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Posts Tagged ‘Groundwater’

USGS drilling new groundwater measurement well in San Pasqual Valley

Posted by George J Janczyn on February 1, 2013

As part of its wide-ranging groundwater studies in San Diego County, the United States Geological Survey (USGS) San Diego Hydrogeology Project is drilling a new well in the San Pasqual Valley.

Under the direction of project chief Wes Danskin and in coordination with the City of San Diego, the drilling activity is located along SR78 just past Cloverdale Road (at the yellow pushpin in the photo below):

SanPasqualUSGS1a

Or, as seen in a broader context with two other existing wells at Santa Ysabel SDSY and Lake Hodges SDLH (near I-15) marked with green pushpins. Click images for larger version:

USGSSanPasqual2a

The Cloverdale well design is more complex than other San Pasqual sites. Mr. Danskin explains:

WELL SITING

The well was sited to measure the groundwater flowing out of the Cloverdale tributary valley into the San Pasqual Valley. The well was situated as close as possible to Cloverdale Creek so that well data can also be related to surface water leaving Cloverdale and entering the main San Pasqual Valley.

The well needed to be situated so that it was between two hard rock outcrops to ensure the shallow well would sense the alluvium and have enough alluvium to sense; we got a bit lucky in this regard.

The well needed to be as far from the road and bridge as possible, just in case Caltrans decides to widen the bridge or road some decade in the future.

DRILLING

We needed to get a core in the weathered and hard rock zones to prove we are in them, respectively. Then to provide undisturbed samples that can be used later for mineralogy and testing of chemical properties. This aids in understanding water quality data, and in predicting the effect of water-quality changes.

WELL DESIGN

The basic ideas are:

Grout the upper 20 feet so that no water goes down the annulus.

#3 well – In the alluvium, senses the water table

#2 well – In the weathered hard rock (granodiorite), spans the zone between the more weathered and less weathered zones. The weathered granite should have less transmissivity and a lower storage coefficient than the alluvium.

Pumping wells likely affect the weathered zone as much or more than the alluvium. This is what we see from the SDSY well.

#1 well – In the hard rock; split into a 1a and 1b, for upper and lower zones, each located near fractures. They are separated by blank casing and grout in the annulus, so that we later can go in and sample each zone, and install a separate water-level monitoring device (via a packer) in the lower zone to see if the pressures are similar to zone 1b.

Data from SDSY suggests that the alluvium, weathered, and hard rock all are depressurized by the pumping. I would have expected the deep, hard rock zone to have elevated pressures and be less affected than the weathered zone. This is only slightly true. It is possible that this impression is partly caused by our well construction design, so Cloverdale SDCD is to test that concept.

The fractured hard rock may have different water transmitting properties than the weathered granite.

Well #1 is a 3-inch diameter PVC well so that we can later go in with the Electromagnetic (EM) tool and measure changes in salinity with depth. I suspect that San Pasqual Valley over the next decades will become more and more saline, and that eventually the water will become too salty for most agriculture. The valley then might evolve to more of an animal based area.* The EM testing will allow us to quantify this salination. The SDSY well shows that the salination so far is mostly in the upper zone.

Photos of shaker and sieve cuttings:

Shaker
Sieve

NEXT STEPS
Most of the well installation will be done by Friday (today), well development will be Saturday, and equipment will likely move offsite Sunday.

Then, more well development via a compressor; water quality sampling for a large number of constituents; slug tests to measure the hydraulic properties of the different formations; description of cuttings for the CA well report and for San Diego well data report #2; installation of a vault, water-level sensing equipment, and satellite link; updating website with data and photos; and taking a nap.

Photos and project details are courtesy of Wes Danskin.

