TDI is thrilled to announce that Malcolm Drilling has joined The Dewatering Institute (TDI) as a Company Member. Malcolm Drilling Company was founded in 1962 in San Francisco, California, which remains their headquarters today. Malcolm operates throughout the United States, maintaining a network of regional offices to serve their clients across the country.
Matt Kennedy, Vice President – Director of Dewatering Operations says, “Malcolm Drilling is very proud to become a Company Member of The Dewatering Institute. Malcolm Drilling is one of the largest dewatering contractors in the United States and excited to connect with TDI.
Dewatering:
Malcolm offers complete construction dewatering services, from site evaluation and system design through installation, operation and maintenance. Their incomparable experience, tools, and equipment fleet allow them to install dewatering systems in the most difficult subsurface conditions.
What are Deep Wells?
Dewatering solutions such as deep wells are often the most efficient and cost-effective depending on subsurface conditions. Deep wells are best drilled in soils with high permeability (sands and gravels) as well as in conditions where there are high pumping volumes or heads. It is often necessary to drill deep wells when working with coarse-grained sands, gravels, and cobbles. In the most challenging subsurface conditions, Malcolm has the expertise and equipment to install dewatering systems. Malcolm’s fleet of modern drill rigs and drilling tools allow us to install wells through sands, gravels, cobbles, boulders and rock, as well as under artesian conditions (groundwater under hydrostatic pressure).
Malcolm’s fleet of modern drill rigs and drilling tools allow us to install wells through sands, gravels, cobbles, boulders and rock, as well as under artesian conditions (groundwater under hydrostatic pressure). Deep wells can be equipped with electric submersible pumps (0.5–15 HP), which are typically connected via flex hoses to a common HDPE header piping that leads to the discharge location. These wells are typically installed outside the excavation; however, depending upon the shoring systems, these wells can also be installed and utilized on the inside of a cutoff shored system. Well spacing is dependent upon the subsurface conditions and the constructability, all of which are taken into consideration by the dewatering design and our field expertise.
Vacuum Wellpoints
A Vacuum wellpoint system is a complete dewatering system that consists of a wellpoint pump, a vacuum header, and a number of wellpoint connected to the vacuum header. The wellpoint pump is used to apply a vacuum to a series of wellpoint via a vacuum header. The wellpoint is a two to three-inch diameter self-contained vacuum well composed of casing, screen drawdown tube and check valve installed into a predrilled hole or jetted into the ground, usually no deeper than 25 to 30 feet. The vacuum header pipe provides groundwater removal by suction left of a series of wellpoints or dewatering wells. Finally, dewatering wells are assisted by vacuum in order to improve their ability to remove entrained water, particularly for soils with fine grains.
Vacuum wellpoints are well suited for a wide range of soil permeability’s (fine to coarse grained soils). They are generally 15 to 25 feet deep and constrained by the limits of the vacuum to pull water out of the ground. They typically have a 3-foot length of slotted well screen at the bottom and are most often spaced from 2 to 10 feet on center, depending on the soils type.
Eductor Wells
Eductor well systems are most advantageous when dewatering deep excavations where the volume of water to be pumped is relatively small because of the low permeability of the aquifer. Like vacuum wellpoints, eductor wells are spaced 2 to 10 feet on center; however, unlike vacuum wellpoints, eductor wells do not have drawdown limitations. Installation of eductor wells is similar to vacuum wellpoints but eductor wells can lift water deeper than 25 feet.
In operation, water under pressure from the eductor well pump enters the eductor well through the pressure nozzle and venturi, causing a difference in pressure, which creates a vacuum that draws the groundwater through the well screen and flows up into the body of the eductor well where it is entrained by the pressure water. Both liquids are mixed in the body of the eductor well and are discharged against back pressure up to the ground surface.
What are Artesian Wells?
An Artesian Wells is a well where water rises under pressure, naturally. Groundwater in some aquifers is confined between an upper and lower impermeable soil layer but the aquifer recharge source is located at a higher elevation which pressurizes the groundwater within the aquifer. If the pressure/piezometric level of the groundwater is above the ground surface, this is known as an artesian aquifer or condition. Constructing wells in artesian aquifers is extremely difficult as the groundwater flowing up the borehole towards the ground surface makes installation of the borehole seal at the upper confining layer very difficult. Maintaining hydraulic equilibrium of the borehole (i.e. no groundwater flow) during seal installation allows the seal to cure and eventually hold back the pressure of the aquifer. One way to create hydraulic equilibrium in the borehole is to raise the casing above the ground surface up to a level where the groundwater stops flowing over the edge of the casing. Malcolm has over 6 decades of experience and can handle all types of artesian wells and difficult conditions.
Water Treatment
In many cases, dewatering operations generate groundwater that must be treated in order to properly discharge it. Solids, volatile organics, and other undesirable compounds are often removed during water treatment before discharge. The techniques and methods that Malcolm employs to treat wastewater are capable of being designed, operated, and maintained. Malcolm can also assist in the application process for permits. As a water treatment professional, Malcolm’s experience ranges from industrial wastewater treatment to commercial water treatment to the private sector.
What is Sonic Drilling?
Sonic Drilling is well suited for a wide variety of applications. What sets this technique apart from conventional drilling techniques is the ability to easily adapt to a wide variety of soil and rock types with minimal tooling change. Sonic drilling can perform in the most difficult ground conditions much faster and with the lower vibration and noise disturbance than any other drilling method.
Sonic Drilling uses high-frequency, resonant energy generated inside an automated drilling head to advance a core barrel or casing into the subsurface. As the bit face drills, the resonant energy is transferred along the drill string at various Sonic frequencies. By rotating the drill string simultaneously, the bit face receives even amounts of energy and impact.
The Terra Sonic drilling rigs, we are using are the perfect choice for any urban environment or restricted access work. Due to their compact size and ability to utilize rubber tracks they can even be used indoors. Our fleet of machines installs Micropiles, Tie-Downs, Tie-Backs and Dewatering Wells on the regular basis. We recently added equipment to also offer geotechnical and environmental sampling to our clients. The techniques’ unique ability to provide continuous samples of almost all very difficult to sample soil types in combination with the speed of operation makes them superior to other drilling techniques. We can also perform SPT as well as ground water sampling or use our machines to core concrete with extreme speed to great depth.
Sonic Drilling Specification & Capabilities
- Continuous sampling in all ground conditions
- Diamond coring of HQ and PQ sizes
- Drilling depth of up to 800ft with borehole diameters of 6 to 12in
- Able to drill in angles up to 45°
- SPT and Ground Water sampling
- High verticality drilling tolerance (<1% at depths over 100ft)
- Very cost effective, due to low diesel consumption and no need for support equipment
- Outstanding flexibility due to compact footprint
Download the Malcolm Dewatering Brochure below:
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