Journal of Cold Regions Engineering

Freshwater resources in rural Alaska communities, especially those underlain by permafrost, are particularly vulnerable to impacts from nearby waste facilities. The authors investigated the connection between rural solid waste facilities and transmission of pathogenic organisms into nearby water resources by evaluating the (1) prevalence of pathogen indicators E. coli and Enterococcus sp. proximal to cold region waste facilities, and (2) partitioning behavior of both organisms in a controlled snowmelt lysimeter test. Results reveal that E. coli and Enterococcus sp. preferentially attach to and migrate with soil particles in surface waters and are transported off-site during snowmelt runoff. Enterococcus sp. had higher and more sustained viability in cold environmental conditions than E. coli. E. coli and Enterococcus sp. were found in surface waters and soils in the concentration range of 0.7–3.5 mean log most probably number $(\mathrm{MPN})/100\mathrm{mL}{\mathrm{H}}_2\mathrm{O}$. All microbial samples indicated strong site-specific variability.

Agro-based products and complex chlorides/minerals (CCM) based products are increasingly employed in snow and ice control operations, either used alone or more commonly as additives for chloride-based products. Recent studies have shown that agro-based or CCM-based products have the potential to improve the overall deicing and/or anti-icing performance and reduce the corrosion and environmental risks. However, the effectiveness of such products has been limited to qualitative field observations, and their specific role in snow and ice control is poorly understood. This work consists of a systematic laboratory investigation, which focuses on the thermal properties, ice melting behavior, and corrosivity of four agro-based deicers and two CCM based deicers. First, CCM-based deicers do not exhibit significantly better ability to lower the freezing point of water when compared with NaCl, but they feature slightly better ice melting capacity at $-9.4°\mathrm{C}$ (15°F) than NaCl. Second, agro-based additives appear to significantly lower the freezing point of 23 wt% NaCl brine, but do not significantly improve the ice melting capacity at $-9.4°\mathrm{C}$ (15°F) or $-3.9°\mathrm{C}$ (25°F), thus implying their role as cryoprotectants. Third, CCM and agro-based deicers do not exhibit significantly lower characteristic temperature than NaCl. A very strong positive linear relationship exists between the eutectic temperature ($T_e$) and the characteristic temperature ($T_c$) of the tested liquids, indirectly confirming the validity of using differential scanning calorimetry (DSC) thermograms to assess liquid deicers. The gravimetric method reveals that CCM-based deicers exhibit slightly lower corrosivity to carbon steel than NaCl, and agro-based additives exhibit significant benefits in reducing the corrosivity of 23 wt% NaCl brine. The electrochemical method reveals that although the beet-based additives do not significantly alter the corrosion potential of carbon steel, the other type of additives moved the corrosion potential to a much more positive level, implying anodic-type inhibitor at work.

The authors introduce an experimental method that focuses on the flow-thermal relation and the visual observation of heat distribution around a cooling pipe in sand under the flow condition. This experiment aims to understand the effect of seepage flow on the heat transfer behavior of sand under cooling and freezing conditions due to a vertically buried heat exchanger pipe. This method combines a flow test, cooling or freezing processes, and the visual observations of temperature profiles with saturated Toyoura sand as the heat transfer medium. A vertical copper pipe inserted into the sand medium is used as the thermal exchanger, while an infrared thermograph is used to measure and visualize the surface-temperature profile of the specimen. The heat transfer distribution behavior is investigated by conducting a series of cooling and freezing experiments on the specimens with variation of the flow rate condition, initial condition, and pipe depth. The thermograph observation results show how water flow obviously affects the shape and intensity of the heat distribution.

To facilitate excavation and foundation work in seasonally freezing or permafrost regions, the frozen soil must be thawed, either by natural (solar) thawing, or by artificial thawing where an auxiliary heat source is utilized to accelerate the process. In this paper, the process of rapid thawing of frozen ground subject to hydronic heating is studied. In particular, the performance characteristics of the method is evaluated through full-scale thawing experiments performed on three types of homogenous, initially frozen soils. The results from two separate experiments, carried out during the winter of 2011 and 2012, were compared. The corresponding soil temperature increase, phase change, and variation in water content for each type of soil were monitored. The results from both winter seasons show similar trends, with comparable and considerable higher thaw rates for gravelly sand ($\sim 3.5\mathrm{days}/\mathrm{m}$) and silty sand ($\sim 4\mathrm{days}/\mathrm{m}$) compared with crushed gravel ($\sim 11.5\mathrm{days}/\mathrm{m}$). Furthermore, thaw rates compiled from thermistor strings in tubes embedded in the ground are overestimated compared with similar temperature readings based on thermocouples in direct contact with the soil.

An unheated, insulated (R19) shop building with a concrete slab-on-grade floor was constructed at a site without permafrost near the ocean shoreline in Nome, Alaska. During the first 9 years after construction, the floor slab’s north side moved 0.17 m upward relative to its southeast corner. An investigation revealed that permafrost had formed under the building. The shop building’s presence caused an uneven energy draw from soil under it. The permafrost formation and floor slab upward movement patterns together indicate that the energy draw is greatest at the building’s northern exposure, which is where the least solar radiation had been received. This transfer of energy primarily exists because when the shop building was constructed the difference between terrestrial radiation emitted and solar radiation received increased at the site. Results of engineering analyses indicate that the shop building’s energy draw is equivalent to an annual 5 to 10°C temperature decrease, respectively, between its southwest corner and north side.