Wesley R. Danskin
Research Hydrologist
United States Geological Survey
4165 Spruance Road, Suite 200
San Diego, CA 92101
wdanskin@usgs.gov
858-663-6832

______________________________

* On the subject of San Pasqual Valley gradually becoming more saline, I asked Mr. Danskin “You said you suspect the valley may eventually become too saline for most agriculture. Would that be because of agricultural irrigation using imported water that’s quite salty?” His response (please note these are his observations and not an official USGS conclusion):

I would say the issues are:

1. Irrigation return flow; recycling water and accumulating salts in the upper soil; groundwater system. Farmers have indicated to me that they are aware of the increasing salt content and it is affecting their agricultural decisions.

2. Lack of outflow. Near-surface ground water would otherwise have the ability to cleanse the system occasionally by removing salts and discharging to streams that would flow to the ocean.

The natural hydraulic gradient in the lower part of the basin, near Interstate 15, would have been from bottom to top, pushing salts to the surface, then into a stream, then to the ocean. A system without a natural outlet to the ocean (e.g. Owens Valley), tends to accumulate salts in the downstream area, and they just accumulate, eventually looking like a salt lake. The discharge from Lake Hodges mitigates this to some degree, but not as much as an un-dammed system.

 

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San Diego Formation: new USGS deep monitoring well progress report November 2011

Posted by George J Janczyn on November 7, 2011

On October 20, USGS under contract with the City of San Diego began operations on a new deep monitoring well in the Chollas Creek vicinity near the intersection of Home Avenue and Federal Blvd. The well is the latest in a series of multiple-depth wells being drilled in selected areas of four coastal river basins for the San Diego Hydrogeology Project.

The primary objectives of the project are to develop an integrated, comprehensive understanding of the geology and hydrology of the San Diego area, focusing on the San Diego Formation and the overlying alluvial deposits, and use this understanding to evaluate expanded use of the alluvial deposits and the San Diego Formation for recharge and extraction.

Project Chief Wes Danskin writes about the latest developments:

November 1:

1. Hit the Otay formation, at 648 feet. Check out the photos of cuttings below; bet you can pick it out too. And we hit it within about 60 feet of where I thought.

And very pleased with my newest idea: poker chips to identify the formations; I can write on them, and they don’t dissolve or fly away like post-its.

The poker-picks you see here are: the San Diego formation identified via shells; and the Otay formation looks like Otay.

Each square sample box is 10 feet of drilling. The rectangular boxes indicate where we took a core.

Photo 1 below is 0-240 feet.

Read the rest of this entry »

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USGS set to drill next deep monitoring well in San Diego

Posted by George J Janczyn on October 15, 2011

WHO
The United States Geological Survey (USGS), in cooperation with the City of San Diego, will begin installation of the next deep monitoring well site. The drilling and well installation is being done by USGS Research Drilling Unit, which aids USGS scientists throughout the western United States. The USGS is part of the Department of the Interior, and is the primary federal agency charged with investigation of earth resources. The USGS does not have a regulatory function, so as our drillers say, “It’s all about the science.” It is common for the USGS to partner with other governmental agencies, in this case the City of San Diego, sharing scientific questions, skills, and finances.

WHAT
The next deep monitoring well site in the San Diego area will be drilled to a depth of about 1500 feet, with 4-6 piezometers installed, each to a different depth. Water-level and water-quality information can be obtained from the piezometers. Pressure transducers will be installed to continuously monitor water levels; this real-time data is routed via satellite to a public website. The well site is designed to be a long-term investment for the next 50-100 years. Initially, it will provide information about the local geology and hydrology; later, it can be used to manage groundwater operations.

WHERE
The well location is at the intersection of Home and Federal streets, just off SR94, just west of Interstate 805. Can’t miss us. Look for the big yellow drill rig with USGS on it. You are welcome to stop by anytime. The well site was chosen to be on the west side of the La Nacion fault, paired with the recently completed Chollas Park well site (SDCP), and about halfway in between the El Toyon (SDEP) and Aquaculture (SDAQ) well sites.

