Deep Time Origins of Sinkhole Collapse Failures in Sewage Lagoons in Southeast Minnesota

Abstract

1850s and 1930s filled many of the conduit systems with soil. Over eighty years of soil conservation efforts have significantly reduced the flux of mobilized soil into the conduits. Those conduits are currently flushing much of those stored soils out of their spring outlets. Finally, the increased frequency and intensity of major storm events is reactivating conduit segments that have been clogged and inactive for millions of years. The karst solution voids into which the lagoons collapsed have formed over 480 million years. The recognition and mapping of this major karst zone will allow much more accurate karst hazard maps to be constructed and used in sustainable resource management decisions.

Creation of a Map of Paleozoic Bedrock Springsheds in Southeast Minnesota

“…The hydrostratigraphy of southeastern Minnesota is further complicated by the extensive development of subvertical joints and fractures, subhorizontal bedding plane parallel fractures, and subtle structural features (Runkel et al, 2014). In addition, Alexander et al (2013) have emphasized the role that the numerous, long, subaerial unconformities in this section have played in the development of the extensive, pervasive secondary porosity and permeability in these rocks.…”

“…Typically they are primarily seen along incised stream valleys where a portion of the Galena Group remains as a cap rock.The Prairie du Chien Group is a major aquifer across much of southeast Minnesota. The visible surface karst features are sparse and are typically further apart than in the Galena karst; large portions of the Prairie du Chien subcrop have little if any perennial surface water flow and groundwater contamination issues are widely present Alexander et al (2013). describe the karst conditions that led to the catastrophic sinkhole collapse of three Municipal Waste Water Treatment Lagoons on the Prairie du Chien.The Duschee Creek Valley area in…”

Karst Influence in the Creation of a PFC Megaplume

“…Karst features, particularly in the OPDC, further facilitate groundwater and contaminant movement. Alexander et al (2013) report the Oneota Formation, the lower member of the OPDC, underwent karstification during the 4 to 5 million year depositional hiatuses that preceeded deposition of the overlying Shakopee Formation. Karstification of the Shakopee also occurred during a 15 million year hiatus prior to deposition of the overlying OSTP (Mossler, 2008).…”

Conduit Flow in the Cambrian Lone Rock Formation, Southeast Minnesota, U.S.A.

“…A region-wide high permeability zone is located at an unconformity between the Shakopee and Oneota Formations of the OPDC (Runkel et al, 2003;Tipping et al, 2006). Catastrophic failures of sewage treatment ponds have occurred where this high permeability zone is close to the land surface (Alexander et al, 2013). The resistant dolostone layer that dominates the plateau is dissected by numerous narrow valleys, especially in the eastern region of the counties near the Mississippi River.…”