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Page 4 Jirt Monroe Patterson Pass Business Park The flat, low-lying "flood plain" area to the south of Patterson Run was not as clearly defined. Data points along transects from Patterson Run to the toe of slope of the agricultural area were used to determine the limits of the wetland area. This area is considered a "problem area" b:cause agricultural practices have changed the natural condition of the area, and the wetland chwacteristics are mashed by these altered conditions. The top twelve inches of the soil have been disced, disguising evidence of hydrology. However, in areas where there was strong oxidation (as a result of hydric conditions), there were oxidized root channels, providing the secondary indicator of hydrology. The FAC-neutral test of the vegetation provided additional support for the wetland hydrology. Gleyed inclusions, concretions. and orange mattles provided evidence of hydac soil conditions. The dominant plant species in this area were seaside heliotrope (Heliotropum curassavicum= OBL), Bermuda grass (Cynodon dacrv!ot1= FAC), creeping wild rve (Leymus lriticoldes= FAC), and alkali mallow (Malvclla leprosa= FAC). The upland boundary was defined by a dominance of upland plant species with no wetland soils and/or hydrology indicators (see Sheet 3). When this area was re-examined in March of 1998, the channel had changed its course, and during the high waters of this winter's storms, the drainage flowed through the area previously delineated as wetland. Sediment deposits cover the vegetation previously identified growing in this low--lying area. The limits of the wetland/upland remains the same, despite these altered conditions at the end o:this drainage. This drainage is classified as a wetland. Area C Area Cis a flat basin to the west of Patterson Run at the northern end of that drainage. This area had recently been disced, and there was little evidence of vegetation in that area. 777e soils in this area, however, appeared to have a higher silt component than the surrounding soils, indicating this area likely serves as an overflow basin, or floodplain. for the water at the northern erd of the Patterson Run drainage before it flows into the culvert under the .Delta Mendota Canal. The elevation of the crossing noted on Sheet 3 is below 190. Figure 3 provides a detail of the topography in this area. The elevation of the top of the culvert under the Delta Mendoto Canal appears to be between 193' anf 194. Area C as noted on Street 3 represents an average between these two elevations. Area C is classifted as waters of the U.S. (see Sheet 3). Drainage A This ephemeral drainage flows from a culvert under the California Aqueduct in a deep incised channel, at which point the channel is 15 feet across. As it flows across the site, the channel narrows to 2 feet across. The banks of the channel are dominated by cultivated oats. Much of the channel is unvegetated, with open water across much of the channel bottom. RMI Irl SULACL %I A\ A(.L I'I ISI Li \d TIUSAL, INC- --