HomeMy WebLinkAbout2018-10-15 e-packet@3:00Monday, October 15, 2018
3:00 PM
City of South San Francisco
P.O. Box 711 (City Hall, 400 Grand Avenue)
South San Francisco, CA
City Hall, Large Conference Room - 400 Grand Avenue, South San
Francisco, CA 94080
Environmental Standing Committee of the City Council
Special Meeting Agenda
October 15, 2018Environmental Standing Committee
of the City Council
Special Meeting Agenda
NOTICE IS HEREBY GIVEN, pursuant to Section 54956 of the Government Code of the State of
California, the Environmental Standing Committee of the City of South San Francisco will hold a Special
Meeting on Monday, October 15, 2018, at 3:00 p.m., at City Hall, City Manager's Conference Room, 400
Grand Avenue, South San Francisco, California 94080.
Purpose of the meeting:
Call To Order.
Roll Call.
Public Comments.
MATTERS FOR CONSIDERATION
Motion to approve the Minutes from the meetings of May 22, 2018 and July 24,
2018.
1.
Review of the recommended alternative for the Orange Memorial Park Stormwater
Capture Project. (Justin Lovell, Public Works Administrator and Mo Sharma, Project
Manager)
2.
Adjournment
Page 2 City of South San Francisco Printed on 10/24/2018
City of South San Francisco
Legislation Text
P.O. Box 711 (City Hall, 400
Grand Avenue)
South San Francisco, CA
File #:18-958 Agenda Date:10/15/2018
Version:1 Item #:1.
Motion to approve the Minutes from the meetings of May 22, 2018 and July 24, 2018.
City of South San Francisco Printed on 10/24/2018Page 1 of 1
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City of South San Francisco
Legislation Text
P.O. Box 711 (City Hall, 400
Grand Avenue)
South San Francisco, CA
File #:18-921 Agenda Date:10/15/2018
Version:1 Item #:2.
Review of the recommended alternative for the Orange Memorial Park Stormwater Capture Project.(Justin
Lovell, Public Works Administrator and Mo Sharma, Project Manager)
RECOMMENDATION
It is recommended that the Environmental Standing Committee of the City Council review and provide
feedback on the recommended design alternative for Orange Memorial Park Stormwater Capture
Project (No. sd1801).
BACKGROUND/DISCUSSION
The City Council of South San Francisco approved a Cooperative Implementation Agreement (CIA)with the
California Department of Transportation (Caltrans)in fiscal year (FY)2016-17.Under this agreement,Caltrans
would provide the City $9.5 million for the design,permitting and construction of the Orange Memorial Park
Stormwater Capture project (Project).The Project,at a minimum,must remove trash and pollutants of concern
from storm water run-off from an area equivalent to Caltrans’right-of-way within the Colma Creek watershed
(approximately 23 acres).Subsequently,City Council allocated funds for the initial study,permits and design of
Orange Memorial Park Stormwater Capture Project in the FY 2017-18 Capital Improvement Program (CIP).
The City Council,at its regular meeting on January 24,2018,approved the selection of Lotus Water of San
Francisco,California for the engineering and environmental studies,design,permitting and construction bid
document preparation services for the Project.
The Project will help the City comply with the Regional Water Quality Control Board’s (RWQCB)Municipal
Regional Permit (MRP)which stipulates a regulatory requirement for 100%trash reduction by July 1,2022 and
certain minimum mercury and polychlorinated biphenyl (PCB)load reductions in waters flowing to the San
Francisco Bay.A portion of these load reductions must utilize green infrastructure such as filtration,infiltration,
capture for re-use and trans-evaporation.The Project was initially proposed as a regional project in the San
Mateo Countywide Storm Water Resource Plan (SWRP).
Project Elements
Project components may include the following:
·Capacity for capturing initial storm run-off (approximately six acre-ft.).Initial run-off (first flush)
washes away accumulated pollutants and hence is the most polluted.
·Screens and stilling basins for removing solids exceeding 45 microns.
·PCB,mercury and other pollutant load reduction by bio-treatment,filtration or storm water capture for
non-potable uses.
·Mechanism for collection and disposal of solids removed from storm water flows passing through the
Project site.
·Pumping system for flow diversion and re-use for park irrigation, sewer flushing or other uses.
The Project being considered would generally filter out grit and solids from the creek’s dry-weather and first
flush of wet-weather flows before passing through bio-treatment basins.These processes will remove most
contaminants of concerns listed in the Municipal Regional Permit to the City.Treated water may be allowed to
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contaminants of concerns listed in the Municipal Regional Permit to the City.Treated water may be allowed to
flow to San Francisco Bay or a portion of it may be used for ground infiltration,park and trail irrigation or
another non-potable use.
