Monday, July 31, 2017

Dug Well- Rust Colored Water after Rain Storms

We had quite the storm pass through here yesterday. Frankly after heavy rains I always get a pile of questions about rust colored water. Here is a problem that showed up in Spring 2016. I just heard from the homeowner last week with another concern so I was reminded of his problem. (It’s edited for clarity.)

“I have had a problem with my 38 foot deep 2 foot diameter dug well in rural Spotsylvania County that I have been fighting for the past 9 years...The water from the well will stay brown for about 2 weeks after a series of heavy rainstorms. Consequently, we always use bottled water during that time and wait for things to clear up. I have regularly tested the well after things have cleared up over the years by using the WaterSafe test kit and have never noticed bacteria. (I have never tried it when it was brown though).
The water entering the house is pre-filtered by a pleated 10 inch 50 micron filter. When the heavy rains start, I have (with some success) put in a 5 micron carbon filter in its place. This seems to help when things aren’t so bad, but it doesn’t do very much when there are storms going on for days on end like the ones we had. This only happens once or twice a year. After the mineral earthquake, the problem stopped for nearly 3 years! I’d welcome your thoughts.”
photo from J. De Jesus

The image above shows the outside of the well. The 1992 Water Well regulations for Virginia state “Shallow wells are not desirable from a public health standpoint and shall not be used for new construction, except when deep wells attempted have been nonproductive, as it is normally possible to obtain sufficient water from a deep well.“ Existing wells were grandfathered under the regulation.

Thirty-eight feet is a very shallow well and likely to be impacted by surface infiltration, and drought. Typically rain water and snow melt percolate into the ground and the deeper the well the further away is the water origination and the older the water. The groundwater age is a function of the depth of the well, the geology of the area, the precipitation, recharge of the aquifer and pumping rates of the aquifer that control the rate of flow of water to a well. The age of the water in an aquifer provides insight into the likelihood of contamination from both anthropogenic and natural sources. Very young groundwater that has recently infiltrated into the aquifer is more vulnerable to contamination from human activities near the land surface than older, deeper groundwater that has had more time to be filtered by soils. Old groundwater, however, is not necessarily free of contaminants. The older groundwater can contain naturally occurring chemical elements and contamination from years past. The land surface through which groundwater is recharged must remain open and uncontaminated to maintain the quality and quantity of groundwater.

The fact that well owner states that when he tested the water was free of bacterial contamination and that the problem cleared up for a few years after mineral earthquake does suggest that the problem might be infiltration of Virginia red clay carried in the very young groundwater during storms. The most common type of observed ground-water response to an earthquake is an instantaneous water-level fall or rise and can occur near or far from the epicenter of the quake without significant change to the rock formation. Recovery to the pre-earthquake water level can be so rapid as to be almost unnoticeable, or it may take as long as several days or months. Water level changes can be large enough to make a well flow to the land surface, or render a well dry.

The shaking associated with an earthquake may cause sand or clay fines to plug a well screen, and thus reduce the volume of water that can be pumped. Conversely, the shaking can dislodge sand/clay fines plugging a well screen and cause an increase in the volume of water that can be pumped from the well. In Virginia where well casings typically extend only 50 feet below grade or in this case of a very shallow well, the shaking or oscillation of the earth may dislodge sand or dirt within the water table that can be captured by the pump. In in this case the looser dirt within the water table might have been flushed so that for a few years there was not enough dirt to be carried by heavy rains. 
photo from J. De Jesus
 Nonetheless, the typical sources of rust colored water cannot be discounted as a cause of the problem. After rust in the household fixtures there are five causes for well water to be discolored or brownish: surface infiltration, well collapsing or water level dropping, iron – iron bacteria and/or manganese in the water, pump system or well casing rusting and worst of all contamination from a nearby septic system.

The most likely causes of dirty looking water after heavy rains is surface infiltration and shallow groundwater in a shallow well, but contamination from a failing septic system is also possible and should be investigated an monitored for. The bacterial test can help confirm whether the problem is septic. I would recommend taking a water sample to a local certified laboratory, and have the water tested for coliform bacteria and if positive e-coli and fecal coliform bacteriaat the very least. However, to further diagnose the problem and monitor the well the water should be tested regularly for: iron, manganese, nitrate, lead, arsenic, fluoride, sulfate, pH, total dissolved solids, hardness, sodium, copper, total coliform bacteria and E. Coli bacteria. Also, considering how shallow the well is an occasional look at pesticides might be prudent.

Filter cartridges for sediment removal are rated in microns. As you know, the micron rating for a water filter is a way of indicating the ability of the filter to remove contaminants by the size of the particles. A filter that is marked “5 microns” has some capability in capturing particles as small as 5 microns. However, there is no one accepted method to measure and describe the size of particles that a filter can capture or the total amount of particles that the filter can hold. Filter micron ratings for water are usually Nominal or Absolute. For sediment removal, Nominal rated cartridges are most common. Absolute ratings are needed for example, in removing Giardia, a type of parasite, when it becomes important that the filter cartridge absolutely must be rated at 1 microns. A Nominal Micron Rating (NMR) usually means the filter can capture a given percentage of particles of the stated size. For example, a filter might be said to have a nominal rating of 90% at 10 micron.

The breakthrough you are experiencing could possibly be resolved by having two or three filters in series, a 50 micron followed by a 25 micron followed by a 5 micron; however, I have a basic concern that there is the possibility that your well could be impacted not only by bacteria but by parasites and spores that have the potential to be fatal in vulnerable populations. Though I would encourage you to drill a well at least 100 feet below grade to ensure the health of your family, surface water can be treated. You need a series of filters meticulously maintained to reliability remove the discoloration, a series of two or three should do it. (This will impact your water pressure that you may need to boost.) Make sure you match the flow to the capacity of the filer. Then after the water is clear you need to disinfect using a using a UV light.

Finally, you will need a point of use filtration system for any water that is likely to be drunk because of the potential for cysts, parasites etc. Giardia is a fairly common microscopic parasite that causes diarrhea. Once an animal or person is infected with Giardia, the parasite lives in the intestine and is passed in feces. Because the parasite is protected by an outer shell, it can survive outside the body and in the environment for long periods of time extending to months. Millions of Giardia parasites can be released in a bowel movement of an infected human or animal. Human or animal waste can enter water through sewage overflows from flooded septic systems, polluted storm water runoff, and agricultural runoff. Wells may be more vulnerable to such contamination after flooding, particularly if the wells are shallow, have been dug or bored, or have been submerged by floodwater for long periods of time.

The CDC usually recommend boiling water, but that may be impractical unless you are sure that the water is impacted. An alternative to boiling water is using a point-of-use filter. Not all home water filters remove Giardia. Filters that are designed to remove the parasite should have one of the following labels:
• Reverse osmosis,
• Absolute pore size of 1 micron or smaller,
• Tested and certified by NSF Standard 53 for cyst removal, or
• Tested and certified by NSF Standard 58 for cyst reduction.

There are now available on the market some carbon block filters which takes care of cysts and some chemicals and are certified by NSF Standard 53 0r 58. I am always interested in your problems. Please use email to ask questions. 

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