One of the biggest overlooked risks at a construction site is that of groundwater. Though it is not obvious that a steep hill or an active fault can inundate an excavation. It may bring destruction to adjacent buildings or delay a project by weeks. Hence, create tens of thousands of dollars in unwelcome expenses.

Groundwater elevation can vary rapidly in LA neighborhoods. So, the design of a dewatering system most critical yet often neglected consideration for initial project planning.

In this article, you will learn the meaning of dewatering, when it’s necessary, how it is planned, and its potential consequences if it is not done for any reason.

Dewatering means temporarily removing groundwater from an excavation or construction. It usually allows work to proceed on dry, stable ground in that area. Without it, seeping can cause unstable soil, slow down or halt construction, and create unsafe working conditions for crews.

Los Angeles presents a wide range of groundwater conditions. The areas of Marina del Rey, Playa del Rey, and portions of Downtown LA near the LA River generally have shallow groundwater tables.

Other areas, especially in hills and higher neighborhoods, may have groundwater far below the surface. In some places, there may be no groundwater within excavation depth. Soil conditions vary widely across the region.

The dewatering system design always starts with site-specific data, not assumptions carried over from a nearby project. Within Los Angeles, the LADBS Grading Division requires a soils report for most foundation excavation and grading permits.

An apparently simple project can turn out to be a full-fledged dewatering project. A dewatering system may be necessary when:

1. Runoff enters the area during excavation to a depth below the seasonal high groundwater level.
2. Part of the project provides for a parking structure, basement, or below-grade unit.
3. Utility trenches or pipeline installations cut across areas of saturated soils.
4. Close to sea, river, or historic floodplain
5. Dry working surface is necessary with the installation of deep foundations (piles, piers)
6. Planned tunnel, shaft, or large-scale grading work.

Only a clear depiction of underground conditions can lead to perfect dewatering system design. So, Engineers and designers assess the area before designing the dewatering system.

Groundwater investigation determines the depth, fluctuation, and direction of flow of groundwater and the water table to adjacent soils. The data consist of monitoring wells and regional groundwater data from previous monitoring activities.

It also includes data in the State Water Board’s GeoTracker database for existing wells) and site-specific borings. Groundwater levels can fluctuate significantly in LA from wet season to dry season. So, sometimes worst-case (wet seasons) influences the investigations, as seen on the drilling day.

The right environmental inspections prevents project delays and avoid risky project budget issues. Properly framed inspections safeguard schedules, jobs and your project budgets.

The Centers for Disease Control and Prevention (CDC), however, offers guidance on private well testing and preventing waterborne diseases. EPA also provides current PFAS and drinking water information. The Safe Drinking Water Act establishes enforceable standards for public water systems set by the U.S. Environmental Protection Agency (EPA).

Water testing is important for public health too. Getting filthy drinking water with germs is a significant health threat. For example, E. coli or heavy metals, lead, PFAS,

Construction is a regulated source of water pollution in itself. Grading and digging can cause muddy runoff, which is detrimental to the storm and stream systems. Thus, construction sites greater than 1 acre will require stormwater permits under the EPA’s National Pollutant Discharge Elimination System. These rules are under the jurisdiction of the State Water Resources Control Board and its regional boards in California.

Old contamination comes on top. Past plumes can pollute groundwater and persist for decades. It generally comes as a consequence of former industrial sites, leaking underground storage tanks, or past dumping.

This is why, as part of a Phase II environmental site assessment, we take soil and groundwater samples. Typically, we need a Phase II assessment.

Appropriate wall type according to your property depends upon the slope shape, the soil, groundwater, and site access. A geotechnical investigation determines the above-mentioned parameters. On fire-scarred lots, do not assume a soils report written before the fire is still valid.

Burned slopes behave differently compared to the real conditions. So, most cities and counties will require an updated soils study before a new retaining wall approval.

For testing the water quality, you should follow the methods below:

Field tests are straightforward, consisting of measurements of the pH, temperature, dissolved oxygen and turbidity using field pH, temperature, and turbidity meters and probes. Testing can be quick and can be helpful for initial assessment. But there is only an approximation of results and no real proof.

The monitoring wells enable multiple sampling from one point over time. Monitoring of contamination plumes, verifying cleanup effectiveness, and observing groundwater in deep excavations is possible with groundwater monitoring wells. The U.S. Geological Survey (USGS) has abundant groundwater data that are often used to supplement site-specific monitoring programs.

For legal and/or engineering significance, results from certified laboratory analysis are preferred. We take samples in a controlled environment with compliance rules and document the chain of custody. We then perform analysis that uses EPA-approved methods at an accredited analytical laboratory. It is the standard to comply with for drinking water, discharge permits, and environmental site assessments.

Instrumentation includes in-line sensors and data loggers. These instruments provide real-time monitoring for treatment plants and critical infrastructure. They are able to detect water quality issues when they occur.

You should identify every authority over your project early. You will know the exact requirements from each of them, and it will not delay the project. Water testing requirements come from several overlapping authorities:

• Federal public water supplies are under the Safe Drinking Water Act. Surface Water discharge is regulated by the Clean Water Act and the NPDES program. The EPA operates both departments.
• State of California (California State Water Resources Control Board) has set the discharge permits and water quality goals. Nationwide, utilities follow industry standards as developed by organizations such as the American Water Works Association (AWWA).
• Transportation and public works: The agencies establish their own regulations concerning work in their area. Caltrans has comprehensive requirements regarding stormwater and water quality for development located in the State highway right of way. Every project should follow Los Angeles grading and drainage codes from LADBS and the city’s Stormwater Ordinance.

Consider professional testing in these situations:

• Before buying or developing property — as part of Phase I/II environmental due diligence
• Before foundation design in areas with shallow groundwater — to check for corrosion and sulfate exposure
• Before and during construction de-watering — to get and keep discharge permits
• After suspected contamination — nearby industrial activity, old tanks, or unusual odors and staining
• For ongoing permit compliance — scheduled sampling under NPDES or local discharge permits
• For private wells and small systems — routine yearly testing for bacteria and nitrates, following EPA guidance for private wells

A qualified environmental or geotechnical firm follows a defined process:

1. Examine and devise a sampling plan
2. Correctly collect samples and maintain them appropriately
3. Maintain chain of custody, submit samples to an approved laboratory
4. Interpret the results

Without a professional engineer, raw lab data and design advice or compliance results don’t have value. Home test kits are suitable for basic well screening; however, you can’t obtain a permit based on the results.

Water quality testing is beneficial for waterproofing systems and the communities above. Certified testing provides engineering decisions from an unknown situation. Such as for selecting sites for a foundation, dewatering program, or simply conducting a due diligence survey

Do you need water quality testing, groundwater monitoring, or environmental compliance support at your project? Call in our group of accredited Engineers or Environmental experts today for a cost-free expert consultation and estimate. We will develop a sampling program that meets all the agencies’ requirements and have a voice in your project.

How much time does it take to test?

Field tests provide results immediately. However, the standard laboratory usually takes 5 to 10 business days, with rush options available.

What are your costs for water quality testing?

Basic lab panels start at a few hundred dollars. Full contamination assessments with monitoring wells cost more. Either way, testing is always cheaper than the failure or violation it prevents.

Do I need water testing for a construction project?

If your project involves dewatering, shallow groundwater, stormwater permits, or an environmental site assessment — yes.

Can water quality really affect my foundation?

Absolutely. Sulfate attack and chloride-driven corrosion are leading causes of early foundation and buried-utility failure.