HomeMy WebLinkAbout07.b. Receive update on DSRSD-EBMUD Recycled Water Authority (DERWA) request to develop an MOU for a pilot project to divert raw wastewater to meet peak summer irrigation demand Page 1 of 31
Item 7.b.
Central Contra Costa Sanitary District
March 1, 2018
TO: HONORABLE BOARD OF DIRECTORS
FROM: MELODY LABELLA, RESOURCE RECOVERY PROGRAM MANAGER
REVIEWED BY: JEAN-MARC PETIT, DIRECTOR OF ENGINEERING AND TECHNICAL
SERVICES
ROGER S. BAILEY, GENERAL MANAGER
SUBJECT: RECEIVE UPDATE ON DUBLIN SAN RAMON SERVICES DISTRICT-EAST
BAYMUNICIPAL UTILITYDISTRICT RECYCLED WATERAUTHORITY
(DERWA) REQUEST TO DEVELOP A MEMORANDUM OF
UNDERSTANDING FORA PILOT PROJECTTO DIVERT RAW
WASTEWATER FROM CENTRAL SAN'S SERVICE AREA FOR THE
PURPOSE OF PRODUCING RECYCLED WATER TO MEET DERWA'S
PEAK SUMMER IRRIGATION DEMAND
In January2017, Central San received a letterfrom the Dublin San Ramon Services District (DSRSD)—
East Bay Municipal Utility District (EBMUD) Recycled Water Authority (DERWA) requesting development
of a memorandum of understanding (MOU)to explore a potential partnership and pilot project to divert a
portion of the raw wastewater from Central San's San Ramon Pump Station between May and September
everyyear. The wastewater would be diverted through DSRSD's existing collection system to DSRSD's
treatment plant, for the purpose of producing and distributing recycled water to meet DERWA's peak
summer irrigation demand. According to the letter, DERWA made this request due to the need for a
temporary supplemental supply to helpmeet recycled water demands in the EBMUD and DSRSD service
areas until wastewater flows increase with development and other long-term options are identified.
In March 2017, staff brought this issue to the Real Estate Environmental and Planning (REEP) Committee
for discussion. At that meeting, the Committee indicated that additional information is needed to determine
how to divert the water and what the impacts would be to Central San. The Committee directed staff to
continue strategizing with DERWA and return with a proposed plan at a future Committee meeting.
After collaborating with DSRSD staff to evaluate diversion options, in addition to having internal
discussions on how the potential diversions will impact Central San's operation and future recycled water
projects, Central San staff brought this issue back to the REEP Committee in December 2017. At that
meeting, the Committee recommended bringing this update to the full Board before staff performs further
work on this proposed project.
For comprehensive background on this diversion request, please refer to Attachments 1 and 2 to this
memo for the prior REEP Committee memos.
March 1, 2018 Regular Board Meeting Agenda Packet- Page 131 of 225
Page 2 of 31
ATTACHMENTS:
1. March 22, 2017, REEP Committee Memo on DERWA Diversion Request
2. December 18, 2017, REEP Committee Update Memo on DERWA Diversion Request
3. Presentation
March 1, 2018 Regular Board Meeting Agenda Packet- Page 132 of 225
Attachm'@df of 31
Central Contra Costa Sanitary District
March 22, 2017
TO: REAL ESTATE, ENVIRONMENTAL & PLANNING OMMITTEE
VIA: ROGER S. BAILEY, GENERAL MANAGER `
JEAN-MARC�TIT, DIRECTOR OF ENGINEERING & TECHNICAL
SERVICES 3%19
PHILIP LEIBER, DIRECTOR OF FINANCE & ADMINISTRATION
DANEA GEMMELL, PLANNING & DEVELOPMENT SERVICES
DIVISION MANAGER
REVIEWED
BY: KENT ALM, DISTRICT COUNSEL
FROM: MELODY LABELLA, RESOURCE RECOVERY PROGRAM MANAGER9V\'Y--
THOMAS BRIGHTBILL, SENIOR ENGINEER UDC\.,g-
DAN FROST, SENIOR ENGINEER 0�4 (;I.
