Fisher Environmental's associated hydrogeologists have the experience and skills to solve complex design problems.  Water resources evaluation includes services related to the identification, evaluation, remediation and protection of ground and surface waters.

Fisher Environmental recommendations are based on a site-specific exploration program, a comprehensive understanding of the site subsurface conditions, and decades of professional experience.  We have built a reputation for responsive and practical service and quality.  We provide cost effective solutions for all your groundwater investigation needs.

Groundwater is stored naturally below the earth's surface.  Most groundwater originates as rain or snow that seeps into the ground and collects.  As water seeps into the ground, it settles in the pores and cracks of underground rocks and into the spaces between grains of sand and pieces of gravel.  In time, the water trickles down into a layer of rock or other material that is water tight.  This water tight zone collects the groundwater, creating a saturated zone known as an aquifer.  Drilled or dug wells are constructed into these aquifers to explore aquifer conditions, extract water for various needs or control groundwater flow.

Aquifer Classification

Two broad classes of drilled-well types may be distinguished based on the type of aquifer which the well is completed in:

• shallow or unconfined wells are completed in the uppermost saturated aquifer at that location (the upper unconfined aquifer)
• deep or confined wells, which are sunk through an impermeable stratum down into an aquifer which is sandwiched between two impermeable strata (aquitards or aquicludes);  the majority of confined aquifers are classified as artesian because the hydraulic head in a confined well is higher than the level of the top of the aquifer and if the hydraulic head in a confined well is higher than the land surface it is a "flowing" artesian well

There clearly are many cases that fall in between these two end-members; often unconfined wells may be very deep (what is often called a shallow well can be over 150 m deep) and many times wells are completed across all aquifers from their top to their bottom (especially agricultural or industrial wells), being open to both unconfined and confined aquifers.

Types of Wells

For today’s hydrogeological assessments, drilled wells are the standard practice.  Drilled wells are equipped with a factory made case, typically steel (in air rotary or cable tool drilling) or plastic/PVC (in mud rotary boreholes or dry augered boreholes, also present in wells drilled into solid rock).

At the bottom of wells, based on formation, a screening device, filter pack, slotted casing, or open borehole is left to allow the flow of water into the well.  Constructed screens are typically used in unconsolidated formations (sands, gravels, etc.), allowing water & a percentage of the formation to pass through the screen.  Allowing some material to pass through creates a large area filter out of the rest of the formation, as the amount of material present to pass into the well slowly decreases and is removed from the well.  Rock wells are typically cased with a PVC liner/casing and screen or slotted casing at the bottom, this is mostly present just to keep rocks from entering the pump assembly.  Some wells utilize a 'filter pack' method, where an undersized screen or slotted casing is placed inside the well and a filter media is packed around the screen, between the screen and the borehole or casing.  This allows the water to be filtered of unwanted materials before entering the well and pumping zone.

Two additional broad classes of well types may be distinguished, based on the use of the well:

• production or pumping wells, are large diameter (> 15 cm in diameter) cased (metal, plastic, or concrete) water wells, constructed for extracting water from the aquifer by a pump (if the well is not artesian)
• monitoring wells or piezometers are often smaller diameter wells used to monitor the hydraulic head or sample the groundwater for chemical constituents; piezometers are monitoring wells completed over a very short section of aquifer whereas monitoring wells can also be completed at multiple levels, allowing discrete samples or measurements to be made at different vertical elevations at the same map location