First, thank you to the nearly 100 supporters who came to City Hall on March 7th and to all those who wrote letters of support. Not a single person spoke in opposition to our proposals, including three persons from the construction industry, thereby demonstrating strong community support for our position. The Palo Alto City Council unanimously passed a motion to implement enhancements to the 2016 Dewatering Guidelines. These will take effect for the 2017 dewatering season, with an exclusion for those properties that have already received their building permits.
Special thanks to Councilwomen Lydia Kou and Karen Holman who proposed an amendment, which passed, to significantly reduce grandfathering by requiring projects that have preliminary conditions of approval but have not yet received building permits be included in the 2017 enhancements.
Check out Palo Alto Online’s coverage and this terrific video made by 8-year old Cate A. and presented at the March 7th meeting:
There is still work to do for 2018. The current regulations help, but are still far from requiring no discharge of groundwater to the storm drains while avoiding increases in flood risks. Read more for the details of Council actions and our comments.
Generally speaking, the 2017 Enhancements simply correct significant flaws in the 2016 Pilot Program, while also enacting changes to the City’s Ordinance to provide the City the legal authority to enforce these regulations.
- For 2017, dewatering applicants are required to provide actual measurements for each specific site verifying the pumping rate and water table pull down predicted in the “Enhanced” Geotechnical Report.
Note: The three “Enhanced” Geotechnical Reports prepared in 2016 were in error by up to a factor of 10, and none of the reports was even close to the measured results.
- Pull down of the groundwater table under the basement slab is to be continuously monitored and be no more than 3 feet below the bottom of the slab at any time, and raised to 1 foot below the bottom of the slab when the slab is poured.
We expect this to modestly reduce pumping more groundwater than is needed.
- Additional fees are required to provide the City funds to monitor basement dewatering.
We expect this requirement will, at a minimum, provide more accurate and complete data.
- Modest, but still meaningful incentives are provided for those who maintain pumping at 30 gallons per minute (gpm) or less throughout the project.
This is still a lot of water – approximately 3.6 million gallons over a 12-week pumping period (but could be more as the maximum pumping period can be up to 6 months if the pumping rate is maintained below 30 gallons/minute). However, the slower pumping rate would be expected to reduce the amount the water table is lowered and thus, have less impact on nearby properties. For reference, some projects in 2016 pumped over 200 gallons/minute and over 30 million gallons.
- Staff is directed to evaluate and propose additional regulations to take effect in 2018.
Based on the results of the 2017 dewatering season, our goal is that Staff will propose regulations that simply prohibit discharge of groundwater to the storm drains, along with any other requirements needed to avoid unintended consequences.
In our opinion, and as a separate but relevant issue, the impacts of basement construction (especially in areas of high groundwater) during winter storms on flood risks and potential storm drain load have not been adequately considered.