Basement groundwater pumping raises concerns

Experts question safety of massive groundwater pumping for basements in Palo Alto

Day-in, day-out from April through October, residents of Old Palo Alto have noticed the incessant pumping of water -- estimated at up to 13 million gallons taken from one property alone.

In the last two years, eight property owners have built basements in or near the pricey neighborhood, according to Mike Nafziger, a Public Works Department senior engineer.

The catch is that the high water table in the area forces "dewatering" of millions of gallons of groundwater before a basement can be built. Yet because the aquifers flowing under Palo Alto are billions of gallons the impact of pumping is relatively small, according to one city official. At most it would cause a temporary depression in the water table, he said.

Noise annoyance aside, some residents are concerned about what's in the groundwater and whether pumping it out actually draws a toxic plume from the Stanford Research Park closer to their residential neighborhood.

The plume, which mainly stems from an underground tank that for years leaked trichloroethylene (TCE) as well as other chemicals, was first discovered in 1981 and was listed as a Superfund site in 1990. The most prevalent chemical, TCE, is a known carcinogen and solvent for cleaning metal equipment. It is already the subject of ongoing study and clean-up effort.

There are regulatory safeguards at various levels of government. But testing of pumped groundwater is optional and sporadic, and the multiple agencies involved create a potential for gaps.

City officials don't appear to be worried.

The pumping is legal and approved by the city's Public Works Department and Palo Alto's Regional Water Quality Control Plant in the baylands.

But sucking water out of shallow wells to "dewater" a site so a basement excavation can occur ranges from 30 to 50 gallons per minute, 24 hours a day for between three and six months, according to a 2008 city staff report.

The volume of water removed ranges from 3.9 million to nearly 13 million gallons per property. The eight permits over the past two years totaled just under 50 million gallons, according to city estimates equivalent to approximately 75 Olympic-size swimming pools.

The latest pumping involves Google co-founder Larry Page's large basement project in the 2100 block of Bryant Street.

In 2008, some residents questioned whether pumping from earlier projects in the area might be drawing the toxic-contaminated plume toward residential neighborhoods. The plume presently predominantly underlies non-residential areas in the vicinity of Page Mill Road and El Camino Real -- but it includes the Chesnut-Wilton-Ventura neighborhood of smaller homes as well as aparetments along Sherman Avenue near the North County Courthouse, according to a Santa Clara Valley Water District map.

The Larry Page property is about 1,500 feet east of the contaminated plume, according to the map.

Five of the eight residences where the pumping is happening are aligned north and east of Page's property, lying between Oregon Expressway and Embarcadero Road.

So far, no toxics have been found in water pumped from the projects, according to Ken Torke, environmental control programs manager at the city's Regional Water Quality Control Plant.

But that's because no one has looked. The treatment plant has not require a single property to test the water, Torke said.

The homeowners are not required under city, state or federal law to have the pumped groundwater tested. But the boundaries of the contaminated plume have not been precisely measured and need further study, according to a review of the Superfund site this year by the San Francisco Bay Regional Water Quality Control Board, a state agency.

Stephen Hill, who heads the toxics-cleanup division at the water board, said there are two ways his agency interacts with cities: "We copy the city on all correspondence about HP 640 and other cleanup sites as a matter of courtesy." He said the agency also is available to provide expertise to help cities investigate vapor-intrusion concerns.

Yet some hydrologists express concern that large-scale pumping could accelerate the spread of the contaminated plume.

Yoram Rubin, a civil and environmental engineering professor at the University of California, Berkeley, who specializes in hydrology, said there could be reason for concern. The pumping and direction of flow of the aquifer "could have the combined and significant effect of accelerating the migration of contaminants further into the residential areas.

"It could be a significant risk and deserves careful study," he said.

But the volume of residential pumping pales in comparison to longstanding pumping done to clean up the contaminated water.