Project Site Analysis
Lotus Water considered for a potential stormwater capture project the SWRP proposed and previously owned
Mazzanti property near Orange Memorial Park along north and south sides of Colma Creek.Additionally,the
ball fields fronting West Orange Avenue were also considered for the project.As part of the site analysis,Lotus
Water conducted:
·A topographical survey of the aforementioned sites,
·A geotechnical study with borings extending to 45 feet below ground surface, and
·Reviewed a previously completed agricultural pollutants study.
The findings of the project site studies are summarized as follows:
The north and south lots:
a)The top two to three feet of soil is clean fill placed over soil contaminated with agricultural pesticides
and chemicals.
b)The contaminated soil depth is only approximately three feet.Disposal of spoils excavated from this
area would need special consideration.
c)Soil below the clean fill is a part of the poorly graded loose to medium dense sand,silty sand and gravel
extending to a depth of approximately 15.5 to 19 feet below ground surface.This soil layer could liquefy
during a significant earthquake and hence,may not be suitable for supporting a heavy structure such as a
storm water storage facility.
d)A four to five foot thick stiff clay layer was encountered at a depth of approximately 20 feet which
would limit infiltration potential.
The ballfields:
a)The top four and a half to five feet thick medium stiff to stiff clay fill overlaying loose medium dense to
dense alluvial sands and silty or clayey sands.
b)Stiff clay layer,four to five feet thick,was found at an approximate depth of 23 feet limiting potential
ground infiltration.
c)Ground water in March 2018 was at depths of approximately 25 feet.
Project Alternatives
Lotus Water has evaluated three different general concepts as follows:
1)Instream Diversion, Treatment, and Release (Attachment 1)
2)Infiltration Chamber on the north lot (Attachment 2)
3)Water Reuse System under Existing Ballfields (Attachment 3)
Based on site constraints and the thick clay layer found in the soil,Lotus Water determined that an underground
storage facility at the south lot would not be as deep as originally anticipated and would not provide water
treatment capacity required by the CIA.
Alternative 1: Instream Diversion & Release
This concept aims to consolidate improvements in a closed flow-through system located within the existing
channel,taking into account available geotechnical and hydrologic information.Treatment is provided in two
steps:1)above-grade gross solids removal devices (GSRDs)installed within the channel;and 2)a drop inlet
diversion to direct a prescribed flow rate into an inline baffled stilling chamber constructed under the channel
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diversion to direct a prescribed flow rate into an inline baffled stilling chamber constructed under the channel
bed to remove sediment,oil,and grease.Due to the high water table,the system is closed and infiltration is not
feasible; treated flows are instead discharged back into the channel.
This system requires certain hydraulic head to drive flows through the treatment train.A sudden 3.5 foot drop in
the channel grade approximately 500 feet downstream from the upstream project boundary is utilized to create
the needed head.
If it proves easier to construct and maintain the stilling and filtration chambers offline,within the park parcel,
then a variation of this alternative would be to divert flows into the adjacent former greenhouse parcel and
construct the subsurface chambers there along a corridor running parallel to the channel.
Alternative 2: Infiltration Chamber on Former Greenhouse Parcel
This concept carries forward the main components proposed in the SWRP,with some modifications to account
for site conditions.Flows would be diverted via an inflatable rubber dam and drop-inlet diversion with a pump
station.Pumped flows are routed through a hydrodynamic separator for trash and sediment removal and then to
a large infiltration chamber under the northern former greenhouse parcel.Ground water at 15 feet below ground
surface and a thick clay layer just beneath that makes infeasible the deep infiltration facility envisioned in the
SWRP.This modified version of the SWRP project concept includes a shallower facility with its base 5 ft.
below existing ground surface and a much larger footprint to maintain the 6 acre-feet of storage shown in the
SWRP.The larger footprint will increase the contact area,thus increasing the infiltrative capacity of the system
and regenerating capacity between storms more quickly.
As an additional treatment measure to regenerate storage capacity between storms,treated water will be
metered through a filtration chamber to remove particles down to ten microns before discharging back to the
stream through a low-stage orifice at a prescribed flow rate.Following installation of the subsurface chamber,
final surface elevations will be set to support future construction of the children’s playing fields as envisioned
in the park’s Master Plan.
A potential addition to this concept would be to maintain a permanent subsurface reservoir of treated water to
feed a new truck filling station in the parking lot at the entrance to this parcel.
Alternative 3: Diversion to Existing Ballfields for Treatment and Reuse
This concept diverts Colma Creek flows to the softball fields in the southeast corner of the park for treatment
and reuse to satisfy local irrigation demands.Flows are diverted into a drop inlet feeding laterally into a grit
chamber to settle out gross solids at the intake to a gravity-fed diversion pipe running parallel to the channel.
An instream inflatable rubber dam will be necessary to drive flows through the system.A pipe runs downstream
out of the diversion structure until it reaches the pretreatment baffle box just west of the ballfields.Depending
on the depth of the storage system under the baseball/softball fields,a booster pump may also be needed to help
convey diverted flows to the storage area.After course sediment and floatables are removed,the baffle box
discharges into a large storage reservoir underneath the ballfields.A portion of the storage will be a cistern
dedicated to reuse for irrigation,and a portion will be an infiltration gallery to recharge groundwater.If the new
ballfields utilize the EPIC system for an high efficiency subsurface irrigation system,then no additional
treatment is required and treated water will be pumped up for irrigation of the ballfields on an as-needed basis.
