Common and Uncommon Observations

Well videos from cameras provide an excellent tool for better understanding downhole conditions.

By Marvin F. Glotfelty, RG

Figure 1. Examples of common observations from well videos: Mills knife perforations that are well spaced (upper left) or poorly spaced (upper right), heavy scale accumulation (lower left), and dropped debris such as cable (lower right).

Numerous techniques are available for us to evaluate water wells such as geophysical logging, aquifer testing, and water quality sampling. However, one of the most widely used and beneficial tools for well assessment is video surveys.

Video cameras have been used for inspecting water wells since they were invented by Claude Laval Jr. in the 1940s. Modern video cameras provide color video and are equipped with both a downward-viewing lens and a sideward-viewing lens that can be rotated 360° to provide complete inspection of the well’s interior.

I’ve reviewed hundreds of well videos over the past four decades and encountered both common and uncommon observations in water wells. Just about all these observations provided helpful insight about the well. Below are some examples of common and uncommon video observations that have been helpful for understanding the overall conditions of assorted wells.

Common Observations in Well Videos

Figure 2. Well structure attributes like the top of well liners are common observations in well videos. The well liner in the upper right has been flanged (orange peeled) to accommodate easy pump installation.

Observations from well videos are helpful for characterizing the well, including the type and condition of perforations or well screen, the extent and characteristics of scale accumulation in the well, and dropped objects or debris in the well (Figure 1). The depth (in feet) being viewed is typically illustrated near the center of the well video.

Well videos also provide information on subsurface structural conditions that may not be otherwise catalogued in the public records of the well such as the perforated interval, the depths of casing patches, depths of casing diameter changes, or the location of well liners (Figure 2).

Figure 3. Bar holes result during casing installation, when the driller suspends the casing from cable that is looped over the ends of a horizontal bar that’s passed through the casing holes. Some bar holes are patched during well construction (upper left) and some bar holes are left open (lower left, showing cascading water).

Video surveys sometimes provide information about the construction methods used by the driller when the well was installed. For example, some drillers prefer to install the well casing by suspending it from a cable sling that’s been looped around the ends of a horizontal bar, rather than suspending the casing from the draw works with casing grips or welded lugs. Installation of well casing in this fashion results in an opposing set of “bar holes” just below each casing joint connection, which may be patched or left open (Figure 3).

Older water wells with steel casing will deteriorate over time, and in many cases the steel casing will eventually develop corrosion holes as shown in Figure 4. The depth and general characteristics of the corrosion may provide clues as to the overall stability of the well as well as the cause of the corrosion (e.g., saline or aggressive groundwater chemistry, oxidation from cascading water, galvanic corrosion at the connection point of dissimilar metals).

A somewhat common observation in videos of older wells is casing failure (collapse). The root cause of the collapsed casing can often be determined by the characteristics of the casing failure (Figure 5).

Figure 4. Well casing corrosion is commonly observed in videos of older wells. A downward view of corroded casing with torch-cut perforations is shown on the left, and a sideward view of a corrosion hole is shown on the right.

Deterioration of a steel casing’s wall thickness can cause the casing to become out-of-round (elliptical), which results in an exponential decrease in the casing’s collapse strength. During installation and subsequent operation of a well, there may be times (such as during cement seal installation or if the
water level inside the well drops far below the corresponding fluid level outside the casing) when the differential hydraulic pressure between the inside and outside of the casing is great enough to cause a U-shaped or hourglass-shaped deformation.

In areas of extensive groundwater withdrawal, land subsidence causes vertical movement of large land masses, so that the dropping of the upper well casing against the stationary position of the lower casing will result in a buckling failure of the casing, with a polygonal cross section.

Uncommon Observations in Well Videos

Figure 5. Collapsed casing examples. Buckled or elliptical casing (left) generally results from aging steel and deterioration; U-shaped or hourglass-shaped casing deformation (center) is typically caused by differential pressure during cementing; and polygonal deformation (right) occurs in areas of land subsidence due to the vertical movement of the earth that buckles the casing. Note that the green color of the right-hand image is an aberration of the old video clip, and does not represent actual conditions.

In addition to the things commonly seen in well videos, we also occasionally encounter unusual observations. These uncommon well video observations are infrequent and sometimes downright extraordinary, but they are nonetheless quite useful to help us understand the subsurface conditions of the well being evaluated.

If a water well does not have an adequate surface seal, it may be invaded by small animals or insects that are seeking a water source or just looking for a safe dwelling. Animal invasion may introduce coliform contamination into the well, and animal or insect habitation of the well is typically evident in video surveys.

During my career, I’ve seen a variety of animals in well videos (some living, some deceased) including rodents, frogs, snakes, and even live tadpole-looking critters that were squiggling around in the sediment at the base of an 80-foot well.

Figure 6. Uncommon video observations may result when animals or insects find their way into a well, such as the beehive in the top images. In other well videos, groundwater flow under non-pumping conditions can be observed when particulate movement results from localized water jets shooting into the well (blue arrows, bottom images).

One of the most impactful insect invasions that can occur in a water well is a swarm of bees (Figure 6, top images), which will not only contaminate the well, but can also be somewhat hazardous to remove.

Uncommon well video observations include water jets that are sometimes seen in wells located in areas with a vertical hydraulic gradient. A vertical hydraulic gradient results from differing static water levels at various depth intervals of the aquifer. The hydraulic pressures at those different depths remain isolated from one another due to the stratification of the geologic layers (such as clay or caliche) that prevent vertical movement of the groundwater.

In addition to the aquifer stratigraphy, the sediment will have some degree of anisotropy (the condition within a single sedimentary layer that will cause fluids to preferentially flow horizontally rather than vertically). The stratigraphy and anisotropy of the aquifer will prevent comingling or mixing of groundwater out in the aquifer surrounding the well even though there are differing pressure heads at various depths.