SUBJECT: DERWA REQUEST TO DEVELOP A MEMORANDUM OF
UNDERSTANDING FOR A PILOT PROJECT TO DIVERT RAW
WASTEWATER FROM CENTRAL SAN'S SERVICE AREA FOR THE
PURPOSE OF PRODUCING RECYCLED WATER TO MEET DERWA'S
PEAK SUMMER IRRIGATION DEMAND
Introduction
Central San has received a written request (see Attachment 1) from the Dublin San
Ramon Services District (DSRSD) - East Bay Municipal Utility District (EBMUD)
Recycled Water Authority (DERWA) to develop a memorandum of understanding
(MOU) to explore a potential partnership and pilot project to divert a portion of the raw
wastewater from Central San's San Ramon Pump Station between May and September
every year. The wastewater would be diverted through DSRSD's existing collection
system to DSRSD's treatment plant, for the purpose of producing and distributing
recycled water to meet DERWA's peak summer irrigation demand. DERWA is now
making this request, because it has a need for a temporary supplemental supply to help
meet recycled water demands in the EBMUD and DSRSD service areas until
wastewater flows increase with development and other long-term options are identified.
Since exploring partnerships to augment the region's water supply is an important
strategic goal for Central San, this pilot project provides an excellent opportunity for
Central San to consider for expanding the beneficial reuse of its wastewater.
N:\ENG BOARD DOCS\Board Committee Meetings\BEEP Committee\2017\March\3-22-17 BEEP Memo-DERWA Diversion
Rvsd.docx
March 1, 2018 Regular Board Meeting Agenda Packet- Page 133 of 225
Page 4 of 31
Real Estate, Environmental and Planning Committee
March 22, 2017
Page 2of5
Background
DERWA created the San Ramon Valley Recycled Water Program (SRVRWP) in 1995,
and began delivering recycled water in early 2006. The SRVRWP consists of the
treatment, storage, and use of highly-treated recycled water for landscape irrigation
within parts of Dublin and San Ramon (see Attachment 2). The SRVRWP is being
implemented in several phases within the two Districts' existing service areas. Future
phases of the program will extend recycled water into other parts of the San Ramon
Valley, depending on supply and demand, capital funding needs and availability. The
SRVRWP is designed to provide up to 3,696 acre-feet (>1 billion gallons) per year of
recycled water to DSRSD, and up to 2,688 acre-feet (>875 million gallons) per year of
recycled water to EBMUD.
EBMUD and DSRSD take the recycled water from the DERWA backbone system and
provide it to recycled water customers in their respective service areas delivering it via
distribution pipelines. DSRSD currently supplies DERWA recycled water to parts of
Dublin and the Dougherty Valley, while EBMUD serves DERWA recycled water to
portions of San Ramon. In future phases, EBMUD will also supply areas within
Blackhawk and Danville. The SRVRWP's main transmission pipeline connects to
DSRSD and the EBMUD pipelines that serve large irrigation customers: golf courses,
parks, greenbelts, roadway medians, schools, office complexes, and common areas in
homeowner associations.
In 2014, the City of Pleasanton signed agreements with the SRVRWP partners that
allow its treated wastewater to be used to produce recycled water. The agreements
pave the way for a recycled water program in Pleasanton and expansion of the
SRVRWP water recycling plant. As the City of Pleasanton's recycled water program is
implemented, DERWA will face supply shortages, since the DERWA partners are
currently using the City of Pleasanton's wastewater to produce a portion of DERWA's
recycled water currently being used in DSRSD's and EBMUD's service areas. In an
effort to address the anticipated future shortage, DERWA first evaluated the concept of
diverting Central San's raw wastewater flow in 2004.
Analysis
In considering the DERWA request to divert wastewater from Central San's service
area, staff identified potential benefits and issues of concern from such an arrangement.
The potential benefits are
• Expanded beneficial reuse of Central San's wastewater
• Reduced treated wastewater discharges to Suisun Bay
• Preserving recycled water service to Central San's customers in San Ramon
Staff identified the potential consequences as:
• Collection system and treatment plant impacts
• Conflicts with Board recycled water goals
• Customer and financial impacts
March 1, 2018 Regular Board Meeting Agenda Packet- Page 134 of 225
Page 5 of 31
Real Estate, Environmental and Planning Committee
March 22, 2017
Page 3 of 5
Staff expands on the potential benefits and consequences below.
