Thursday, December 23, 2010

Groundwater for Irrigation


If you (or someone you love) are considering drilling a well for irrigation, please save yourself some money and collect some empirical information about your water supply. The only way to understand it, is to conduct some kind of "stress", "aquifer", or "pump" test on the water supply. There are number of sound reasons to conduct some kind of test on the well. But the number one reason I tell my clients is that it protects their investment.

As an example, look at the photo above. It was proclaimed that the well yielded "100 gallons per minute (gpm)". Really? For how long? "...well, for the 10 minutes we "blew" it out of the hole". Hmmm, ok.

Why spend $10K to $20K on a well, pump, piping and irrigation system to find out later that your 100 gpm well is really a 10 gpm well. The water is "the dog that wags the tail" for the entire enterprise; yet, I am amazed at the number of intelligent people who ignore the need to collect at least some minimum data regarding the capabilities of the aquifer beneath their feet.

I had a client who required 7500 gallons of water twice a week for his irrigation needs. He decided that before he invested an enormous amount of money for his irrigation system that he would have me conduct a limited pump test.

We first conducted a "STEP" test on the well. A STEP test is a "pre-test" for the main pumping event and is conducted to determine a pumping value for a longer period pump test. You start pumping the well at low rate- measure the drawdown and "STEP" it up after it appears it will hold. Here on the right is the graph of time vs drawdown for STEP test on this well. In this case we started at 5 gpm. This is a semi-log plot and it is clear that the well could handle 5 gpm (at least for awhile). So, we "stepped" up to 10 gpm. And the curve began to adopt an asymptotic shape. All good. Then we jumped it to 17 gpm. And lookie there!! It held steady at around 50 feet then the "angle" got a "little" steep. So steep that we needed to slow down!!! WHoaaaa Nelly!! So, we stepped back to 11 gpm and called it good for the day.

So, we allowed the well to rest from this activity and went back to work on the Alberene Soapstone patio in my yard (here on the right). This soapstone is a Proterozoic-age ultra mafic rock that was recrystallized by metamorphic processes. These emplacement "pods" make up a portion of the Lynchburg Group of rocks in central Virginia. Anyway, we went to quarry and bought several truckloads of scrap ($75/load)-hauled them back home and cut them with a wet saw that belongs to Terry Waggener (seen in previous post). He is a lengendary stone mason who knows more about geology than most graduate students (certainly more than me). The retaining wall in the background was made from precambrian-age granite gneisses, cambrian-age catoctin greenstones and the base layer were rocks from the arkosic sandstone/quartzites of the Lynchburg group (similar age as the soapstone).

Back to the test: we
returned to the property to conduct a limited withdrawal of the well only to find everything frozen up and had to spend several hours unthawing the pipes.

Sunday, December 12, 2010

Petroleum Storage Tanks and The Virginia Reimbursement Program

The state of Virginia operates a program that reimburses homeowners and businesses for expenses of cleaning up legitimate tank leaks that are considered a threat to the environment or human health. Please follow the link on my website to learn more about the program (VPSTF). Most of us (tank owners) will have no reason to suspect that our tanks are leaking unless our fuel bills increase unexpectedly or if they come to the attention of professionals hired to screen environmental threats. In the picture to the right is my pal, Terry, posing next to an underground storage tank with an auger in his hand. The fill pipe is sticking up out the ground to the right. True North was hired to determine if there was any evidence to suggest that the tank had leaked. The Tank Fund is there because it is expensive to clean up spills from these leaking tanks. Anyone buying gasoline in the state of Virginia contributes (unwittingly) to this fund. It has made it possible for homewoners to rectify environmental hazards on their property and in so doing protecting their real estate investment. And the homeowner is only
out $500 - and sometimes less-. The reason for this is that environmental consultants are eager to perform this work and will usually waive the $500 fee just to have the work (yes, including us!!). A whole industry has sprung up that represents the interests of the homeowner (one hopes) and conducting the cleanups and working with DEQ to make sure the job gets done.