"Multiple pumps in the center of these (Superfund clean-up) sites are pulling in an equal or greater amount of water every day. A small project, a half a mile away, is unlikely to change anything," Torke said.

The regional water board's 2010 review of the HP Superfund site recommended additional monitoring of the plume in order to ensure containment. (See Weekly story, Oct. 8, 2010).

"With such uncertainty, I would worry about the effects of this pumping," Rubin said, speaking as a hydrologist but not as a specialist in Palo Alto groundwater.

Others have argued against the continued basement pumping because knowledge of the exact nature and extent of the toxic plume has been shaky for some years.

"Many containment plumes are mapped, but others are poorly characterized. Such risks additionally weigh against construction dewatering," Palo Alto resident David Stonestrom wrote in an open letter to the Palo Alto City Council in 2008, when new regulations regarding basements were adopted.

Stonestrom, U.S. Geological Survey hydrologist, said he wrote out of concern as a resident and not in his professional capacity.

But city officials say there is little to be concerned about regarding these short-term pumping projects because of checks and balances relating to the regulatory agencies involved.

Three systems contain the TCE-bearing plume, according to Roger Papler, case manager for the Regional Water Board. The systems are (1) extraction wells on the HP property, (2) wells off the HP property and (3) a high-volume filtration system at the Oregon underpass, which can filter up to 600 gallons of contaminated water per minute.

The measures currently in place "effectively contain the plume," Papler said.

"It would be very difficult for those operations to draw the ... plume into the local groundwater. Even if they did, the chances of the water exceeding maximum contaminant levels for drinking water are pretty low."

But vapors are a concern.

It's uncertain whether vapor from the contaminated plume could diffuse into basements. New technologies to measure such intrusion have not been used at the HP Superfund site, he said.

TCE intrusion was discovered in 2009 in the basement air of the Wilson Sonsini Goodrich & Rosati law firm near the eastern edge in the Research Park. Papler said a work plan is being developed to address the vapor intrusion and monitoring questions.

The city's Department of Public Works and the city's Regional Water Quality Control Plant evaluate construction plans that involve dewatering. They can -- but often don't -- require contractors to test water for contaminants before pumping it into storm drains, according to Phil Bobel, Public Works' acting assistant director for engineering.

"If it's in the vicinity of known contamination plumes, then we require them to do tests for the contaminating substances in question," Bobel said.

In addition, the regional water board and Hewlett-Packard jointly supervise the plume's clean-up and containment.

"Any time we have a groundwater-pumping project, we send it off to them, and whatever they comment on we incorporate into our environmental review process," city Planning Director Curtis Williams said.

The Palo Alto wastewater-treatment operation reserves the right to test water before contractors discharge it into city storm drains, according to Torke. But no testing was required this year, he said.

"They were not near enough to sites of known groundwater contamination," Torke said.

All basement applications must have a soil-type and groundwater report, which he said help determine the volume and duration of pumping.

"The volume of water potentially involved depends on the soil type," Richard Woodard, principal engineer at San Carlos-based Romig Engineering, said. Romig has done a number of the "geotechnical" reports in Palo Alto that relate to pumping.

"If it's clay, water will come but at a reasonable rate. If the soil is more permeable, the dewatering will continue throughout the project," he said. While no testing was required for Page's basement project, it is less than 1,500 feet from the plume edge, as estimated by the regional water board's 2010 report. Torke said previous nearby testing had shown no contamination.

Groundwater pumping is unlikely to pull the contamination beyond its existing known boundaries, Torke said.

"When you think of millions of gallons of water, it seems like an Olympic swimming pool, but the plume itself is probably on the order of billions of gallons of water," he said.

Furthermore, the city officials said that pumping, which moves groundwater, doesn't necessarily move contaminants at the same rate.

Chlorinated solvents such as TCE "are heavier than the groundwater that they've seeped into, so they tend to sit at the impermeable bottom of the shallow aquifer," Torke said.

"These plumes tend to move more slowly than the water above."