Figure 7. Different types of scale growth sometimes occur on perforations versus the blank casing wall, which can easily be observed in well videos.

However, once the groundwater enters the well where all the hydraulic pressure zones are connected, the groundwater will flow from high pressure to low pressure. This condition can be observed in some well videos as water jets or flow streams that are rapidly entering or exiting the well. Water jets (Figure 6, bottom images) are easily identified from the movement of floating particulate matter that is being transported by the fast-moving water.

We ordinarily see scale or biofilm accumulations that have been deposited on the surface of a well casing or screen in a uniform layer (Figure 1, lower left image). However, deviations from the norm can happen with biochemical deposits, and we occasionally see localized scale accumulations on the well’s perforations that are different than the adjacent scale on blank casing (Figure 7).

In unusual cases, we also sometimes see stalactitic scale that forms in long tube-shaped columns. When the size of stalactitic scale columns are small, they have a somewhat root-like appearance (Figure 8), although plant roots are not documented at depths greater than about 230 feet (https://greenpacks.org/what-plants-have-the-deepest-roots).

Figure 8. Stalactitic scale growth with plant root appearance, at depths of 308, 425, and 474 feet. The tube-shaped scale deposits look like roots, but they are almost certainly unrelated to plants.

One of the most unusual and concerning instances of debris removal from a water well that I’ve ever experienced began with a well video survey I reviewed back in 1988. At that time, my firm had been hired to oversee the abandonment (decommissioning) of 44 inactive wells on a large farm that was being purchased. The buyer of the land did not want to take on any environmental liability, so each unused well was to be cleaned out to its original depth and then abandoned in accordance with State of Arizona regulations.

One particular well was rumored by locals to contain all sorts of medical debris and was the topic of many ghost stories and scary tales. This was a 20-inch-diameter × 578-footdeep well that locals called the “Doctor’s Well” (read more about it in the November 2022 issue of Water Well Journal. The initial video
of the well indicated debris fill at a depth of 134 feet, so we began the process of cleaning out the well.

During the next few weeks, a substantial volume of material was removed from the well down to a depth of 510 feet where sediment fill was encountered. The debris that was removed from the well was contained in 55-gallon drums and logged by a field hydrologist (Figure 9).

The documented materials that were bailed from the well included farm accounting documents; a file cabinet drawer filled with pages from medical textbooks and medical records (some with the doctor’s name on them); hypodermic needles and syringes; glass medicine vials and pill capsules (some full); a fire extinguisher; a camera; an oxygen regulator; a pressure gauge; and part of an Arizona liquor license! All the items had apparently been thrown down the well by an unscrupulous medical doctor, and after years of doing so, there was a total of about 30 cubic yards of debris in the well.

The debris was bailed from the well where we separated the solids and liquids with a shale shaker and used a very long pair of tongs to avoid direct handling of the medical waste. Since medical sharps had been encountered, we subcontracted a medical doctor and an industrial hygienist to provide recommendations
on the handling and disposal of the waste material. The presence of syringes and needles classified the debris as infectious waste, and sampling of the waste also indicated concentrations of polychlorinated biphenyls (PCBs) that further categorized the debris as a hazardous waste.

Figure 9. Excerpt from 1988 field notes recorded during the cleanout of the “Doctor’s Well” in Arizona.

The debris was eventually removed and contained in drums for proper disposal, and the “Doctor’s Well” was decommissioned in accordance with state regulations.

The Arizona Department of Environmental Quality had requested a report on the well cleanout and abandonment, which I delivered by hand. By the time I returned to my office, a representative from the Attorney General’s office was holding on my phone waiting to talk about filing a lawsuit against the unprincipled doctor. It turns out the doctor’s license to practice medicine had long since expired and he no longer saw patients or lived in the area. The damage he’d done had been remediated, so no further legal action was taken.

Figure 10. Subsurface hallway constructed with arched masonry, which was connected to an old municipal well. The purpose of the subsurface room was reportedly to dewater a historically swampy area for agricultural development.

The well cleanup resulted from an uncommon well video that revealed an unusual situation, but fortunately, the mess was discovered and cleaned up.

About a decade later, while working on another project involving the abandonment of several municipal wells, I once again encountered an uncommon well video that clarified some very unusual subsurface conditions in a well.

At the start of a pre-abandonment well video, we anticipated seeing the common attributes of a 200-foot-deep agricultural well. However, at a depth of about 15 feet, the well casing ended and the camera entered a subsurface hallway constructed of arched red bricks (Figure 10). The roof and floor of the subsurface room were open to the well, so this underground hallway had been purposefully constructed in association with the well.

We initially thought this must be some sort of bomb shelter or escape route, but since this subterrestrial room was previously unknown—even to the municipal well owner—the local historical society was contacted to seek answers. It turns out that in the early days of agricultural development in this area, a shallow perched aquifer was causing swampy conditions, so the shallow aquifer needed to be drained. The underground hallway was installed as part of a collector system to dewater the area.

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Both common and uncommon observations may be encountered in well videos, but a consistent characteristic of essentially all video surveys is that they provide an excellent tool for us to augment our understanding of downhole conditions.

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Marvin F. Glotfelty, RG, is the principal hydrogeologist for Clear Creek Associates, a Geo-Logic Associates Co. He is a licensed well driller and registered professional geologist in Arizona, where he has practiced water resources consulting for more than 35 years. He is author of The Art of Water Wells (NGWA Press, 2019) and was the Groundwater Foundation’s 2012 McEllhiney Lecturer. Glotfelty can be reached at mglotfelty@geo-logic.com.