We recently were hired to conduct an environmental screening of the property above. A part of this work included soil around a buried gasoline tank. Field observations and laboratory analysis indicated that the soil was clean. After the property was purchased the owners hired True North to supervise and document the removal of the gasoline tank. Everything looked good and the tank removals proceeded swimmingly. For those interested heres a video of a portion of the tank removal. PLease forgive the language- we're just a bunch of unrefined good 'ol boys- so please excuse the profanity.....
video

Sunday, July 25, 2010

Water Budget $$

Recently I have been involved in finding groundwater for some rather interesting rural residential projects. I have found that these projects have some interesting things in common: these are expensive homes-in the $1,000,000 to $10,000,000 range, they are built on hill top landscape positions, they will all require water to irrigate the landscaping, water for fire protection, and plentiful water for the home (including high pressure (psi) and an acceptable flow).

Another thing they have in common is that they have all budgeted somewhere between $5,000 and $10,000 for water. This number includes drilling a well, installing the pump and wiring and piping it to the house.

One last thing they have in common is that they have randomly picked a spot and drilled 600 feet (they budgeted for 300) at $10/ft and have hit nothing but rock (we call them "dusters"- yes, I've been involved with a few myself-but that's for another blog...). There's some dust from a drill rig below....!!

So, their budget is blown, everyone is freaked out and then they call the geologist. What to do?

I ask the following question: How much water do you need? The usual answer is "as much as you can get". That's the wrong answer. The accurate answer to that question will drive the amount of effort for a proper investigation and the commitment from the client and the hydrogeologist. The answer to that question requires someone to talk to the irrigation guy, the engineer designing fire protection, the architect, etc. Will there be a pool, jacuzzi, hot tub, lots of overnight guests, guest houses etc., etc..?

If I can get an accurate idea of the water consumption (you wouldn't believe how difficult it is to get an answer to that question...) then I can plan a budget for the investigation. In the photo below is an example of what 50 gallons per minute (gpm) looks like-

I have come to the conclusion that people don't plan for water- they take it for granted.-They pay close attention to the foundation, to the interior and exterior design, extraordinary amount of time discussing the details for lighting, color of the fabric, the furniture, the security systems, etc, etc. I believe it is ingrained in our culture (at least here in eastern North America)that water is free- you drill a hole and water comes out of the ground. But what I have learned is as the population increases and more land is being turned into estates, or modestly built homes for that matter, all the historical precedence goes out the window for two main reasons: (1.) people want to build on hills and consequently need their source water close by (another blog-another day) and (2.) they use way more water than usual and folks want high pressure water systems (like they have in town) and a lot of flow.

So, the geologist goes to work (if they gave up on one well...recently I was called after five wells were drilled and $25,000 had been spent-we got it on the first well but that is a story for another blog) and depending upon the size of the property, the character of the bedrock, the geometry of the fracture and joint patterns and the proximity of accessible potential water zones (PWZs)- the client could spend $5,000 to $10,000 on an investigation before drilling occurs. That number is always a surprise because the project is in full tilt (they're pouring the foundation by now....)- the budget is being violated and everybody is still freaked out because they have no water and it goes against the common idea that water should not cost money (especially paying for a geologist-after all, aren't dowsers free???).

The photo below is an exposure of an early proterozoic-age meta-gabbro, amphibolite or diabase (you choose)...the cool thing is that this rock intruded into the surrounding granite and is so brittle and full of fractures that it made this region of a project site an excellent place to start looking for water- otherwise, it's just an outcrop of rocks that looks like something out of the "Lord of the Rings", right...?


The point of this blog is to encourage my builder friends (and anyone else) to consider adding a line item for groundwater investigations for these large estate/homes. If you budget $10,000 for an investigation (0.1% of a $10M budget....i think (math goes against my grain...)) before you start drilling then everyone knows what to expect, anxiety levels are reduced and you will likely save money by limiting the number of wells drilled- the fact is the largest line item in groundwater exploration is the drilling of the wells- not what you pay the geologist.