In 2008, Torke said he grabbed three water samples at a Waverley Street site near Page's property "out of curiosity, wondering if the plume had moved and nobody knew about it. There wasn't any contamination in it," he said.

The city has encountered contaminated groundwater near other plumes, as it did in 2008 under the then-planned Taube Koret Campus for Jewish Life on the former Ford Aerospace site in south Palo Alto. That discovery resulted in significant changes in design, including requiring all buildings to be raised a full story off the ground for air circulation.

When contaminated water is found, such as in the Taube Koret case, it can't be discharged into city storm drains. The removed water is instead routed to the sewage-treatment plant, according to Torke.

At the treatment plant, a three-step process lets chemicals settle, exposes the water to bacteria -- which "essentially chomp away at large organic compounds to make smaller ones" -- and filters it, Bobel said.

If water contamination exceeds sewage-treatment-plant limits, it needs to be brought to a hazardous-waste site in barrels or tank trucks, Bobel said.

Some city officials suggest that older construction styles might have greater consequences for groundwater flow than the new short-term projects.

The city used to allow permanent groundwater pumping out of basements prior to 2006, which an official said could have a greater overall impact on the movement of contaminated-plume water. While there is currently no "mandatory phase-out" of existing permanent drainage systems, the city considers such installations worrisome.

However, city officials said that public health concerns associated with standing water, not concerns about the potential movement of groundwater, motivated the city's decision to outlaw new permanent drainage constructions. The city now only allows groundwater pumping during construction and only during the dry season, between April 1 and Nov. 1, so as not to overload the city's storm-drain system.

Prior to 2006, the draining method was a combination of perforated drain pipe flowing into a sub-basement catch basin and being pumped to the surface via garden-hose-size pipe. The water is not tested.

Both permanent pumping systems, such as the catch basin, and one-time pumping during construction address a central problem of building in areas with high water tables: the pressure groundwater exerts on basements, causing poorly constructed basements to try to float upward.

"The new regulations mean that the waterproofing materials must be installed in such a way as to withstand the extra hydrostatic pressure," said Brig Ord, a local contractor who has installed basements before and after the change in regulation.

Ord estimates that the ban on permanent pumping systems has increased the cost of building a basement in a high-water zone by about $20,000.

Older basements currently escape city oversight. When originally installed, the projects didn't require city approval, and so the city doesn't have a complete record.

"When we discover a permanent-pump system, we try to discourage the owner," Bobel said, adding that many still exist undetected.

"The short-term pumping associated with the construction regulation is less concerning than those long-term projects that do influence the water table," Bobel said.

Related stories:

Citizens voice concern over extracted groundwater

What is community worth to you?
Support local journalism.


Like this comment
Posted by FormerPAresident
a resident of Fairmeadow
on Nov 19, 2010 at 7:51 pm

The City should require testing of any water discharged to the storm drain system. Why would they not?

Like this comment
Posted by Jody
a resident of Old Palo Alto
on Nov 20, 2010 at 3:35 am

The California Regional Water Quality Board (Toxics Division) released their five year report on 9/30/2010. Here is the link to the full report.
Web Link

Like this comment
Posted by anonymous
a resident of Another Palo Alto neighborhood
on Nov 20, 2010 at 8:54 am

I'd almost respect those of you with the courage to admit, "I'm jealous that other people can have things I don't have, like full basements." I don't know how many people would agree with you, but at least we'd know where you stand.

What no one respects is the fake outrage. "I'm shocked, just shocked at the horrible waste of water." @FormerPAresident do you also want to test everyone’s irrigation and car wash runoff water? 10 gallons per week of runoff per household is over 10 million gallons per year Citywide. Why would you not?

Like this comment
Posted by Janny
a resident of Charleston Gardens
on Nov 20, 2010 at 11:39 am

After the Loma Prieta earthquake my house felt like it was a ship on an ocean. You could feel the water swishing back and forth under my house for many hours, and water came up through cracks in the concrete due to liquefaction. I live in south Palo Alto; there are many such plumes of water under the entire city.

