Dewatering is when water – namely in the form of groundwater – is extracted from soil, rock or other geologic material using methods such as cuts/sumping and pumping or wells/wellpoints and similar are used to literally cut off and / or remove groundwater from subsurface materials it accumulates in. This allows for required excavation work to proceed and control hydraulic forces.
Site Dewatering from Professional Consultants
Effective understanding, accounting, and control of water are critical to the success of a development. The majority of failures and liability in geotechnical / engineering geology are in some degree caused by or exacerbated by water. Improperly accounted for – subsurface structure and groundwater can have incredible influences on constructability, costs, and performance on excavations and construction that bears on or extends into. This includes slopes, foundations and structures, and importantly – offsite properties and improvements
Effective understanding of water, particularly groundwater, must be combined with a strong understanding of the engineering aspects of the geologic materials and structures associated with it. This not only includes understanding what is under a particular site itself, but the surrounding properties that may be influenced by the work, the nature of occurrence and recharge of the groundwater, and any ramifications that may occur as a result of the dewatering.
Hand in hand with the engineering aspects of groundwater dewatering are the aspects of the environmental/chemical nature of the groundwater – including presence and handling/treating any hazardous contaminants and the possible effects and fate of its chemistry on discharge areas. Another key aspect is having firmly in hand the jurisdictional permitting and regulatory requirements associated with dewatering and water handling operations.
Need for Appropriate Expertise – As experts in engineering geology and water resources/groundwater, we have seen time and time again that having the right experts on the project can make all the difference between success and failure or future liability. Most conventional engineers and geologists are not experienced in general water mechanics, and even less in groundwater and its control. Even fewer have the third dimension of firm understanding of the intrinsic and regional structural geologic aspects that control the engineering behavior of both the groundwater and the earthwork and foundations.
What sets the G3SoilWorks team apart from the rest is we have a love for science, and in particular, structural geology, rock and soil mechanics, and water that starts at the top. We understand the problems and challenges, and know how to solve and meet them. We are not put off by difficult projects, or thinking out of the box for unique solutions. We are experts – legally recognized as such.
In order to be a water extraction / dewatering / drainage expert, you must have a firm understanding of:
The engineering geologic setting;
The hydrologic setting;
The influencing regional and local geologic structure;
The engineering character of the surrounding properties and their sensitivities;
G3SoilWorks prides itself in expertise with all of the above. Our background includes being associated with major water projects and water entities, such as Imperial Irrigation District, Bureau of Reclamation, and other water authorities. We have also been associated with as engineer of record on major dewatering operations associated with the Elsinore Backbasin, and for hotels, large developments and similar all through southern California.
Understanding Groundwater, Seepage, and Soil
Groundwater – namely, its mechanics and occurrence – is one of the most poorly understood aspects of civil engineering and engineering geology to the majority of design and construction professionals. Groundwater is a form of subsurface water that differs from seepage and soil moisture in that it is typically in a form that is organized as a body and is available to flow to wells and similar. These bodies occur in geologic materials that are porous, and that the pores are interconnected and can communicate such that buildup, storage, and flow of water can occur. These geologic materials that serve as the vessel for groundwater are known as aquifers or aquiferous. Common examples of aquiferous materials are sand, gravel, uncemented sandstone, fractured/jointed rocks, and rocks units such as karst limestone/marble and porous volcanic rocks that have large interconnecting void networks. Groundwater occurs in multiple forms that are dependent on the structural/depositional nature of the geologic materials present, and the nature of how it is recharged and drained. Groundwater is confined and constrained by materials of low permeability – known as aquicludes and aquitards. These are typically clayey/silty, cemented, or other materials that lack interconnection between voids/pores and do not transmit water very well.
Where groundwater occurs in formations that are “open” and uncapped, the water fills the aquifer to a level equal to its head pressure. This form is known as unconfined – and is the simplest form of groundwater – similar to a tub filled with gravel that water is poured into. The level that the water rises to in the aquifer is known as the water table. Where groundwater occurs in aquifers that are capped or similarly constrained by low permeability materials – they can fill completely, and if recharged from sources of higher elevation head and/or subject to loading, they can become pressurized – meaning their pressure head is higher than their physical head. These types of aquifers are known as confined. Where this pressure is great enough, a well drilled into such an aquifer can allow the water to escape and flow up the well – a condition known as artesian. Where there are leaky portions present in the confining materials, the aquifers are known as semi-confined.
