Dewatering Site Map for 2016 now posted

Dewatering for basement construction is about to get into full swing for the 2016 “season.”   As of this writing, two sites have completed dewatering, including one that discharged nearly 31 million gallons into the storm drains, one that is about one-half way through the dewatering process, and three more that are imminent.  The City’s Department of Public Works has updated its dewatering site map, which can  be also accessed  from Save Palo Alto’s Groundwater’s Maps Page.        While you are on our Maps page, check out other maps relevant to Palo Alto’s groundwater, including an updated groundwater depth map from Bob Wenzlau (Terradex) that also shows the flood zone and locations of toxic plumes, a map  created by Save Palo Alto’s Groundwater from data provided by Palo Alto’s Public Works Department that shows the locations of the 2015 dewatering sites, and a map from a 1995 USGS report documenting historical subsidence in the Bay Area of between 1.5 and 3 feet in Palo Alto (and much more in San Jose).

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3 Responses to Dewatering Site Map for 2016 now posted

  1. Rita Vrhel says:

    How is it possible for 30.3 million gallons of community groundwater to be extracted from the shallow aquifer during the construction of 1 residential basement? I know this amount is accurate as it was the first dewatering site to be metered by the City of Palo Alto Public works Department. The basement was listed as 3,545 sq feet.

    So little of this water was reused or recycled. In a period of extended drought and dying trees city wide, this waste of groundwater is quite appalling!
    It really can not continue. An estimated 216 million gallon extracted in 2015; how much more groundwater will be wasted before we say ENOUGH!!!

    Let’s work together to either reuse,recycle or re-inject the extracted groundwater or require use of construction techniques that minimize groundwater extraction. It does not need to be an either or situation. Residents can have their basements and the shallow aquifer can retain it’s precious water. It is only a matter of time before we all agree massive dewatering and callous waste of a limited resource can not continue.

    Will we wait until we have not choice? … and no groundwater? I believe we can do better.

  2. Lynn Chiapella says:

    Midtown has suffered enormous loss of ground water due to the many new basements. Sometimes the dewatering can last 6 months. Does the City check the geological maps as to where the undergrounded creeks or small aquifers are located prior to the dewatering project?

    Has anyone seen the city maps or they “lost” in the archives? Has anyone recently tested the “non-potable” water? A citizen captured some of the water and had it tested in the late 90’s after another drought. It was potable. She submitted the results to the City (Joe Teresi as I recall). He said that there was no effect by dewatering and that the water table always returned to “normal”. Jody and I thought that was crazy, but for our sanity in the city of Alice in Wonderland we let the project go.

  3. Esther Nigenda says:

    Thank you for your comments Lynn. As we understand it, the City currently allows basements to be built any where that is not the designated FEMA flood zone. No other maps are used as even historic and/or repeated flooding of a location does not disqualify that location for basement construction in Palo Alto.

    According to the 2016 Dewatering Guidelines,, dewatering at any one location can currently last no more than 10 weeks. However, these are “Guidelines” and Public Works has decided they cannot imposed fees for exceeding this time limit after all.

    Save Palo Alto’s Groundwater has not tested the groundwater. If any one has done so recently, we welcome their results.

    During a drought (little to no recharge from precipitation) the water table may return to near “normal” once the dewatering stops but only because the Santa Clara Valley Water District, to avoid subsidence and salt water intrusion, recharges the aquifer with imported water (paid for with taxpayer money). In any case, for several hundred feet around the dewatering site, the water table is lowered by several feet for the duration of the dewatering and nearby properties may suffer some damage (cracked windows, walls, slabs or foundations, doors that won’t open). This damage depends on a variety of factors including proximity to dewatering site, types of soil, location (underground creeks, alluvial fans, etc.), amount of water pumped, duration, drought conditions, etc.

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