22-27 September 2019
Trade Fairs and Congress Center (FYCMA)
Europe/Madrid timezone

Determining the Source of Deicing Salt Contamination to Bedrock Wells Using Downhole Logging Methods

27 Sep 2019, 09:55
15m
Conference room 2.1 ()

Conference room 2.1

Oral Topic 8 - Groundwater quality and pollution processes Parallel

Speaker

Dr Gary Robbins (Department of Natural Resources and the Environment)

Description

In the Northeast U.S. new types of highway winter deicing procedures along with increasing amounts of salt usage is resulting in an ever increasing number of salt contaminated bedrock wells. The town of Sherman, Connecticut is a case in point. The town has many such open borehole wells drilled into metamorphic bedrock. Despite years of periodic water quality monitoring, and thorough temporal and spatial analyses, the source(s) of the salt contamination has remained elusive. To further characterize the nature of the problem and to define possible solutions, we conducted both conventional and non-conventional borehole logging on 5 contaminated wells. Conventional logging included: fluid temperature, specific conductivity, gamma, caliper, acoustical borehole imaging, and heat pulse flow meter (HPFM) logging under ambient conditions. HPFM was also conducted under pumping conditions. Non-conventional logging consisted of water quality profiling with a sonde which measured temperature, electrical conductivity, pH, ORP, and Dissolved Oxygen. We also applied the Dissolved Oxygen Alternation Method to assess borehole flow conditions. Finally, active flow zones were sampled using Hydrasleve samplers. In general it was determined that the shallow depth to rock, steeply dipping shallow fractures and poorly sealed casing into rock were the main reasons the wells were impacted by the use of salt. Piling of salted snow near wells and well proximity to salted runoff surfaces were also contributing factors. An interim remediation measure was developed which entails flushing wells following the snow season and the use of simple test kits for everyday monitoring. Long term remediation measures were developed to manage runoff surfaces near impacted wells and minimize unnecessary salting near vulnerable areas. Furthermore, it was recommended that all new wells have deeper casing which is cemented into the rock to curtail salt contaminated water transport to the wells in shallow, near vertical fractures.

Primary authors

Dr Gary Robbins (Department of Natural Resources and the Environment) Mr Mark Higgins (Department of Geosciences) Dr Meredith Metcalf (Environmental Earth Science Department) Dr Edwin Romanowicz (Center for Earth and Environmental Science)

Presentation Materials

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