Perched water is a form of groundwater that is more localized, and tends to accumulate on top of low permeable lenses and beds included in an unconfined aquiferious formation above the basement or main water table. The percolating water literally sits – or is perched – on top of these low perm zones. Perched water is common in alluvium and fills. It tends to be limited and transient.
From the above, groundwater may exist in multiple forms at various levels under a site as separate discrete bodies, or as an anastomosing of multiple interfingered bodies.
Seepage differs from groundwater in that it tends to occur as localized individual sources of weakly mobilized water responding to being “daylighted” that can flow from seams and more permeable portions of saturated otherwise low permeability materials, or as localized and limited accumulations of pockets in more permeable materials. In design, seepage is often mistaken for groundwater, particularly in standpipe wells as seepage may drain into a well and accumulate in a well to the height of the seep and give the appearance of being a body, but actually, the materials below the seep level may be impervious, unsaturated, or otherwise not groundwater. Seepage examples include localized weeps and wet spots on excavation slopes.
Soil Moisture is water that is not freely mobile and is held within the pores of a soil by capillarity, cohesion, and other similar forces. This moisture is typically not available to flow to wells or cuts, but may move thermodynamically.
Drainage is where water is provided a means of conveyance away and not accumulate. A common and very troublesome occurrence in construction and development is not properly accounting for drainage, and flooding, hydraulic loading, and waterlogging can develop. Surface water and seeps typically respond to drainage. Proper long-term drainage also keeps seeps and surface waters from accumulating into more organized bodies / groundwater. Drainage typically occurs under gravity means, although pumping or similar may be used to discharge accumulating waters where gravity doesn’t work.
Dewatering Solutions
Due Diligence and Feasibility
Before undertaking any dewatering processes, the land must be appropriately studied and understood. The amount of water present on and under the ground, along with the nature of its occurrence and the character of the materials it is associated with needs to be determined, which then allows the professionals to evaluate what will be needed to drain and control it appropriately.
An engineering geologic / geotechnical report will be drawn up in these initial stages and used throughout the planning process to make informed decisions. To stay true to the design drawn up, the applicable / pertinent engineering aspects of the site must be correctly estimated along with its drainage capabilities and character. It’s important for the dewatering process to be carried out properly, as a lack of proper planning can result in serious problems. Our team understands all these risks, meaning your site will be kept as stable as possible.
Planning and Design
Here at G3 SoilWorks, we can offer you all the advice you need when it comes to planning your dewatering project, as well as help you find the right experts for the job. We have extensive knowledge in this field and are more than equipped to assess any current designs you might have or help you develop new ones that comply with regulatory and safety standards. Dewatering Type and Method Evaluation There are a wide variety of different approaches, means, and methods of accomplishing dewatering. The particular types and their combinations will be determined based on hydrologic conditions, design needs, offsite considerations, and related factors. G3Soilworks enjoys ongoing relationships with a variety of drilling, well, and specialty contractors to assist in finding the right approach for a particular project.
In some cases, it’s also beneficial to monitor the quality and levels of groundwater present before or after dewatering. Before dewatering, this offers insight as to whether you actually need to remove water and what solution would be best to use. However, you may wish to know more about the quality of the water or its chances of reappearance on your site as well, meaning effective monitoring after dewatering could help you prepare for the future.
Construction services
Dewatering can be useful in a range of situations, but here at G3 SoilWorks, we’re well-versed on advising you on dewatering systems in construction.
Oversight of Dewatering Installations and Monitoring
Our team as Dewatering Consultants will be with you every step of the way while your dewatering construction project is being carried out. We’ll always be on hand to offer expert advice, no matter the hurdles you come across.
With our experience lying in both construction and dewatering, we’ll be able to offer even more penetrating insight into how your new structure can be built as efficiently and successfully as possible.
3rd Party Oversight, Water Quality, and Accessibility
We assist with the monitoring and supervision of dewatering projects to ensure their efficient follow-through and smooth operation. As such, we also assess water quality conditions using all technical models available, as well as assessing its accessibility on requested projects and sites as requested, depending on the need and always applying our G3 Method of scientific approach, data collection, and testing.
For Groundwater Management Services, Get in Touch
Dewatering can be a tricky process, even with the best water extraction experts on hand. For those moments when you have a problem you just don’t know how to tackle, we’ll be here. For more information, you can contact us by calling +1 (714) 707-3155, by sending an email to info@g3soilworks.com, or leaving us a message through our contact form.
