion of the site, along the eastern edge of grading. Grading was steepened to accommodatP saving the tree. 3) A pond cell was moved roughly 20 feet south of its proposed position. This cell is located along the east edge of the overtlow channel, north of the old access road culvert. Moving this cell allowed two significant habitat snags to be preserved. 4) A pond cell was shifted west and truncated to acce,�modate a habitat snag and to preserve desirable vegetation. This modification is located along the east edge of the overtlow channel, south of the old access road culvert. 44