By: RK Water

In the second installment of “Understanding Dewatering,” we’re diving into the importance of representative groundwater sampling — one of the most undervalued aspects of temporary dewatering.

According to Pinyon Environmental, “The groundwater chemistry data collected for permit applications is often flawed because the collection techniques don’t adequately mimic the turbidity associated with the various construction means and methods. This results in either an under- or over-representation of the geotechnical impacts. And under-represented geotechnical condition could result in [the] under-design of the treatment system and [introduce] potential project delays and unanticipated costs.”

Groundwater sampling is essential because each of the following behaviors has the potential to distort groundwater treatment requirements by inadequately characterizing the groundwater chemistry:

• Reliance upon one test well for groundwater sampling.
• Only one groundwater sample analyzed for chemistry.
• Inadequate purging of the test well.

Be sure to uplevel the sampling process by taking heed of potential sample biases. A sampling event is merely a description of general chemistry at a specific moment in time. When test wells are installed, not only will the groundwater table vary according to each well, but the chemistry of groundwater will also fluctuate, sometimes drastically.  Clay layering, bedrock, and underground rivers are below the surface, which is what causes naturally occurring obstructions; these obstructions can introduce chemistry variances that will be overlooked if only one test well is used.

Sampling activities over an extended period of time will provide a more accurate measurement of fluctuations in the groundwater table and its chemistry.  Furthermore, water that is allowed to stagnate with soil, will naturally contain higher levels of heavy metals and other contaminants. Through proper purge procedure, or even extending beyond the minimum, it is possible to obtain lower levels of heavy metals in the sample.

Once dewatering commences, groundwater will begin flowing downstream according to the natural flow of alluvial groundwater. Research also needs to be conducted regarding existing dewatering permits in the vicinity of the project to validate results from sampling activities. More importantly, permits upstream of the project will identify the chemistry to anticipate through continued dewatering activities. In the end, it’s not always about the chemistry of the groundwater within the confines of your shoring, but what’s in your neighbor’s groundwater that may make or break a project.

By: RK Water

Before and during the excavation phase, project developers, architects, general contractors and other project partners take many considerations into account when planning the groundwork for a project including soil analysis, solar angles and other site-specific conditions. One of the most overlooked and under-valued planning activities involves an analysis of groundwater on the project site and how it may affect the project. This step is essential; those who skip it are at risk for project shut down or slow down due to unidentified water.

Dewatering is the action of removing groundwater or surface water from a construction site. It’s most commonly performed due to water that has accumulated during excavations or in places with a high water table. In these cases, the water must be removed for safety in order to proceed with construction as scheduled.

So, what’s required to dewater your next project? We will dive into four key pillars in future blogs to include:

• Representative groundwater sampling
• Flow rates and dewatering methodologies
• Permitting – Which one is appropriate to your project?
• Treatment methodologies

With proper planning, treatment of groundwater on construction projects can be a manageable process that allows your timeline to remain on track.

Did you know that RK Water provides temporary and permanent dewatering services? Our team treats a wide variety of water contamination issues in dewatering operations from Total Suspended Solids (TSS) removal to complicated remediation activities. RK Water approaches every project with a high level of engagement leading up to project commencement followed by unmatched field service during dewatering and remediation operations. Contact Steven Cummings at Steven.Cummings@rk-water.com to discuss a groundwater plan for your next project.