Potential Benefits
The DERWA diversion request seeks raw wastewater flow from the San Ramon Pump
Station, between the months of May and September. During that timeframe, the
average daily wastewater flow through that Pump Station is 2.5 million gallons per day
(MGD). By diverting that flow, an additional 2.5 MGD of Central San's wastewater will
be put to beneficial use, more than doubling the amount of recycled water produced
from Central San's wastewater. This would also mean a corresponding reduction in
treated wastewater effluent being discharged into Suisun Bay.
In addition, since EBMUD and DSRSD have been essentially "borrowing" wastewater
flow from the City of Pleasanton to meet the current DERWA demand for recycled
water, now that the City of Pleasanton is developing their own recycled water program,
both EBMUD and DSRSD need to find additional supply to meet DERWA recycled
water demands in their respective service areas. Since EBMUD and DSRSD serve
recycled water to the southern portion of Central San's service area, the diverted
wastewater flow from the San Ramon Pump station could be viewed as preserving
recycled water service to current (and potentially future) Central San customers using
recycled water produced by DERWA.
Potential Consequences
Potential Physical Impacts — Collection System and Treatment Plant
Maintaining the functionality of Central San's collection system is an important
consideration in evaluating raw wastewater diversion requests. Due to dramatic
improvements in the water-use efficiency of indoor water fixtures, expanded graywater
use, and other water conservation efforts, Central San's base wastewater flows have
declined far more rapidly over the last 30 years than the collection system has been
replaced, resulting in many pipelines that are oversized for handling summer
wastewater flows. According to Central San's new calibrated dynamic collection system
hydraulic model, many of Central San's pipelines run below scouring velocity during dry
weather. The reduction in wastewater flow in an oversized pipe can lead to the settling
of solids in the collection system resulting in increased potential for odors and corrosion,
stoppages, and other potential consequences on wastewater quality and downstream
treatment plant impacts that may not have been fully realized or fully correlated yet.
The recent drought has provided insights into potential treatment plant impacts from
reduced wastewater flows. In 2014 and 2015, the average influent flow declined below
30 MGD for Central San's treatment plant, which has a permitted capacity of 53.8 MGD.
Hourly flows throughout the day reduced to as low as 11.5 MGD during the summer.
This decline in flow presents operational challenges for facilities originally designed for
higher flows (inadequate turndown). So far, these challenges have not caused any
process shutdowns and staff has reliably maintained treatment performance and
compliance; however, it is important not to lose sight of potential unintended
consequences of further reducing flow to the treatment plant. When flows are already
March 1, 2018 Regular Board Meeting Agenda Packet- Page 135 of 225
Page 6 of 31
Real Estate, Environmental and Planning Committee
March 22, 2017
Page 4of5
severely low and impacts of these low flows affecting treatment plant facilities are
already present, increased diversion of raw wastewater would exacerbate these issues.
Potential Conflict with Board Recycled Water Goals
During preparation of Central San's Wholesale Recycled Water Opportunities Study
(Wholesale Study), the Real Estate, Environmental and Planning(BEEP) Committee
provided guidance to staff to favor the development of recycled water projects with large
yields and year-round demand. The DERWA diversion requests seeks a small volume
of Central San's raw wastewater to produce recycled water for seasonal irrigation
demand.
The Comprehensive Wastewater Master Plan carried forward the potential alternatives
from the Wholesale Study and included the facilities, locations, and costs, if Central San
were to pursue zero discharge of treated wastewater effluent during dry weather
conditions. Future potential recycled water projects include supply of up to 5.8 MGD of
recycled water to the Concord Reuse Project, up to 20 MGD of recycled water to nearby
refineries, and up to an additional 10 MGD of recycled water for an indirect or direct
potable reuse project.
