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Sewage Tank - Underground Flow Equalization System (UFES) Project

The City of San Mateo plans construction of an underground sewage storage tank right behind Bay Meadows Park in the Event Center Parking Lot.  The City has revised its construction proposal to eliminate the high-noise, high-vibration construction methods (see new city slide set here), but concerns remain:
--If not properly managed, construction methods could damage home foundations. 
--Heavy truck traffic proposed to use Saratoga (instead of the usual Delaware/El Camino truck route):
--On peak days there could be a heavy truck every 2 minutes; more typical days would have trucks every 4-5 minutes
 --would be highly disturbing for Saratoga Ave and Kent Ave. homes
 --poses safety risks for walkers & bikers crossing Saratoga between Bay Meadows and the Whole Foods area
--May be dangerous for commuters picking up buses at the Event Center parking lot.
--There is no plan to handle the construction road closures and truck routes in the context of all of the other Caltrain, city, and private construction in the immediate area
--Both Delaware and Saratoga would be closed during construction
--They propose to entirely close the Delaware/East 28th Ave intersection for weeks right after the Caltrain station moves there AND when the 25th Ave underpass is closed
--Traffic could be a nightmare
--Walking and biking on both Delaware and Saratoga could be dangerous for us and our families
--Construction noise and dust could harm Bay Meadows park users.
--Open trenching proposed on Saratoga and Delaware might harm homes, the street, and underground infrastructure

Written Comments Due May 31.  EVERYONE SHOULD SEND COMMENTS.

Submit Comments to: with cc to and

(1) Thank the City for revising the proposed construction to eliminate the high-noise, high-vibration methods

(2) Protect your personal and your HOA's legal rights:

(3) Request Best Practices to Protect Homes and People:

  • Develop a robust construction traffic, pedestrian, and bike plan to protect residents
  • Route Trucks on El Camino - putting them on Saratoga would be a safety threat 
  • Establish Construction Monitoring Systems to limit home damage and protect public health
  • Protect Bay Meadows Park:  Place limits on construction days and hours and provide robust noise and dust protection
  • No open trenching - risk to Fiesta Gardens homes, streets, and underground infrastructure

More information:

--The Environmental Impact report about the tank is at this link (See first section on webpage - the stuff below is for the whole citywide wastewater rehab project). Full document here [beware! 83MB].
--The Planning Commission materials are here(site plans) and here(presentation slides).

NEXT STEPS (Dates Tentative)

Planning Commission study session 8/27/19

Planning Commission recommendation to City Council 9/24/19

City Council decision 10/7/19

Anticipated construction start Spring 2020

--Main site = Event Center behind pond

--Periodic extended closures of Delaware & Saratoga for excavations


Hillsdale Caltrain Closure September 2019 - Spring 2020 (April)?

Hillsdale new Caltrain station at 28th Ave opening Spring 2020 (April?)

28th Ave and 31st Ave underpasses opening Spring 2020 (April?)

25th Ave RR crossing closed (unknown period) starting Spring 2020 (when underpasses open)

NE Corner E. 28th Ave/ Delaware Sidewalk closed for residential construction (ongoing; end date unknown)

--Pedestrians re-routed to West side of Delaware.  No safe route for bikes

NW Corner E. 28th Ave/ Delaware - office building to be constructed (timing unknown)


Based on experience from other projects in the area, foundation impacts from dewatering could extend 1,000 to 2,000 feet (yellow and orange circles on map below).


What can dewatering & vibration do to buildings?
—Foundations can sink, tilt, or crack, even hundreds of feet away from the construction site.  For a local example, go into buildings at the shopping center at Delaware & Concar, such as the Ross store. Severe foundation subsidence on all buildings on this site (all the way to the Peninsula Ballet Theater on Grant St) is a result of the dewatering for recent construction of the office building on the west side of Delaware (Medallia/450 Concar).
—At a more minor level, vibration & dewatering can affect operation of doors & windows, crack wall boards, and create slight angles in the floor, diminishing property value.
—Dewatering risks depend on many factors, including construction depth (for the tank, 50+ feet), time length (many months), methods used, soil types, methods used (some are more localized than others), and whether an underground groundwater barrier is used.
—Recent construction dewatering at sites in the Bay Meadows area has mostly been shallower and for relatively short periods of time (weeks).  No adverse impacts have been publicly reported.

What are City noise standards?
—Ordinarily, noise should not exceed 70 dBA in residential areas.  This standard is for public health protection.
—During construction, the City allows noise levels up to 90 dBA 50-feet from the noisy equipment.  In recent San Mateo city history, no city-permitted project has every been allowed to violate this standard.  (The city does not have control over Caltrain construction, which violated this standard during the vibratory sheet pile installation at the railroad & E. 28th in winter 2016-17).

Can’t they protect Bay Meadows Park from dust and the noise?
Yes, but they have not proposed very protective measures.  They propose a plywood wall with hay bales and watering down dust twice a day. The Event Center has suggested installation of a stone sound wall (like the ones along Saratoga) between the construction site and the park which would be much better, but even this would not protect homes or the park from the noisiest construction, as the noise would be emitted 50-80 feet in the air (it is emitted where the pile driving hammer hits the post or sheet pile).  Some prior construction has generated waves of dust blowing over Bay Meadows park and into Fiesta Gardens Homes.

How would we file noise or dust complaints or concerns about dewatering impacts?
The city has proposed a telephone line staffed by a live person 24-hours a day, 7-days a week.

What do they propose to do about vibration, noise & dewatering?
They will monitor groundwater levels, noise and vibration, but will only make data public long afterwards, so they can do quality assurance first.  They are planning pre- and post-construction building inspections for some (unspecified) buildings in the area.

When will it happen?  How long will it last?
Construction seems to be anticipated to take  2.5 years. The noisiest construction would take about a year.  Could start spring 2020 (yes, might start when the Caltrain station will be closed). It appears that the noisiest part would be early in the construction period. Construction hours are not currently restricted, though they say they generally plan to work only on weekdays between 7 a.m. and 7 p.m.  They are legally allowed to work 7 am - 7 pm Monday-Friday, 9-5 on Saturday, and 12-4 on Sunday if they want.  They expect to request some exceptions to the allowed work ours for one or more late night/early morning concrete pours.
Mark Eliot,
May 13, 2019, 11:56 AM
Mark Eliot,
May 13, 2019, 11:56 AM
Kelly Moran,
May 27, 2019, 4:06 PM
Mark Eliot,
May 13, 2019, 11:56 AM