Friday, April 30, 2010

Greenland

A glacier from the sky and from the land of glaciers: Greenland, or Gronland. They move a lot of rock and water and carve landscapes- if you blow the picture up you can see that the cliffs in the background have a reddish hue. This is the bedrock- I believe these rocks to be the un-metamorphosed meso-proterozoic sediments of the Thule Basin- they also contain volcanic/basic sills- i have pictures that i'm going to post.

Ok, backing-up,,,i traveled to Greenland with Malin Jennings (here she is on the left-so very happy to be north of the arctic circle!!!) who has been studying the effects of climate change on the people, culture and environment of Northwest Greenland for the past 8 years. A dynamo of a woman who I have known since the 1960's. Please visit her website http://www.aujaqsuittuq.com/ to read first hand all the work she has been doing in this regard.

Getting back to the geology of northwest Greenland, the paper/image on the left was written in 2007 (??) and published by the Government of Greenland on the Mineral Potential of the Thule Basin- Just to be clear- I am not a mineral or oil prospector- while these kinds of papers are written to document the potential for mining minerals, etc they are good resources for finding out what in the hell is going on with the geology in a place like northwest Greenland (or Virginia for that matter- many of the publications I rely on are from the Division of Mines and Minerals).

So, this group of rocks are part of the Thule Supergroup- the rocks exposed on the cliffs north of Qaanaaq (and in the picture from the sky at the top of the page)could be quite old- meso to neo- proterozoic-. This quite a time range -1.6 billion to 520 million years ago-. I'm guessing that since these are not metamorphosed, they are not 1.6 Bya.....i just don't know yet. Anyway, here's a picture of a rock on the slopes above Qaanaaq; this rock is small- it's about 7 inches high (you can pick it up with one hand) but looking closely (blow it up) you can see the wavy boundaries between the layers of sand and silt- this SUGGESTS it was deposited in a near shore or inland flat environment- the red color MIGHT indicate us that enough oxygen was present to oxidate the available iron (Fe) thus imparting the reddish color. A red sandstone.....a beautiful specimen-The specimen is too small to really tell me much else- the wavy structure within the rock hints of aeolian (wind blown) origin- but I am waxing romantic and really just speculating. One would have to observe it in an outcrop to say anything other than it's a red sandstone that may have been deposited in a subaerial environment- There is some question regarding the red color- the rocks they were eroded from contained a large % of iron and it is possible to get a red sediments from a reducing environment-IF there is little in the way of organic material AND the parent rock was rich in Fe. There are geologists who study this stuff who know way more than me about environments of deposition- perhaps they'll read and comment !

The picture to the right was taken by me in the vicinity of where the red rock lay- the view is to the south across the fjord (Murchison Sund)- the settlement at the base of the hill is Qaanaaq, the mountains in the foreground are about 26 KM in the distance. I have not figured out how to link my GoogleEarth placemarks into the blog, but if one is interested "where on earth" this place is type "Qaanaaq, Greenland" into your GoogleEarth thingy.

On the left is map of Greenland (thanks to Destination AVANNA)- and you can see Qaanaaq (the most northerly palindrome in world) in upper left portion of the figure.

The picture of two beautiful Thule women. were taken of a photograph within the museum at Qaanaaq which may have been taken by Peary during his stay at Thule (Qaanaaq)-perhaps in the 1890's. To this day there are residents of Qaanaaq with the last names of Peary and Henson (Peary's able right-hand man).


I think I am safe to say that the rock pictured above is from the lower part of the Qaanaaq Formation (one would not have to be a geologist to come to this conclusion, eh?) - a fining upward sequence of deposits containing crossbedding and ripple marks and encompassing alluvial plane to marine shorline (braid plane to tidal) environments- like the one shown here (stolen and used without permission from the brilliant professor of geology at James Madison University, Lynn Fichter). In this particular case we are focused on the near shore environments (towards the left side of the diagram) I read a paper last night that puts the age of these sediments in the neighborhood of 946 million years ago (MYA)....that is old ! The unit itself includes grey siltstones and carbonates in the upper portions- i found a few specimens of each. What is enjoyable is the story the rocks tell. The climate and environment (and location) were entirely different then what it is now. Just explode that graphic and look at the model of deposition !!