To provide a reliable supply of recycled water to any of these Board-supported projects,
it is critical that adequate wastewater is available to those recycled water treatment
facilities. At the plant's already low hourly flows of 11.5 MGD, it will become challenging
to provide a reliable supply of treated wastewater to several treatment process trains
without triggering a significant increase in onsite storage facilities. Allowing additional
diversion of raw wastewater may unintentionally influence the unit cost, and therefore
the feasibility, of some of Central San's large, regional recycled water projects
envisioned at the treatment plant.
Potential Customer and Financial Impacts
Providing reliable wastewater service at equitable rates that comply with Proposition
218 creates a complex, interdependent system, where heavy capital investments are
required to rehabilitate and replace necessary infrastructure. Making a change to where
a customer's wastewater is ultimately treated has corresponding complex and
interdependent impacts. Staff has conducted a preliminary financial analysis of the
impacts to Central San from a potential diversion of 2.5 MGD of raw wastewater flow to
DSRSD for the purpose of producing recycled water for DERWA.
Geographic Information System (GIS) data was analyzed to identify all of the parcels
which contribute flow to the San Ramon Pump Station. There are 12,864 billable
parcels, of which 11,161 are single-family residential, 16 are single family/multifamily
residential (30 residential unit equivalents (RUEs)), 1,643 are multifamily residential
parcels (4,360 RUEs), and 44 are non-residential parcels (1,604 RUEs). Staff
estimates that there are roughly an additional 600-1,000 RUEs that could be added to
the sewershed flowing to the San Ramon Pump Station. The total 2015/2016 sewer
service charge (SSC) revenue to Central San for the developed parcels is $8,559,973,
which represents 11.9% of Central San's total 2015/2016 SSC revenue. Property tax
March 1, 2018 Regular Board Meeting Agenda Packet- Page 136 of 225
Page 7 of 31
Real Estate, Environmental and Planning Committee
March 22, 2017
Page 5of5
revenue associated with these parcels, which Central San directs to the capital
program, is another $1.4 million (the size of which would not vary from this loss of flow).
Dividing the $8,559,973 total SSC revenue by the 2015/2016 rate of $503 per single
family residence yields 17,018 RUEs, which is approximately 8% of the total flow at the
treatment plant. Central San staff identified the following treatment plant costs as
variable: grit removal, chemicals, utilities, and ash disposal. Based on 2015/2016 costs
and treated wastewater flows, these variable costs are about $294 per million gallons.
Multiplying this figure by 2.5 MGD for 365 days results in an estimated variable cost of
$268,275 (3.13% of total SSC revenue from these parcels). Multiplying this by 5/12 to
capture the May— September timeframe requested, the variable costs would fall to
$111,781 (1.31% of total SSC revenue from these parcels).
If revenues are to be shared with DSRSD for the treatment of the diverted wastewater
flow, $111,781 represents the upper limit of revenue that could be shared (assuming the
diversion doesn't cause additional operational expenses) without raising costs to other
Central San customers from having them bear the lost share of fixed cost recovery.
Alternatively, if the full SSC revenue associated with these flows were provided to
DSRSD, Central San's remaining customers would face a 13.1% increase (at 2.5 MGD)
in their SSC bills as a result. This would require Central San to increase its annual
charge from $503 to $569 (13.1%) per RUE to address revenue shortfalls.
Discussion
While Central San is highly supportive of expanding the beneficial reuse of its
wastewater, there are potentially significant consequences that could result from
diverting raw wastewater to DSRSD that need to be carefully considered. Alternatively,
the most optimal way for Central San to provide water supply to DERWA is through a
regional exchange. For example, Central San could provide recycled water to one or
both Martinez refineries and that freed water supply could be transferred to Zone 7, the
wholesale water retailer in the San Ramon Valley, and ultimately provided to DERWA.
The end user of the water would contribute financially to the Refinery Project, along with
other potential project partners, in order to keep Contra Costa Water District financially
whole. Such a large-scale project would result in greater efficiencies, align with Board
recycled water goals, lead the way on regional interagency collaboration among water
agencies, and create water supply that could be used to meet potable or irrigation
demands.
Staff will be available at the March 22, 2017, REEP Committee meeting to discuss this
request and receive direction.