All the people who keep wanting to put HSR in a tunnel or trench don't realize how impossible that is with so many plumes of water moving from the hills to the Bay under our City.

Rather than pay huge water bills it may pay you to dig a well!!

Like this comment
Posted by Sarah
a resident of South of Midtown
on Nov 21, 2010 at 10:55 pm

Thank you for finally covering this important topic.

Like this comment
Posted by Does not add up....
a resident of Community Center
on Nov 22, 2010 at 7:55 am

I thought there were recent rules passed to have permeable driveways and not have too much concrete - since that reduces rain-water reaching the water table.

How come we don't care when we suck all this water out and send it to the bay.


Like this comment
Posted by Not a good idea
a resident of Another Palo Alto neighborhood
on Nov 22, 2010 at 9:06 am

Palo Alto is built over marshland at the edge of the Bay. With plumes of water flowing underground from the hills to the bay; if you pump out water to build a full basement, more water will continue to flow from high to low so that water will be quickly replaced.

I suppose they plan to build very expensive waterproof basements - good luck!! Forget about the full basement, make it a crawl space for your electrical wiring, water pipes and sewage.

Like this comment
Posted by Peter K. Mueller
a resident of Barron Park
on Nov 22, 2010 at 11:15 am

Yeah, in accordance with some of the other commentators, it would be great to consider ways to use the problem ground water to supplement our limited water resources. May be the writers of the forgoing comprehensive and clearly presented article could compose another one addressing the factors involved in use.

Like this comment
Posted by Steve
a resident of Old Palo Alto
on Nov 22, 2010 at 11:33 am

The City of Palo Alto Construction Dewatering System Policy states, “Dewatering is only allowed from April through October.”

Web Link

Yet today, November 22, 2010, high volume dewatering continues at 2021 Webster Street in clear violation of City policy.

Video at Web Link

When will the City stop this waste?

Like this comment
Posted by SuperD
a resident of Community Center
on Nov 22, 2010 at 11:40 am

Why does the city continue to allow new home builders to put in basements? I understand that home builders want to extra space, but water tables raise and fall over time. Odds are pretty good that water will seep in at some point in time and you'll have a very expensive swimming pool!

Like this comment
Posted by ChrisC
a resident of College Terrace
on Nov 22, 2010 at 1:09 pm

Wow !! I had no idea this sort of thing was going on. Thanks, Steve, for the video. I've seen such piping of water from time-to-time and thought .. what a waste. We desperately need new ways of collecting water. Could this water not be used for landscaping? Could there not be some way to contain the water for later usage? I think Californians need to look at cisterns to catch rainfall as well. Water concerns will be one of Rich Gordon's interests in the Assembly.

Like this comment
Posted by Frank
a resident of Ventura
on Nov 22, 2010 at 1:18 pm

>We desperately need new ways of collecting water. Could this water not be used for landscaping?

The issue is economic - fresh water is way too cheap to make collecting this and trucking it somewhere cost effective.

There was some construction like this near my parents house and several large trees died. Some came back the next year and some had to be removed.

If the ground water is that high your basement will be wet eventually. You can seal it for a while but eventually the water will win.

Like this comment
Posted by An Engineer
a resident of Downtown North
on Nov 22, 2010 at 2:04 pm

Pumping out the water table is a great way to tweak the neighbors. The resulting local ground subsidence will crack their foundations to pieces.

Like this comment
Posted by Bryant St neighbor
a resident of Old Palo Alto
on Nov 22, 2010 at 8:45 pm

In fact, subsidence has occurred in this neighborhood. A far more serious issue actually.