WHEN
The drilling operations will begin on Oct 20, 2011, and will continue for about a month. The first 2+ weeks will involve drilling and coring. The 3rd week will focus on geophysical logging, interpretation to design construction of the 4-6 piezometers, and reeming the hole larger to accommodate the piezometers. The 4th week will focus on installing the piezometers. We drill 7 am to 7 pm, everyday, holidays included.

WHY
An additional source of water in the San Diego area may come from the San Diego Formation and the overlying, and possibly underlying, sedimentary deposits of sand, silt, and gravel. Prior to the USGS study, which began in 2001, the location, thickness, and water-yielding character of these deposits was poorly known. Since 2001, the USGS has installed 10 deep monitoring well sites throughout the coastal San Diego area; the sites are a key part of creating a three-dimensional view of the San Diego underground. This geologic, water-level, and water-quality information will help guide public agencies and consultants in how to best utilize the limited, mostly brackish, groundwater resources in the coastal San Diego area.

HOW
We’ll use mud rotary drilling technique, along with wire-line coring to collect undisturbed samples of sediment from selected depths. The piezometers are mostly 2-inch and one 3-inch PVC pipes which are installed to different depths. Each PVC pipe has 20 feet of perforations at the bottom to allow water to enter the pipe only at that depth. Sand is installed around the perforations and a thick clay-like grout is installed elsewhere. The end result is that we will have a nest of 4-6 PVC pipes that we can measure water levels in, and collect water quality samples from. The 3-inch PVC pipe extends to the bottom of the well bore and allows us to conduct a variety of future measurements, such as identifying changes in salinity throughout the entire 1,500 feet section of aquifer.

VISITATION
As usual, you are more than welcome to visit the site; bring your friends, Cub Scout packs, university classes, cameras. Just stop by; we will have an educational outreach area to help us synthesize the information and help communicate it to you. Or call me at the mobile phone below and we’ll set up a time to meet at the site.

MORE INFORMATION
Visit the project website http://ca.water.usgs.gov/sandiego

Wesley R. Danskin
Research Hydrologist
United States Geological Survey (USGS)
California Water Science Center
4165 Spruance Road, Suite 200
San Diego, CA 92101 USA
619-225-6100 office
858-663-6832 mobile

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What’s up with the Chollas Creek wells?

Posted by George J Janczyn on July 27, 2011

Wes Danskin, USGS Project Chief for the San Diego Hydrogeology Project, shares this update from the Chollas Park Monitoring Well installed under contract with the City of San Diego to study groundwater in that area of the San Diego Formation aquifer (for a page collecting all the project updates as well as other groundwater news click this link).

WHAT WE FINALLY INSTALLED
Depth of well screen (SC) and sand are listed

Well #6: SC: 29.5′-49.5′; Sand: 16′-56′
Well #5: SC: 140′-160′; Sand: 180′-119.5′
Well #4: SC: 330′-350′; Sand: 310′-372′
Well #3: SC: 520′-540′; Sand: 432′-585′
Well #2: SC: 760′-780′; Sand: 739′-814′
Well #1: SC: 1040′-1060′, 980′-1000′, & 920′-940′ w/a 40′ sump; Sand: 887′-1100′

DEVELOPING THE WELL
The 6 piezometers at the site were developed, meaning the drilling fluid was removed. The process involves pumping air down each piezometer, which bubbles the water mixed with drilling fluid up and out. The aquifer then refills the piezometer with water, and the process continues until water-quality parameters (conductance, pH, and turbidity) stabilize, indicating that we are extracting only native water from the aquifer. The small amount of water in #5 means that it was not well developed. The low yield of #1 means that it took quite a while and some artful use of air, hose, and patience to get it developed. After winter rains next year, we will go back and see if we can develop and sample #5.