Attached Supporting Documents:
1. DERWA Letter Dated 1/27/17.• Temporary Wastewater Flow Diversion Concept
2. DERWA Facilities Map
March 1, 2018 Regular Board Meeting Agenda Packet- Page 137 of 225
Page 8 of 31
Attachment 1
DERWA
DSRSD-EBMUD Rwyc&d WATER AurhoRny
PARTNERS%N WATER REcycGNq
January 24, 2017
Racefytiad
Roger S. Bailey, General Manager
Central Contra Costa Sanitary District JAN 7 201
5019 Imhoff Place
Martinez, CA 94553 �ojc�� YC/
Subject: Temporary Wastewater Flow Diversion Concept
Dear Mr. Bailey:
Earlier this month, Dan McIntyre of Dublin San Ramon Services District(DSRSD), discussed with
you the concept of diverting a portion of Central Contra Costa Sanitary District's(CCCSD)
wastewater from south San Ramon and Dougherty Valley to DSRSD to help meet peak demands of
the DSRSD --East Bay Municipal Utility District (EBMUD) Recycled Water Authority (DERWA)
system. DERWA is interested in exploring this opportunity with CCCSD.
DERWA has a need for a temporary supplemental supply during the peak irrigation season to help
meet demands in the EBMUD and DSRSD service areas until wastewater flows increase with
development and other long-term options are identified. The average daily wastewater flow from
Dougherty Valley and south San Ramon from May to September is approximately 2.5 million gallons
per day. DERWA would like to explore diverting a portion of this flow from CCCSD's San Ramon
Pump Station during the irrigation season through a pilot project in partnership with CCCSD. This
wastewater diversion concept has mutual benefits to both DERWA and CCCSD including reducing
wastewater discharge, meeting peak recycled water demands, and optimizing water recycling in the
region.
To explore this potential partnership and pilot project,DERWA would like to develop a
memorandum of understanding (MOU)with CCCSD. I understand that a CCCSD/DSRSD liaison
meeting will be scheduled in late February, and will offer an opportunity to communicate at an
elected official level about a potential partnership.
I propose we schedule a meeting in early February to discuss our mutual interests and next steps.
If you have any questions or would like discuss developing the MOU, please contact me at 510-287-
0125 or michael.tognolini@ebmud.com.
Sincerely,
Michael T. Tognolini
Authority Manager
cc: Dan McIntyre, DSRSD
V OERWAXAgreements\Supplemental Supply Agreements-CCCSDIDERWA Letter io CCCSD Wastewater Diversion Concept docX
7051 DubhN 1BOUIEVARd, Dublin, CA 94568.3018 • (925) 828-0515
March 1, 2018 Regular Board Meeting Agenda Packet- Page 138 of 225
Attachment 'I
DERWA San Ramon Valley
Recycled Water Program
Current Facilities
Location Map (April 2016)
EBMUD
Service Area
Pump Station R4000
(Future)
Camino Tassajara
I
I
Pump Station R3000 Reservoir R3000
(Future)
C{°'N�anlpP Fd
Pump Station R300B
c
0
O
✓Pr
l�
Page 9 of 31
aR
Inde Bim,F
8°t��n9e�Car+ Reservoir R300
Pump Station R300 `'
d�
w /
o /
Csta Cour /
�� Contra �ntY
/Meda C0
/ Tassajara Reservoir ReservoiK.