Like this comment
Posted by Another Engineer
a resident of Midtown
on Nov 23, 2010 at 5:16 am

I live in Midtown on the other side of Oregon Expressway near Old Palo Alto. We also have had many homes construct basements. These construction sites excavate right up to the property line and drill powerful wellpoints along the perimeter of the properties. I have seen many homes dewater at a high rate for longer than six months. I have seen trees die years later. A neighbor of mine felt that his home began leaning towards one of these newer homes a few years later. My feeling is that this is happening due to the compressibility of our clay soils. When the water table is intentionally lowered with wellpoints during construction, this creates a situation of desiccation of the clay soils, which can cause damage to homes in the area since dewatering causes loss of buoyancy support in the soil.

On the other side (In Old Palo Alto), there was a home which was discharging 100,000/day at a time when we were in our third or fourth year of drought. This home had a sign outside proclaiming it to be "Green". I felt that this was a bit hypocritical when our state was in severe drought, where I had let my yard die back, and asked my family to cut their water use.

I feel that something must be done about this. Basements should not be allowed to be built in areas which require the property to be dewatered. Most homes in the Bay Area do not have basements for a good reason. I feel sorry for people who have been duped into this. The basement walls will eventually fail from the hydrostatic pressure. Additionally, I would not want to live near a home with a basement.

Like this comment
Posted by Jenny
a resident of Charleston Gardens
on Nov 23, 2010 at 7:08 am

The water table under my house is only 4 feet down. A neighbor built a house with a sunken master bedroom. The bedroom and bathroom get flooded every rainy season.

The homeowners filed a law suite against the contractor who built the house for not informing them that the water table was so high, I don't know who won the law suite. However, another neighbor had to drill down to find out where the water table was before they were allowed to build.

Like this comment
Posted by palo alto mom
a resident of Duveneck/St. Francis
on Nov 23, 2010 at 8:30 am

Using common sense, if you need to pump for months to keep a hole in the ground dry, perhaps there should not be a hole in the ground?

Like this comment
Posted by Charlie
a resident of another community
on Nov 23, 2010 at 8:51 am

Who said: "DO NO EVIL"!!!

Like this comment
Posted by Stan
a resident of Midtown
on Nov 23, 2010 at 2:35 pm

I guess somebody should tell the city and PAMF to evacuate their buildings (underground garages)

Like this comment
Posted by william
a resident of Old Palo Alto
on Dec 1, 2010 at 7:52 pm

What about all the homes that have pumped out groundwater that are near this contaminated plume?

Looking at the link of the map, there have been many homes which have pumped out groundwater all around this contaminated plume. I have seen groundwater pumping in College Terrace, and both sides of Oregon close to contaminated areas. Not sure about Barron Park.

Looking at the map, the plume has crossed Alma into neighborhoods, and is under many residential areas. Is it safe to eat fruit on trees in these areas?

This excavation and groundwater pumping have been going on for MANY years, but seems to be increasing.
I have seen them dig right up to the property line to put in these basements on really small lots. One person was afraid his rental home and kids would fall into the pit since only an old chain link fence was between his home and the hole.

Who is monitoring these excavations and making sure these toxic substances have not been pulled under our homes?

Like this comment
Posted by Michael
a resident of Old Palo Alto
on Dec 1, 2010 at 10:22 pm

In many cases, contractors excavate right up to the property line and then come back to adjust the setbacks, making it look as if they are obeying the setback laws. Many excavations fail to shore up excavation sites. Here is an example of an excavation outline where you can clearly see the area for the small cut for the ingress on the property line.

Web Link

This construction site pumped out groundwater for more than 6 months at an extremely high rate, about 70,000 gallons of water everyday. This was done during our 2007 drought. I cannot understand the logic of this. While my neighbors and I were sparingly watering our yards, this builder "vacuumed" out massive amounts of water from this site and dumped it into a storm drain. Ridiculous! Furthermore, the builder and the city never responded to complaints of subsidence and damage to adjacent structures. Incredible!

Like this comment
Posted by william
a resident of Old Palo Alto
on Dec 4, 2010 at 9:04 am

I have an organic garden with mature fruit trees. My home is pretty close to this chemical mess, and some foolish people did pumped out groundwater to put in a basement on their small lot.