SAMPLING THE WELL
All piezometers have been sampled, except #5 which is dry, and #1, which is taking longer because of the low yield of the fractured bedrock. Sampling of #1 will be completed later this week. A broad range of water-quality constituents will be sampled including major and minor ions, trace elements, stable isotopes of hydrogen and oxygen and radioactive isotopes of hydrogen (tritium) and carbon (C-14), and volatile organics. By analyzing these data we can infer the source of the original recharge, when the recharge occurred, and whether human actions have affected the water. Because the general chemistry of water in the San Diego area like most basins is fairly similar, dependent on the rocks and derived sediment that the water is flowing through, we find it helpful to analyze trace elements and other minor constituents of water to determine of groundwater flow paths. It is rare for water districts or individuals to test for these constituents because they are commonly not viewed as a health or water-treatment hazard. Note, the radioactive isotopes are used for dating the time since recharge and are many, many times below a health hazard.

We also sampled a shallow well downslope from SDCP in order to compare our shallow piezometer data with it.

WATER TABLE
Water table appears to be at about 240 feet; Piezometers #5, #6 are both perched water tables.

PHOTO
Thought you might like to see samples of the water from each of the 5 piezometers we developed. You can tell #6 needs some more development; its a bit cloudy.

But we got great water out of #1, yeah! Getting water out of that fractured bedrock had me a bit worried for awhile.

–wes

 

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A brief talk about the USGS San Diego Hydrogeology Project

Posted by George J Janczyn on July 12, 2011

A few weeks ago I visited the site of the USGS monitoring well being drilled at Chollas Park. The well is part of the USGS San Diego Hydrogeology Project studying water quality, quantity, and flow characteristics in the San Diego Formation aquifer (click here for the story from the visit).

Here’s Project Chief Wes Danskin discussing the program with San Diego KGTV Channel 10 reporter Joe Little (apologies for the less-than-perfect camera work):

 

Also, here’s Joe Little’s report on 10 News.

 

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Legal setback for Sweetwater Authority groundwater desalination project

Posted by George J Janczyn on July 9, 2011

The Sweetwater Authority’s plan to construct five additional wells south of the Sweetwater River in the San Diego Formation as part of its project to expand the Richard A. Reynolds Desalination Facility has hit a legal roadblock. In a ruling on the City of San Diego’s lawsuit challenging certification of Sweetwater’s Final Environmental Impact Report (FEIR), Judge Ronald S. Prager agreed with some of the objections raised by San Diego.

According to the court’s Minute Order, four issues were subject to review: 1) whether Sweetwater complied with the California Environmental Quality Act (CEQA) in approving the project and certifying the FEIR, 2) whether the FEIR contained an adequate project description re. brine discharge point, 3) cumulative impacts, and 4) whether the FEIR includes a reasonable range of project alternatives or discusses feasible mitigation measures.

On issues 1 and 2 the judge denied San Diego’s contentions, ruling in favor of Sweetwater.

On issues 3 and 4 the judge agreed with San Diego that Sweetwater did not take into consideration the cumulative impacts of any particular past, present, or probable future projects, and that the proposed mitigation and monitoring are inadequate.

While the judgment has not yet been made official, it will be based on the minute order, according to Glenn Spitzer, one of the attorneys working on the case for the San Diego City Attorney (click here for a copy of the June 28, 2011 Minute Order).

The foregoing represented Phase I of what is called a “bifurcated” trial. In addition to the CEQA issues, San Diego had also challenged Sweetwater’s water rights in the San Diego Formation. The water rights question will be addressed in a Phase II portion of the trial. A resolution on the water rights issue could take a couple of years, according to Mr. Spitzer.

I wasn’t able to get comments from San Diego or Sweetwater officials, but the issue is on the closed agenda for next Wednesday’s July 13, 2011 Sweetwater Authority Board Meeting.

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A sweet water resource but there’s some salt in the mix

Posted by George J Janczyn on July 8, 2011

On average, San Diego County imports a sobering 80% of its water supply from hundreds of miles away in Northern California and the Colorado River. That figure varies though, depending on which of the 24 member agencies of the San Diego County Water Authority you’re looking at.