Pump Station R20
�o
o;
0
Duplin BNd
nterstate 580
Owens Or
1 1
Dr
Pump Station
N
r
Pleasanton Agency Responsible For
Facility Operations&Maintenance
y
Sergi$n °pyo
li DERWA Backbone DSRSD
� a
DSRSD Recycled Water DSRSD
EBMUD Recycled Water EBMUD
Pleasanton Recycled Water Pleasanton
EBMUD Pleasanton 0 EBMUD t Pleasanton Facility 0 Facility
DERWA DSRSD
o Facility E Facility DSRSD
'o
Hemallve DSRSD Water Service Area DSRSD
a Pleasanton Water Service Area Pleasanton
'o EBMUD
EBMUD Water
A Service Area E...Pt DERWA!—k—.P"—,
n......1..!moa A200,.De
Pump llwtlan 0.20DA
O
March 1, 2018 Regular Board Meeting Agenda Packet- Page 139 of 225
�O -
S
«gin �
Ps
PsSan Ramon Pump Station
Sewer Mains Tributary to
San Ramon Pump Station
ED Central San
Boundary
r
-D Boundary
San Ramon City Limitr r
� SSan Ramon Pump Station Sewershed
Protecting Public Health art d the Environment
1 i -'• :•. • •W•- •. - -.•' R1 •
Page 1'b6V31
Attachment 2
Central Contra Costa Sanitary District
December 18, 2017
TO: REAL ESTATE, ENVIRONMENTALAND PLANNING COMMITTEE
FROM: MELODY LABELLA, RESOURCE RECOVERY PROGRAM MANAGER
REVIEWED BY: JEAN-MARC PETIT, DIRECTOR OF ENGINEERING AND TECHNICAL
SERVICES
ROGER S. BAILEY GENERAL MANAGER
SUBJECT: RECEIVE UPDATE ON DUBLIN SAN RAMON SERVICES DISTRICT-EAST
BAYMUNICIPAL UTILITYDISTRICT RECYCLED WATERAUTHORITY
(DERWA) REQUEST TO DEVELOP A MEMORANDUM OF
UNDERSTANDING FORA PILOT PROJECT TO DIVERT RAW
WASTEWATER FROM CENTRAL SAN'S SERVICE AREA FOR THE
PURPOSE OF PRODUCING RECYCLED WATER TO MEET DERWA'S
PEAK SUMMER IRRIGATION DEMAND
Background
In January2017, Central San received a letterfrom the Dublin San Ramon Services District (DSRSD)—
East Bay Municipal Utility District (EBMUD) Recycled Water Authority(DERWA) requesting development
of a memorandum of understanding (MOU)to explore a potential partnership and pilot project to divert a
portion of the raw wastewater from Central San's San Ramon Pump Station between May and September
every year. The wastewater would be diverted through DSRSD's existing collection system to DSRSD's
treatment plant, for the purpose of producing and distributing recycled water to meet DERWA's peak
summer irrigation demand. According to the letter, DERWA made this request due to the need for a
temporary supplemental supply to helpmeet recycled water demands in the EBMUD and DSRSD
service areas until wastewater flows increase with development and other long-term options are identified.
n March 2017, staff brought this issue to the REEP Committee for discussion. At that meeting, the
Committee indicated that additional information is needed to determine how to divert the water and what
the impacts would be to Central San. The Committee directed staff to continue strategizing with DERWA
and return with a proposed plan at a future Committee meeting.
Central San staff has been working with DSRSD staff to evaluate diversion options, in addition to having
internal discussions on how the potential diversions will impact Central San's operation and future recycled
water projects. Staff is returning to update the Committee on these efforts.
Diversion Alternatives
n October 2017, DSRSD staff, with support from their consultant West Yost, presented five diversion
DleceWte2013$2WjUFAE8Ra@bfdeAeg Mgehdg Rgekda Plagffifl4FPa*(2Z6of 31
Page 226V31
alternatives to Central San staff, which ranged from a simple gravity diversion using the existing
emergency overflow interconnection between Central San's and DSRSD's collection system, to building a
DERWA pump station adjacent to Central San's. Central San and DSRSD staff worked together to
narrow these five alternatives down to two gravity diversion options and further refine the interconnection
and operational details for each. Central San's Engineering and Operations staff have been meeting
internally to review these two alternatives, evaluate their potential impacts, and determine how the potential
impacts could be mitigated.
Diversion Alternative 2 would divert all the incoming dry weather wastewater flow to the San Ramon Pump
Station by modifying the existing overflow interconnection between Central San's and DSRSD's collection
systems. This option would involve closing the influent gate into the pump station, which has been pinned
open (not exercised) since the 1990s, when a large sanitary sewer overflow to the adjacent creek occurred
due to that gate failing to open fully after being temporarily closed. Diversion Alternative 4 would modify
the existing emergency overflow interconnection between Central San's and DSRSD's collection system
to divert approximately 1.5 million gallons per day(MGD) of dry weather flow from the west side of the San
Ramon Pump Station. Schematics of the two diversion alternatives are presented in Attachments 1 and 2.
