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Sinkhole treatment to improve water quality and control erosion in southeastern Minnesota
Published in Barry F. Beck, Felicity M. Pearson, Karst Geohazards, 2018
The Lanesboro state fish hatchery is located near the city of Lanesboro, in Fillmore County, Minnesota (Figure 3). The hatchery is a major supplier for the fish-stocking programs of the Minnesota Department of Natural Resources (DNR). The hatchery is supplied by large springs discharging from the Oneota Dolomite of the Prairie du Chien group at the base of a bluff. For many years, the hatchery springs experienced water quality problems, including high levels of sediment, nitrate, and bacteria, especially after storm events. The sediment and nitrate are of particular concern to the hatchery managers because of their effects on the fish stock.
Coastal Erosion and Shoreline Change
Published in Yeqiao Wang, Coastal and Marine Environments, 2020
Along rocky coasts, storm waves may pound the base of steep coastal bluffs, slowly weakening the bluffs and eventually causing a collapse of the bluff. Bluff erosion is more extreme in California during years with a strong El Nino, which brings more frequent storms and higher water levels to the Pacific U.S. coast. Sea level rise can also accelerate bluff erosion. All bluff erosion is permanent although the collapsed debris may temporarily protect the base of the bluff from further erosion. Future storms or sea level rise will eventually remove the debris and renew bluff erosion.
Energy Efficient Operating Strategies
Published in Frank R. Spellman, Fundamentals of Public Utilities Management, 2020
Energy Improvement Management Plan—while TMWA relies on gravity as much as possible, in a mountainous community, pumping water is a reality. The Chalk Bluff Plant is TMWA’s largest water producer and the highest energy use facility. The high energy use is due to the pumping of water uphill from the river into the plant. To reduce energy consumption at Chalk Bluff, the implementation plant consists of two parts: (1) optimizing the time-of-use operating procedures and (2) water supply capital improvements. The first strategy is to optimize time-of-use operating procedures by creating a mass flow/electric cost model of the treatment and effluent pumping processes. The model will be used to predict how changes to the operating procedure will affect electricity cost. In 2010, TMWA spent $938,000 on 7.8 GWh for non-water supply processes of the plant. This project intended to reduce non-supply electric costs by 15 percent or $141,000.The second project involves water supply improvements to the Highland Canal which transports 90 percent of Chalk Bluff’s water directly to the plant using gravity. The improvement plan will allow 100 percent of the water to be brought to the plant using the Highland Canal and meets multiple objectives. Improvements will be made during winter months when customer water demand is the lowest to reduce the water supply pumping costs during construction. Currently, TMWA spends $60,000 on 0.5 GWh for water supply pumping at the Chalk Bluff Plant. Energy use will be zero when the project is complete. The design life of the new infrastructures is over 100 years and it will require no energy to operate.
Numerical analysis on mining-induced fracture development around river valleys
Published in International Journal of Mining, Reclamation and Environment, 2018
C. Zhang, R. Mitra, J. Oh, I. Canbulat, B. Hebblewhite
The impacts of mine subsidence on these significant natural features have been extensively investigated [1–4]. The environmental consequences of these impacts mainly include loss of surface flows to the subsurface, loss of standing pool, adverse water quality impacts, development of iron bacterial mats, cliff falls and rock falls, impacts on aquatic ecology etc. [4], as illustrated in Figure 2(a) and (b). Field investigations have shown that mining-induced valley closure subsidence can lead to the formation of voids beneath watercourses, often in the form of open bedding planes which can act as underground flow paths for groundwater and stream water [5]. Therefore, there is significant potential for surface water to flow through the subsurface fracture network in the area that has been affected by valley closure subsidence. Figure 2(c) depicts the process of water flow through a mining induced fracture network in an area that was affected by valley closure.
Assessing bank erosion hazards along large rivers in the Anthropocene: a geospatial framework from the St. Lawrence fluvial system
Published in Geomatics, Natural Hazards and Risk, 2021
Jean-François Bernier, Léo Chassiot, Patrick Lajeunesse
The FES is characterized by the presence of high (>5 m) soft and rocky bluffs with 46% showing an EI > 0 (Figures 6(B) and 7(B)). These cliffs are generally steep and mainly composed of shales and unconsolidated materials sensitive to meteorological alteration by frost and water, which make them more vulnerable to terrestrial erosion processes than other riverbank types in this area (Figure 12(A)). Roland et al. (2021) have highlighted that strong seasonality that promotes freeze/thaw cycles events is a dominant process on bluff recession in cold riparian environments. Within the FES, 83% of the unconsolidated cliff segments are partially or completely vegetated, but field surveys suggest that they can quickly become unstable (Figure 12(A)). Erosion along soft bluffs generally results from the joint action of slow and continuous mechanisms (i.e. freeze/thaw, seepage and desiccation) with rapid and occasional mechanisms such as runoff and mass-wasting processes (Joyal et al. 2016; Chassiot et al. 2020; Volpano et al. 2020; Roland et al. 2021); one striking example is the 2019 landslide that destroyed a marina in Deschaillons-sur-Saint-Laurent, nearby Portneuf (Figure 1(B)). In addition, several slide scars, some of which are now vegetated, remain visible on LiDAR data along bluff segments. This information suggests mass-wasting is an important process of riverbank erosion within the FES. Moreover, 9% of the riverbank segments correspond to rocky cliffs along the FES (Figure 7(B)). These cliffs consist, for the most part, of friable sedimentary rocks where freeze-thaw cycles are very active, especially on about 20% of these riverbanks where an absence of vegetation is observed. Although their annual retreat rates are usually slow, rapid mass-wasting processes such as rockfalls and skinflows already occurred in the area. However, few studies have described the lithostratigraphy of these bluffs (Besré and Occhietti 2007; Occhietti 2007) but without addressing them in terms of geohazards.