3.0 Affected Environment - Knik Arm Bridge and Toll Authority

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Knik Arm Crossing DraftFinal EIS Affected Environment belt system, North Pacific Industries was awarded a contract giving it sole rights to loading gravel, wood chips, peat, coal, and grain onto vessels. Economic development opportunities will increase because of Port MacKenzie’s extensive developable land area and upcoming ferry service, the paving of the Point MacKenzie Road, and the planned improvements to Burma Road between Port MacKenzie and the Big Lake area. 3.4.1.2.3 Alaska Railroad Corporation ARRC is an independent corporation owned by the State of Alaska. ARRC operates 466 miles of main line and 59 miles of branch line. It owns or leases 1,625 freight cars and 42 passenger cars. A major transporter for the state, the Alaska Railroad handles both freight and passengers throughout the railbelt. In the summer months, the Alaska Railroad assists the visitor industry by transporting passengers to popular destinations such as Fairbanks and Seward. ARRC owns 36,000 acres, about half of which is used as right-of-way and for operations. The other half is available for leases or permits to generate revenue. ARRC has facilities in the Mat-Su and in Anchorage. The Alaska Railroad transports freight and passengers north and south through the Mat-Su and Anchorage. It also transports sand and gravel from the Mat-Su to Anchorage for private clients, such as Anchorage Sand & Gravel. The major ARRC facility in Anchorage, including the new passenger terminal, is in Ship Creek. ARRC owns extensive acreage in the Ship Creek area and commercially designated land in Government Hill. During 2004, approximately 67 percent of ARRC’s revenues came from freight and 13 percent from passenger services. The majority of the remaining income is related to real estate activities and federal grant revenue. In 2004, ARRC experienced net earnings of $15.4 million on total revenues of $129.5 million. Railroad assets exceeded a half-billion dollars (ARRC 2005a). ARRC employed 716 persons in 2004. 3.5 Physical Environment The following discussion provides information that should be useful in understanding both the physical and natural setting of the proposed KAC project as well as the potential impacts to the environment from construction and operation of the proposed project. Knik Arm is generally considered to begin at Point Woronzof (west of Ted Stevens Anchorage International Airport), from which it extends 3 miles to the east and then more than 25 miles in a north-northeasterly direction to the mouths of the Matanuska and Knik Rivers. At Point Woronzof, Knik Arm is about 2 miles wide, but significantly deeper (>100 feet) than the adjacent seabed of Upper Cook Inlet (
Knik Arm Crossing DraftFinal EIS Affected Environment While the Knik Arm channel is narrowest at Cairn Point, the channel is also deepest at this point, with depths reaching 180 feet. This bathymetric depression, hereinafter referred to as the Cairn Point Trench, essentially defines the axis of Knik Arm through its extensions to the northeast and southwest. The Cairn Point Trench is remarkable in that its planform and bathymetric relief have remained essentially constant for more than 60 years; this is particularly remarkable when compared with other seabed features of Knik Arm (KABATA 2006c). From this, it is surmised that the Trench is not likely the result of or even significantly affected by modern hydrologic processes. Rather, the Trench is more likely a relict of prehistorical scour events such as the breaching of an ice dam during the period of the Naptowne glacial retreat. The typical cross section for Knik Arm consists of an entrenched inner passageway, with shelves of shallow water on both sides. In the northernmost part of the Arm, the shelves become shoals, which become tidal flats closer to the mouths of the Knik and Matanuska Rivers. The shelves are usually less than 20 feet below the mean lower low tide water line (MLLW). North of the Cairn Point Trench, the maximum depth of the thalweg in the inner trench is about -80 feet with respect to MLLW. The location of the proposed KAC bridge would be within a mile of the northern limit of the Cairn Point Trench. Shallow water in this area forms wing-shaped shelves on both sides of Knik Arm, which at its deepest, reaches to roughly 20 feet below MLLW. The trench in the center of Knik Arm in this area is typically around 65 feet below MLLW at its deepest. Tidal flats in the upper part of Knik Arm are defined as the surface within the banks at an elevation between MLLW and mean high water (MHW). 27 Nonvegetated, these tidal flats appear mostly in the upper end of Knik Arm, starting at Eagle River and becoming more predominant further north, as one approaches the mouths of the Knik and Matanuska Rivers. Below MLLW, such features are characterized as shoals, while above MHW, they are called “lowlands,” or raised tidal flats, as can be seen between the Knik and Matanuska River bridges and Palmer on the Glenn Highway. The dominant climate for Knik Arm, as for all of Southcentral Alaska, is classified as “maritime.” Summers and winters are milder than what is normally seen in continental climates of similar latitude, with average temperatures ranging from 64.8°F in July to 19.2°F in January (Table 3-12). In addition to mild temperatures, the maritime climate of Alaska is characterized by heightened precipitation and persistent winds. 27 Mean high water: a tidal datum. The average of all high water heights (i.e., the maximum height reached by a rising tide) observed over the National Tidal Datum Epoch (Tide and Current Glossary, NOAA, January 2000). 12/18/07 Page 3-93
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3.0 Affected Environment - Knik Arm Bridge and Toll Authority

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