Take the Sweetwater Authority. If you look at a map of the Sweetwater service area sandwiched as it is between the City of San Diego on the north and the Otay Water District to the south, you might be surprised it can make do with only 41% imports. What’s the secret?

Sweetwater’s service area includes the western and central portions of the City of Chula Vista, all of the City of National City, and unincorporated areas of the County of San Diego (Bonita). But in a long sliver from the northeast flows the namesake river that’s responsible for much of the liquid wealth.

Illustration courtesy of Sweetwater Authority

For starters, Sweetwater Authority commands the surface runoff from the 230 square mile Sweetwater River watershed, beginning at Green Valley Falls in Cuyamaca Rancho State Park, about a 50-mile drive from Chula Vista. The entire watershed is fully appropriated to the Sweetwater Authority. Sweetwater also owns and operates two reservoirs in the watershed, Loveland Reservoir, and Sweetwater Reservoir, which together have capacity for over 53,000 acre feet.

 

Next, the Sweetwater Authority sits above productive groundwater aquifers. Its National City wells on the Sweetwater River Basin Alluvial Aquifer can supply up to 2 million gallons per day (gpd) of potable water, and additional wells drawing brackish water from the adjacent San Diego Formation aquifer are treated in a desalination facility with a capacity of 4 million gallons per day (gpd).

Looking to increase local storage capacity, Sweetwater Authority and the City of San Diego are cooperating on a proposed four reservoir intertie that could effectively allow them to share an additional 100,000 acre feet of storage without increasing reservoir size, through shared “load balancing” (my term). Some of the extra water could come from local runoff that individual reservoirs might otherwise be forced to spill during peak rainfall conditions.

As for future water requirements in the service area, the Sweetwater Authority’s 2010 Urban Water Management Plan looks forward to relative stability:

“Due to widespread conservation efforts, demands within Sweetwater’s service area have decreased over the past 25 years. Several changes in demographics are anticipated to increase water use in the future…This transition from undeveloped and formerly commercial to residential properties is anticipated to result in an increase in overall water demands within the service area. However, as new buildings replace existing buildings, water efficiency standards for toilets, showerheads, faucets, and urinals, as well as associated changes in outdoor irrigation practices to more “California friendly” landscapes, will cause the per capita water usage to decrease.”

Reverse-osmosis trains inside the facility.

There’s one uncertainty, though: a planned expansion of the Richard Reynolds Groundwater Desalination Facility.
“The Desalination Facility commenced operation in January 2000. The facility was designed to extract groundwater from four alluvial wells and five deep San Diego Formation wells, located on the north side of the Sweetwater River. A sixth San Diego Formation well was constructed in 2006. The Desalination Facility treats brackish groundwater using reverse osmosis (R/O) technology. The Desalination Facility was initially designed to produce 4.0 MGD of drinking water; however, it was constructed with space to accommodate an expansion to produce up to 8 MGD.” (2010 Sweetwater Urban Water Management Plan)

Empty pods in center would allow three more reverse-osmosis trains for a total of six.

One brackish water wellhead is just outside the door to the desalination facility.

 

As planned, Sweetwater’s Board did develop a plan to drill five additional San Diego Formation wells and increase capacity in the desalination facility. It certified a final Environmental Impact Report and approval for the well project last year, Feb 24, 2010.

An obstacle

The City of San Diego promptly filed a lawsuit March 26, 2010, challenging Sweetwater’s certification of the Environmental Impact Report (EIR) and approval of the project. San Diego complained that its concerns about groundwater depletion/overdraft in the San Diego Formation, saltwater intrusion, land subsidence, brine discharge, and other issues were rejected or ignored by Sweetwater.

Meanwhile it was discovered that Sweetwater’s Findings and Facts in Support of Findings had not been included on the CD distributing the EIR. The oversight meant the Board would need to again adopt the Findings and Facts and reapprove the project. This was done at the Oct 27, 2010 Board meeting.

