Underwater Archaeological Investigation of the Chattahooche River Under the Interstate 20 Bridge for the I-285/I-20 Interchange Reconstruction and Widening Project, Cobb and Fulton Counties, Georgia

The Georgia Department of Transportation (GDOT) is planning to improve the Interstate 20 (I-20) and Interstate 285 (I-285) West interchange in the City of Atlanta, Cobb, Fulton, and Douglas Counties, Georgia (GDOT PI No. 0013918). This project is federally funded through the Federal Highway Administration (FHWA); therefore, SEARCH assisted the GDOT with its obligations under Section 106 of the National Historic Preservation Act (NHPA) by conducting an underwater archaeological investigation of the submerged portions of the Environmental Survey Boundary (ESB) for the project prior to construction activities. This project is part of GDOT’s Major Mobility Investment Program (MMIP), which aims to significantly reduce congestion areas along key freight and passenger corridors. According to the project plans provided by WSP Global, Inc. (WSP), the GDOT proposes to reconstruct the I-20/I-285 West interchange and widen I-20 West. The I-20/I-285 Interchange Reconstruction and Widening Project would provide operational improvements at the interchange and along both the I-20 and I-285 approaches to the interchange. The proposed improvements include construction of collector-distributor (CD) lanes along I-20, construction of additional lanes along I-20 and I-285, and the reconstruction of the I-20/I-285 interchange ramps to improve traffic operations and safety within the ESB. Along I-20, the proposed project would begin around the I-20/Thornton Road interchange in Douglas County and continue east until the I-20/Hamilton E. Holmes Drive interchange in Fulton County, for a distance of approximately 13 kilometers (km) (8.1 miles [mi]). Along I-285, the project would begin just north of the I-285/Martin Luther King Jr. Drive interchange and end near the I-285/Donald L. Hollowell Parkway interchange just north of I-20 in Fulton County, for a distance of approximately 3.7 km (2.3 mi). At the I-285/Donald L. Hollowell Parkway interchange, the proposed project would tie into an adjacent MMIP project (GDOT PI No. 0013917 – I-285 Westside Express Lanes). The proposed project will modify the existing I-20 bridge (Debra Mills Commemorative Bridge) over the Chattahoochee River. Acquisition of right-of-way (ROW) is anticipated, but precise locations and boundaries are unknown at this time. SEARCH was contracted by WSP to conduct a Phase Ia and Ib maritime archaeology investigation of the submerged portions of the ESB. The submerged portion of the ESB measures approximately 365 meters (m) (1,197.5 feet [ft]) within the Chattahoochee River, extending approximately 170 m (557.7 ft) upstream and 195 m (639.8 ft) downstream of the existing I-20 bridge centerline and spanning across the Chattahoochee River from bank to bank. The terrestrial Phase I archaeological survey from GDOT PI No. 0013918 was conducted by New South Associates, Inc. (New South) (Keith et al. 2020). SEARCH collected magnetic and acoustic data within the submerged portion of the ESB to assess the presence or absence of potential submerged cultural resources. SEARCH reviewed the precontact, historical, and geologic background of the region with specific attention paid to the maritime history of the Chattahoochee River. SEARCH identified previous archaeological investigations and reported sites within the area to guide the development of the project research design and assist with interpreting the remote-sensing data. SEARCH’s archival and database review included review of the Paleoindian Database of the Americas (PIDBA); Georgia’s Natural, Archaeological, and Historic Resources Geographic Information System (GNAHRGIS); Georgia Archaeological Site File (GASF); Georgia State Archives; and other digital resources. SEARCH identified four acoustic contacts and one acoustic debris field of unknown source within the remote-sensing data record. SEARCH conducted targeted diver investigations and scientific wading to identify the source of each unknown marine remote-sensing target, which resulted in the identification of Georgia Archaeological Site 9CO786. This site includes remnant structural remains (concrete pilings and iron I-beams) of the original I-20 Bridge over the Chattahoochee River constructed in 1963 and removed/replaced in 1979. SEARCH recommends that Site 9CO786 lacks significant data potential and is ineligible for listing in the National Register of Historic Places (NRHP) under Criterion D. SEARCH recommends that no additional archaeological work is needed within the current submerged ESB.