3.0 Affected Environment - Knik Arm Bridge and Toll Authority

Knik Arm Crossing DraftFinal EIS
Affected Environment
secondary treated effluent into Eagle River, which enters Knik Arm; the Palmer WWTF
discharges secondary treated effluent into the Matanuska River, which flows into Knik Arm;
and the two military bases discharge into Anchorage’s wastewater treatment system, which is
processed by the Asplund WWTF. Wastewater from the Wasilla WWTF is discharged to a
State of Alaska-permitted, 9-acre drain field, and no pollutants from this source enter Knik
Arm.
Eight polluted water bodies flow into Knik Arm and serve as sources of water pollution into
Knik Arm. Cottonwood Creek and the Matanuska River input near the head of Knik Arm.
Eagle River inputs into Knik Arm north of Anchorage. Five creeks—Ship, Campbell,
Chester, Fish, and Little Campbell—input into Knik Arm from Anchorage. Water quality
information on these five water bodies is given below.
3.8.1.3 Anchorage
3.8.1.3.1 Water bodies (lakes, streams, ponds)
Major water bodies on the east side of Knik Arm (Anchorage area) include Ship Creek, the
Eagle River, Peters Creek, Sixmile Creek, and the Eklutna River (Figure 3.53). The Eagle
River is a glacial waterway that originates at the base of the Eagle Glacier in the Chugach
Mountains. Eagle River discharge is generally high from June through September. A midsummer
peak discharge coincides with the maximum melting of Eagle Glacier followed by a
later peak in response to early fall precipitation (U.S. Army 2004). Lowest discharge is from
December through April (USGS 2005). Important lakes within the Anchorage area include
Sixmile Lake, Eklutna Lake, Mirror Lake, and Beach Lake.
Perennial streams within the Anchorage portion of the Study Area include Ship Creek, the
mouth of Sixmile Creek, and Cherry Hill Ditch. Ship Creek is a nonglacial stream that
originates at Ship Lake in the Chugach Mountains and flows to Knik Arm. Numerous water
diversions from Ship Creek occur as it flows through Fort Richardson, Elmendorf, and
Anchorage. Sixmile Creek occupies a valley created by an old channel of the Eagle River.
Sixmile Creek was once a spring-fed stream, and is now flooded for most of its length by
Upper and Lower Sixmile Lakes (Rothe et al. 1983). Cherry Hill Ditch, a smaller stream
draining the developed areas of Elmendorf, flows to the eastern side of the POA before being
diverted into a storm drainage structure and flowing west into Knik Arm.
Intermittent streams are present along the coastal bluff from the POA north to Cairn Point.
These seasonal streams are typically high-gradient, low-flow streams with gravel or cobble
streambed substrate. A small pond is also located north of Ship Creek and south of Whitney
Road. Figure 3.53 shows the water bodies in the Anchorage and Mat-Su portions of the
Study Area.
3.8.1.3.2 Water quality
According to ADEC’s Integrated Water Quality Assessment Report, five Anchorage-area
creeks—Ship, Campbell, Chester, Fish, and Little Campbell—are identified as Category 5,
CWA Section 303(d) impaired water bodies requiring TMDL (ADEC 2003).
3-174 12/18/07