Following this turn of events, San Diego filed a second lawsuit in order to challenge the reapproved project, Dec 9, 2010.

San Diego’s second lawsuit went further than just challenging the new EIR certification and project reapproval. It also asserted that San Diego holds Pueblo water rights to all water within the boundaries of the Pueblo, that the San Diego Formation aquifer underlies parts of the Pueblo, and that the proposed wells would tap the San Diego Formation. The City therefore asked the court for “a declaration regarding its rights to the San Diego Formation vis-a-vis Sweetwater.”

Because of overlap between the two lawsuits, the Court decided to consolidate the two cases on Dec 21, 2010.

San Diego probably feels it has no choice but to press a challenge. Presently San Diego imports 85-90% of its water. According to its Long Range Water Resources Plan (LRWRP) 2002-2030, “By 2030, the City’s reliance on imported water could be as low as 57% if most of the alternative resources options available to the City were implemented.” San Diego is investigating a number of groundwater possibilities. However, as the City’s LRWRP notes, the San Diego Formation “does not appear to recharge naturally at a useful rate.” It also observes “there could also be potential interjurisdictional and water rights issues regarding the City’s use of the basins because they extend beyond the boundaries of the City’s overlaying land.” The City’s lawsuit certainly speaks to that point.

For now, things have been quiet. At Superior Court the only thing pending is a Status Conference scheduled for Aug 12, 2011 in Dept 71, Richard S. Prager presiding.

[late word: although it wasn’t in the court record when I reviewed it last week, I just heard that there was a preliminary decision in June…that the judge agreed that there are several problems with the EIR. If correct, this could mean back to the drawing board for Sweetwater. I’ll post an update tomorrow.]

References

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Otay Water District aiming for new local water sources

Posted by George J Janczyn on June 28, 2011

As the threat of water shortages recedes in the public mind (for the time being), the fact remains that the San Diego County Water Authority (SDCWA, or the Water Authority) has to import roughly 80% of the county’s water requirements. As worrisome as such heavy dependence on the outside is, what makes water planners and managers even more uneasy is that the cost of imported water is rising with no end in sight and the availability of outside water is increasingly threatened by environmental and regulatory circumstances. Reducing dependence on imports is therefore a growing priority.

That’s definitely true in the case of Chula Vista, where the Otay Water District (OWD, or Otay) currently must meet all its potable demand with imported treated water from SDCWA. Actually, OWD’s service area isn’t just Chula Vista, it includes parts of southern El Cajon and La Mesa, Rancho San Diego, Jamul, Spring Valley, Bonita, eastern City of Chula Vista, East Lake, Otay Ranch and Otay Mesa areas.

In 2005 OWD delivered about 40,000 acre-feet (by comparison, the City of San Diego delivered about 199,000 acre-feet) although effective conservation measures over the past two years have reduced those numbers.

OWD has virtually no local water resources of its own. Some people might point to the Lower and Upper Otay reservoirs in Chula Vista but those belong to the City of San Diego.

Following the great 1987-92 drought, OWD in 1994 established a goal of being able to meet 40% of annual demand from local water sources if water becomes unavailable from the Water Authority. It signed agreements with the Helix Water District and the City of San Diego for access to treated water from those systems. It aggressively moved to promote recycled water use and required dual piping for new developments (one set for potable, one for recycled irrigation). Otay now maintains the largest recycled water distribution system in the county. It supplies the recycled system from its Ralph W. Chapman Water Recycling Facility and from San Diego’s South Bay Water Reclamation Plant.

The District is now directing a groundwater well project within the master-planned Rancho Del Rey community located a few miles east of I-805 and north of H Street.

It turns out that in 1991 when the McMillin Development Company was building in the neighborhood, it drilled a 7-inch well to 865 feet to produce water for dust control and soil compaction. After construction the company had no further need for the well and put it up for sale.

