Sequalitchew Creek
Sequalitchew Nearshore Springs
This freshwater spring emanates from under ground from the DuPont Delta aquifer and flows directly into the Puget Sound.
More about the springs from the 2005 SURFACE WATER AND GEOMORPHOLOGY TECHNICAL REPORT, prepared for Pioneer Aggregate and their mine expansion efforts:
Near-Shore Springs
Several near-shore springs are located along the Nisqually Reach of Puget Sound, adjacent to the
western boundary of the existing mine site. Spring discharges originate from the DuPont Delta
aquifer (CH2M Hill 2001). The largest spring (Large Beach Spring) is located in the intertidal
zone approximately 1,600 feet north of the mouth of Sequalitchew Creek (Figure 1). This large
spring enters Puget Sound at approximately 4 feet above mean lower low water (MLLW).
Discharge data in the original mine EIS characterized the discharge from this spring as ranging
from 11 to 18 cfs, depending on tide height (City of DuPont 1993). More recent data (CH2M
Hill 2001) measured discharges of 9.1 and 14.9 cfs during September 1999 and August 2000,
respectively. Several smaller near-shore springs, located about 600 feet north of the large spring,
had discharge that ranged between 0.05 and 0.24 cfs (CH2M Hill 2001).
Based on the water quality data results presented in the previous mine EIS, waters of the large
near-shore spring generally exhibit good quality (City of DuPont 1993). Significantly high
concentrations of sodium and chloride in addition to high specific conductivity measurements
reported in the original mine EIS were attributed to saltwater intrusion into the spring (City of
DuPont 1993). Salinity data were collected once in 1999 as part of the North Sequalitchew
Creek project in the large beach spring and two smaller springs (CH2M Hill 2001). Salinity in
the large beach spring was 5.3 parts per thousand (ppt), and was 7.7 ppt and 15.3 ppt in each of
the smaller springs.
Sequalitchew Nearshore Springs
This freshwater spring emanates from under ground from the DuPont Delta aquifer and flows directly into the Puget Sound.
More about the springs from the 2005 SURFACE WATER AND GEOMORPHOLOGY TECHNICAL REPORT, prepared for Pioneer Aggregate and their mine expansion efforts:
Near-Shore Springs
Several near-shore springs are located along the Nisqually Reach of Puget Sound, adjacent to the
western boundary of the existing mine site. Spring discharges originate from the DuPont Delta
aquifer (CH2M Hill 2001). The largest spring (Large Beach Spring) is located in the intertidal
zone approximately 1,600 feet north of the mouth of Sequalitchew Creek (Figure 1). This large
spring enters Puget Sound at approximately 4 feet above mean lower low water (MLLW).
Discharge data in the original mine EIS characterized the discharge from this spring as ranging
from 11 to 18 cfs, depending on tide height (City of DuPont 1993). More recent data (CH2M
Hill 2001) measured discharges of 9.1 and 14.9 cfs during September 1999 and August 2000,
respectively. Several smaller near-shore springs, located about 600 feet north of the large spring,
had discharge that ranged between 0.05 and 0.24 cfs (CH2M Hill 2001).
Based on the water quality data results presented in the previous mine EIS, waters of the large
near-shore spring generally exhibit good quality (City of DuPont 1993). Significantly high
concentrations of sodium and chloride in addition to high specific conductivity measurements
reported in the original mine EIS were attributed to saltwater intrusion into the spring (City of
DuPont 1993). Salinity data were collected once in 1999 as part of the North Sequalitchew
Creek project in the large beach spring and two smaller springs (CH2M Hill 2001). Salinity in
the large beach spring was 5.3 parts per thousand (ppt), and was 7.7 ppt and 15.3 ppt in each of
the smaller springs.