Is there a place where I can send soil and water samples?

If anyone knows, please let me know.

We eat the organic fruits and vegetables that we grow, and give the rest away to friends.

I never realized that this groundwater problem existed!

Like this comment
Posted by Isaac Achler
a resident of Midtown
on Dec 5, 2010 at 2:31 am

We should be concerned about the TREES who's livelihood depends on the groundwater, that is pumped out (for basement construction). Drying up the water underneath their roots will destroy the trees in neighborhoods located far away from the basement's property !!!
Furthermore, why waste the millions of gallons of pumped water into the drainage, instead of using it for future irrigation of trees and lawns (and save the precious Hetch Hetchy water).

Like this comment
Posted by Old Palo Alto Resident
a resident of Old Palo Alto
on Dec 7, 2010 at 3:14 pm

Thanks to the Weekly for doing such a great article.

The reason the city workers, city council and city planners don't give a fig about this problem is money.

This is big business and big money for Palo Alto.

The City makes a fortune with permits and keeps city workers happily employed. Go to the permit office and see how busy it is with people wanting to tear down/pump basements. I was there one day and this guy comes in and says "I want to tear down this house, can I do it". The city planner says "sure, no problem".

So, they don't care about plumes, basements that mess up neighbor's homes, killing trees, or the quality of our wonderful neighborhood.

I hate to be a "Debbie Downer" but until people that care about this issue get on the planning commission and city council we will continue to see basement pumping.

...the only other hope is getting the EPA involved?

P.S. - the house on 2021 Webster Street is still pumping water today. I thought this was not permitted after October. The other trick it to get "exceptions" to city codes...just pay the city and you can break the codes/rules.

Like this comment
Posted by Chris
a resident of Crescent Park
on Dec 7, 2010 at 8:48 pm

After the 1998 flood in Crescent Park, people built homes with basements that needed to pumped out groundwater. All of the homes pumped out groundwater longer than 6 months. Our neighbors wondered why the city would permit this since the area flooded. Building regulations require homes to be raised above the flood level now, yet people deliberately ... and with the full blessing of our city agencies ... build basements in our acquifers. Where is the sense in that?

What about salt water intrusion into the groundwater which provides water for the mature city trees in our area?

There are two known plumes (contaminated ground water) in Palo Alto: one under and in the area of the JCC and the other in the Research Park. Drawdown wells in those area may accelerate migration of the contaminants into residential areas. Needs serious study before any more groundwater pumping is allowed.

Like this comment
Posted by Steve
a resident of Old Palo Alto
on Aug 6, 2011 at 10:46 am

The madness continues. A contractor began drilling well points for another dewatering operation on 585 N. California Ave today. An extremely large Baker tank is already on the property. They must be expecting significant water volumes. Given the history of a nearby property on Webster, they will indeed draw down a very active shallow aquifer which is supporting several very old and beautiful redwood trees on neighboring properties.


Like this comment
Posted by vladrad
a resident of Palo Verde
on Aug 14, 2012 at 4:44 am

We all should do this! And water problem will be gone. Just build more basements!

Sorry, but further commenting on this topic has been closed.

Don't be the last to know

Get the latest headlines sent straight to your inbox every day.

Vegan cafe to land in Mountain View this week
By Elena Kadvany | 7 comments | 4,052 views

What Would it Take to Get Tech Companies to Move Jobs Out of the Region and Is This a Good Idea?
By Steve Levy | 12 comments | 1,121 views

A Power Play
By Sherry Listgarten | 4 comments | 934 views

College Match
By John Raftrey and Lori McCormick | 0 comments | 865 views

Piles of artwork
By Cheryl Bac | 0 comments | 352 views


Vote now!

It's time once again to cast your vote for the best places to eat, drink, shop and spend time in Palo Alto. Voting is open now through May 27. Watch for the results of our 2019 Best Of contest on Friday, July 19.