OWD purchased the land and well in 1997 and explored its potential as a potable water source. It appeared that a reasonable amount could be produced, but the water was salty and of poor quality, requiring reverse-osmosis desalination. After reviewing design and construction cost estimates in 2002, the District decided it could not justify the expense at that time so it suspended the project and waited.

By 2010, the cost of imported water had been rising dramatically and price increases projected to continue. Looking again at the well project, estimates came in at about $1500 per acre-foot. This time Otay decided it would be economically viable and the Rancho Del Rey Well Project was underway.

In September 2010 a new 12-inch well was drilled to 900 feet and testing revealed the well had the potential to produce 500 acre-feet of water per year (AFY).

A few weeks ago on June 16, 2011 the District held an open house to explain the project and show architectural renderings to neighborhood residents and other interested individuals.

The reverse-osmosis treatment facility design will feature architecture and materials to mirror the appearance and character of the residential and institutional structures in the vicinity of the site. The well site is adjacent to a large child daycare facility and the relatively new neighborhood is comprised of mostly single family residences. There are spacious parks, schools, and other public facilities nearby.

Proposed design for the water treatment facility

New connections to a District water main will include an inlet for blending well water with potable water and an outlet for distribution of the blended water into the system. Brine generated in the treatment process will be discharged into the City of San Diego’s sewer system in compliance with requirements of the National Pollutant Discharge System (NPDES), San Diego Wastewater Department, and the County Department of Environmental Health.

The environmental impacts and a detailed project description were published in a Mitigated Negative Declaration following CEQA guidelines.

Otay estimates that operations of the 500 AFY well could begin by April 2013.

Otay is also looking into the feasibility of purchasing desalinated seawater from a proposed reverse osmosis plant that is planned by a private developer for Rosarito Beach, Mexico.

The County Water Authority is also conducting a feasibility study of obtaining desalinated water from that facility, but Otay is evaluating conveyance and treatment options for itself and negotiating separately with the parties in order to produce a Principles of Understanding document for establishing water supply resource acquisition terms.

For additional information about the above projects and much more, please see Otay’s 2010 Urban Water Management Plan.

 

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Chollas Park groundwater study: pictures tell the story

Posted by George J Janczyn on June 21, 2011

Here’s the latest from Wes Danskin’s log on the USGS groundwater study at San Diego Chollas Park (previous log entries on this study are here).

WHAT’S NEW
Done drilling, chose depths for wells (piezometers–pressure sensing wells), installed 2-inch PVC piezometers, and are developing of them as I write this. Decided to include photos of each activity so you don’t have to read all this, just view the photos.

CORING TELLS THE STORY
Hit bedrock (Santiago Peak volcanics at 877 feet). Core at 895 feet is shown below. Many fractures are present

PICKING THE DEPTHS OF PIEZOMETERS
Based on geophysical logs, drill cuttings, cores, pore water chemistry, geologic mapping, evolving concepts of groundwater flow, likely constraints to developing a water supply, defining the yuck factor of Chollas water, taking advantage of evaporating Chollas Lake water … one of the more difficult things I do. You definitely get your money’s worth from the Chief Scientist on the project (me).

Well #1: 1040′-1060′, 980′-1000′, & 920′-940′
Well #2: 760′-780′
Well #3: 520′-540′
Well #4: 330′-350′
Well #5: 140′-160′
Well #6: 30′-50′

DEVELOPING WELLS
Send air down the wells to force water and left-over drilling fluid up and out. In the photo you’ll see water being ejected from one of the wells.

As we extract water/drilling fluid, the aquifer replenishes the well water, which eventually ends up cleaning the well of our drilling effects. We monitor clarity of the water, pH, conductance, and temperature to known when we have removed drilling-related water and fluids and when we have native ground water. Great news is that the fractured well shown in the photo above makes water, not much, but makes water via those fractures.