If a surface irrigation option is selected, then additional filtration and disinfection would need to be provided.
As an additional treatment measure to regenerate storage capacity between storms in the tanks under the field,
treated water will be metered through a filtration chamber to remove particles down to ten microns before
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treated water will be metered through a filtration chamber to remove particles down to ten microns before
discharging back to the stream through a low-stage orifice at a prescribed flow rate.
Additional funding may be needed for this concept depending on the full trash capture capability,full storage
capacity, type of turf, irrigation system, etc.
Public Outreach
Project concepts were refined with public input received at the following:
July 24, 2018 - meeting of the Environmental Standing Committee of the City Council
September 10, 2018 - community meeting
September 11, 2018 - meeting of the Colma Creek Flood Control District Advisory Committee
September 18, 2018 - meeting of the Parks & Recreation Commission
Comments received at the September meetings generally favored a project at the existing ballfields generally
based on Alternative 3.
Analysis
Alternative 1, estimated construction cost $7.4 million
Alternative 1 is the simplest,which is advantageous in terms of passive operations that do not require any
pumping or electronics.This alternative is contained within the walls of the channel,although a short length of
the channel by the old Mazzanti property will have to be widened from its existing 35-foot width to
approximately 50 feet.Impacts to the park are limited to that minor encroachment around the GSRDs and
minor visual impacts from the pedestrians crossing the downstream bridge.There is no flood reduction,
groundwater recharge,water reuse,or park improvements.Water reuse could potentially be added to this
scenario for an additional cost,pumping water from the outlet of the settling chamber up to a polishing and
disinfection facility housed in a 15 ft x 20-ft equipment structure.
Alternative 2, estimated construction cost $11.4 million
Alternative 2 is not feasible.The geotechnical investigation discovered sandier soils on the north Mazzanti
parcel,as compared to the south parcel where the initial project feasibility investigation was completed in 2016.
The sandier soils increased the susceptibly to liquefaction and differential settling from seismic events.The site
is two miles from the San Andreas Fault.The recommended mitigation measures had an estimated cost of $4
million.Additionally,the Parks &Recreation Department expressed concerns about the future programming
constraints that would result from the underground chamber at this yet-undeveloped site,and CalWater
expressed concerns about the potential introduction of new contaminants into the underlying aquifer that serves
as their drinking water supply. Thus, this alternative was deemed infeasible.
Alternative 3, estimated construction cost $7.4 million
Alternative 3 has the greatest potential to provide a wide range of benefits in addition to improved water
quality.A portion of the subsurface storage will be purposed as a cistern,sized to meet the irrigation demand.
The remaining portion of the storage will be purposed as an infiltration facility.Based on budget constraints
with Caltrans funding,staff is unable to realize the full potential of this alternative,which would be to expand
the size of the project to cover the full ballfield footprint.Another benefit of this alternative if the City can
secure additional funding would be to lower the field several feet to provide flood control benefits.The baseline
version of this alternative provides significant water quality benefits and water reuse for irrigation,but it
includes neither full trash capture nor significant flood reduction benefits.
Based on the criteria developed as part of the project and evaluation of the alternatives,Alternative 3 had the
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Based on the criteria developed as part of the project and evaluation of the alternatives,Alternative 3 had the
best water treatment and reuse benefits which worked within the budget compared to other project alternatives
(attachment 4). Staff is recommending pursuing full design and construction of Alternative 3.
FISCAL IMPACT
The CIA with Caltrans does not allow for additional funding beyond the $9.5 million already secured for the
Project.Staff estimates there is approximately $8 -$8.5 million available for construction,construction
management,and contingency.Any additional funding for other site improvements such as ballfield
renovations or lowering the field for flood control would have to come from other funding sources.There are
sufficient funds at the current cost estimates to cover the construction cost of Alternative 3 as presented.
CONCLUSION
Staff recommends that the Environmental Standing Committee of the City Council review and provide
direction the proposed Alternative 3.Based on the Environmental Standing Committee recommendation,staff
will present the Project to the full City Council for approval.
Attachments:
1.Alternative 1: Instream Diversion & Release
2.Alternative 2: Infiltration Chamber on Former Greenhouse Parcel
3.Alternative 3: Diversion to Existing Ballfields for Treatment and Reuse
4.Alternative Evaluation Matrix
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Project Alternative #1: Instream Alternative in plan view and schematic
Project Alternative #2: Infiltration Alternative in plan view and schematic
Project Alternative #3: Water Reuse Alternative in plan view and schematic
660 Mission Street, 2nd Floor, San Francisco, CA 94105 (415) 800-6805 www.lotuswater.com Project Concept Alternatives Evaluation Matrix