An overview of the two diversion alternatives, including DERWA pros and cons and Central San
operational and policy concerns, are presented in Attachment 3.
Discussion
While Central San is highly supportive of expanding the beneficial reuse of its wastewater, there are
significant consequences that could result from allowing DERWA to divert Central San's raw wastewater
supply. I n particular, staff's biggest concern is that once DERWA comes to rely on Central San's
wastewater flow, it will always be reliant upon it, making it unavailable for large-scale recycled water
projects at Central San's main treatment plant. For example, during dry weather drought conditions,
Central San has approximately 25 MGD of wastewater available for producing additional recycled water.
The Refinery Recycled Water Project demand is 20 MGD; however, 24 MGD would be needed to yield
20 MGD of recycled water due to the production efficiency of advanced treatment processes. Beyond
that, Central San would need additional treated wastewater to dilute the concentrated brine created from
the reverse osmosis process prior to discharge, requiring even more wastewater flow. I n other words,
Central San is going to need every drop of wastewater in the summer months in order to reliably serve the
full Refinery Project.
When asked about the length of time DERWA would need Central San's raw wastewater supply, DSRSD
staff has indicated that it would be until enough additional wastewater is generated from new development
in the areas that DSRSD serves.According to DSRSD's Master Plan, it will take approximately 10 years
to generate the amount of wastewater that would be diverted under Diversion Alternative 4 and even longer
to replace the amount of wastewater that would be diverted under Diversion Alternative 2.
Conclusion
Due to the significance of the potential operational and policy-related impacts that could result from
Diversion Alternatives 2 and 4, staff recommends not moving forward on any permanent infrastructure
modifications to allow for the diversion of Central San's raw wastewater to DERWA. However, if the
Committee wishes to pursue this request from DERWA further, a diversion pilot project could be
considered. A temporary sump pump could be installed in the bottom of Central San's manhole (manhole
11) immediately upstream of the interconnection with DSRSD's collection system to lift a portion of
the wastewater from Central San's collection system into DSRSD's collection system. Conducting this
pilot would allow DERWA to obtain additional wastewater flow, while allowing Central Santo evaluate
localized and system-wide impacts without significant investment by DERWA.
Staff looks forward to discussing this updated information and receiving your direction at the December
DleceWte2013$2WjUFAE8Ra@bfdmdeg Mgehdg Rigel t14242Mof 31
Page 336V31
18, 2017, REEP Committee meeting.
GOAL ONE: Provide Exceptional Customer Service
Strategy 2- Improve Interdepartmental Collaboration
GOAL SIX: Embrace Technology, Innovation and Environmental Sustainability
Strategy 1 -Augment the Region's Water Supply
ATTACHMENTS:
1.Attachment A- Schematic of Diversion Alternative 2
2.Attachment B - Schematic of Diversion Alternative 4
3.Attachment C - Overview of Diversion Alternatives 2 & 4
Dlecelmtje2013$ FABB@a@bfdmttdag Mgehdg Rgekda t14?4225of 31
ATTACHMENT A
QMH
17 24" VCP
MH MH
16 15
Close
G 101 I
Close
G102
18 Force —
v
Main Open Qj
G103 I >
J = 0
14" Force Main LARWIN
PUMP STATION MH
10
12" Force Main
24" Force Main 18" Force Main
Surge N
Tank
00
MH
- - - - - - - - - - - - - - - - - - - - - - 18" Sewer 11
Figure 5
Dublin San Ramon Services District
Larwin Pump Station Diversion Alternatives '"EST .OST
�SSOCI�SES
10/17/2017 ALTERNATIVE 2 SCHEMATIC
ATTACHMENT B
17 24" VCP '
MH _ _ _ _ MH
18" Force Main 16 15
Oil LARWIN '
14" Force Main PUMP STATION
12" Force Main
Surge
14 O 18" Force Main Tank N
24" Force Main 00
New
1 High Existing 18" Plug
Manhole 10 Level Valve
L Bypass
4 DSRSD
MH
MH
- - - - - - - - - - - - - - - - -
18" Sewer 11 � 18" Sewer — �
'A,- -*�- -4,,- - -
Figure 7
Dublin San Ramon Services District
Larwin Pump Station Diversion Alternatives '"EST .OST
�SSOCI�SES
11/13/2017 ALTERNATIVE 4 SCHEMATIC
Page ft6V31
Attachment C — Overview of Diversion Alternatives 2 and 4
DERWA Description Construction DERWA Pros DERWA Cons Central San Operational and Policy Concerns
Alternative Requirements
2 Gravity Bypass of New high-level overflow . No new creek crossing • Poor flow control This option is not recommended by staff for further consideration due to the following
Existing PS by Closing line from manhole (MH) • Does not require a new • No flow metering concerns.