NEXT STEPS
Sampling the wells for water quality.
Installing a vault to protect the wells.
Installing water-level monitoring equipment, and satellite link.
Putting the information on our website.

Whew, I’m exhausted; almost done.

–wes

 

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Site visit: USGS groundwater study at San Diego Chollas Park

Posted by George J Janczyn on June 7, 2011

Recently Wes Danskin, Project Chief for the U.S. Geological Survey (USGS) San Diego Hydrogeology Project, shared notes from his log (here and here) regarding installation of a monitoring well at Chollas Park that will be used as part of a study to learn about water quality, quantity, and flow characteristics in the San Diego Formation aquifer. Funding for the well comes from the City of San Diego.

Last Thursday I received an email from Danskin: “Stop by if you’d like, we’ll be on site for about another week completing the piezometer installation.” No need for a second invitation; the next morning I grabbed my camera and headed over to the project site.

The well is just west of Chollas Lake which itself is just west of the College Grove shopping center near the SR-94 freeway at College Avenue.

Several other visitors were already there, including a few members of the San Diego Association of Geologists (SDAG). 10News reporter Joe Little was there, preparing to interview Danskin for the evening news.

(all photos can be clicked for enlargement)

10News reporter Joe Little (left) prepares for the interview with Wes Danskin.

Wes animatedly talked about a new three-dimensional geologic map of the region that he’s been working on. No previous geologic studies in the San Diego/Tijuana area have produced such a map. According to the SDAG website (“Mapping the San Diego Underground”):

“A total of 91 wells, which showed stratigraphy older than Quaternary age, helped provide depth information to produce this 3D hydrogeologic framework model. This study relied on pre-existing GIS (geographic information systems) datasets including DEM (digital elevation model), surface geologic maps, drilling and e-logs, and literature references to wells or outcrops. Direct examination of USGS multi-depth wells provided the most reliable “ground truth” for geologic boundaries used in the model.”

Danskin explained there are three types of wells: 1) monitoring wells to identify water levels and quality and geology of the groundwater basin; 2) pilot production wells to determine the quantity of water flowing through the ground; 3) full scale production wells. For the San Diego study, the first two types are being used.

Continuing, Danskin said the San Diego Formation extends north-south from La Jolla to south of the border, and west-east from the ocean to the vicinity of the I-805 freeway. Groundwater has been extracted from the San Diego Formation for over 50 years. Sweetwater Authority has been distributing it to National City and Chula Vista.

“The important part about this well is that we’re actually able to get down into the hard rock,” said Danskin. “None of the other wells, with the exception of one near Qualcomm Stadium, were we able to identify this important part of the geologic story,” he said, noting that “the critical part of what we’re doing is defining how the geologic layers are arranged and that allows us to understand how the water moves through them.”

An interesting fact: using carbon dating they found that it could be up to 30,000 years since that groundwater was last in the atmosphere.

Little asked whether pumping and treating groundwater can be cost-effective. Danskin replied that Sweetwater Authority’s pumping of groundwater shows it is already cost-effective. It will gradually become even more competitive because the price of imported water continues to increase. It is becoming more attractive from a reliability point of view too, because we import up to 90% of our water from the Colorado River and the Sacramento-San Joaquin Delta, and both of those sources are climatologically, environmentally, and politically at risk.

Danskin said chances are that most of the water in the Formation will be salty and require reverse osmosis treatment…not as salty as the ocean but it may contain the same salt level as V-8 juice. Still he has an optimistic outlook about the project finding a reliable groundwater flow. “It’s taken about ten years,” he said, “but things are finally starting to make sense.”

A typical tricone drill bit.

Numerous soil samples are taken at regular checkpoints as the drill goes deeper.

Danskin discussing the various well locations in San Diego.

 

Here’s video I shot while Danskin discussed the project:

 

See also Joe Little’s report on Channel 10 News:

 

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