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Rolling Hills Development Environmental Sampling Report Elk River, Minnesota October 10, 2023 AET Report No. P-0025977 AIM IN SCAN €HGINEEHlNG TESTING 1.0 INTRODUCTION The city of Elk River plans to dredge sediment deposits from six stormwater ponds in the Rolling Hills Development, located near 226th Lane NW. Brandon Wisner, Engineering Project Manager, requested engineering assistance to complete this project. On September 8, 2023, the Client authorized American Engineering Testing, Inc. (AET) to provide environmental services for characterizing sediments in the stormwater pond so that the dredged sediments may be managed properly upon removal. Figure 1 shows the location of the stormwater pond sampling locations in the Rolling Hills Development (Site). The Site is a residential area, approximately 30 acres in size. The stormwater ponds are spread out through the development, with each pond less than 1 acre in size. Most of the ponds are overgrown with wetland vegetation and little standing water. 2.0 SCOPE OF SERVICES AET performed a sediment assessment in general accordance with the May 2017 Minnesota Pollution Control Agency (MPCA) document Managing Stormwater Sediment Best Management Practices Guidance, wstrm4-16 (May 2017 Stormwater Sediment Guidance). The scope of services completed by AET consisted of: • Collecting two samples from each pond, for a total of twelve (12) sediment samples. Samples were collected to depths of 2.0 feet below the pond bottom, or native soil. The borings were advanced at the inlet and outlet of each stormwater pond. Each sample location was logged in one -foot intervals noting sediment types and other characteristics (i.e. staining, odors). • Collecting a sediment sample from each of the borings for laboratory analysis of arsenic, copper, polynuclear aromatic hydrocarbons (PAH), and carcinogenic polynuclear aromatic hydrocarbons (cPAHs). • Preparing this report presenting the testing results and recommendations for managing sediment/soil dredged from the stormwater pond and the expansion area. 3.0 SEDIMENT SAMPLING AND TESTING 3.1 Sediment Collection AET collected a total of twelve (12) samples, two from each of six stormwater ponds (Figure 1). The City of Elk River provided a Rolling Hills Development plan sheet which showed the pond locations. Samples were collected from borings advanced 0 to 2 feet into the pond sediment. In general, all the encountered pond sediment was silty or clayey sand with varying amounts of organic material. Appendix A provides a general description of sampling methods used during this project. Page 1 of 4