Inlet Gate and Raising #10 back to the pump MH
Hydraulic Grade station . CCCSD can schedule Operational Concerns:
maintenance activities
inside pump station for An overflow at this Pump Station many years ago led to commitments made by
months when gate is Central San to San Ramon's City Council to prevent future overflows. As a result,
closed and risk of the Pump Station's inlet gate was pinned open at the direction of Central San's
overflow is lowest management at that time. Serious concerns about closing the inlet gate and
causing another overflow, should the gate not fully reopen. If a new inlet gate is
proposed, there is the same concern that the gate could fail in a closed or partially
closed position causing an overflow.
• Unknown upstream hydraulic impacts by doing gravity diversion. We have not
modeled this scenario to see the resulting hydraulic grade line (HGL). The
estimated impact on the new upstream HGL rising by 5 feet was developed by
DERWA's consultant and needs to be validated by Central San.
• Taking all the dry weather flow would result in keeping the Pump Station offline,
crippling its ability to respond quickly to a rapid increase in incoming flow should
the new diversion become blocked.
• Potential for deposition in the inverted siphon during low flows (night).
• Potential downstream gravity sewer impacts due to less flow and possible solids
deposition.
• Potential forcemain odors and corrosion issues due to not being operated and no
corrosion/odor control operating. Potential issues with valves on forcemain piping.
• Requires extra resources (staff and materials) to address flushing and odor
concerns with the forcemains and gravity sewers. Difficult to predict exactly how
much until in operation.
• Reduced flow creates further challenges with operating the existing wastewater
treatment plant during low flow conditions and challenges with implementing future
nutrient removal and recycled water facilities (less water available impacts both
operation and storage needs).
Policy Concerns:
• Diverting this flow will reduce the volume of treated wastewater available at
Central San's treatment plant, which would reduce the volume available to serve
the Refinery Project and to diluting the resulting brine, making the project more
expensive (due to added storage) and possibly infeasible to fully implement.
• Diverting the flow reduces volume for all recycled water projects and customers
and may trigger more expensive recycled water projects all around.
• Possible impact on pump zone fee currently in development.
• Possible long-term service area implications
Page 1 of 2
Mecehnibe2C113$E450URE8@aEabi mifieg Mgehdg Rgekmlla-Reoffit14F4i2M of 31
Page TW31
Attachment C — Overview of Diversion Alternatives 2 and 4
DERWA Description Construction DERWA Pros DERWA Cons Central San Operational and Policy Concerns
Alternative Requirements
4 Gravity Diversion at • New MH between MH 11 • No new creek crossing • Only flow from MH This option is not recommended by staff for further consideration due to the following
MH 11 and MH 10 • Maintains ability for high- 11 is available for concerns.
• New 18" sewer pipe from level gravity bypass to diversion
MH 10 to DSRSD MH DSRSD in the event of a • Poor flow control Operational Concerns:
• New 18" sewer pipe from failure at the Pump • No flow metering
MH 10 to the new MH Station • This alternative may be technically feasible but there are many concerns that need
• Fill 18" sewer between • No modifications to the to be further explored and addressed. Overall there are risks and challenges we
MH 11 and new MH existing Pump Station will not be able to identify until a diversion is operational.
• New gate valves in • All construction on the • This option will divert half the flow coming into the Pump Station, which would
gravity sewer lines trail side of the creek require operating the existing pumps in a way that we do not currently operate.
Increased wear and potential pump issues with cycling pumps with variable
frequency drives that are oversized for the reduced flow. May require new pumps
and controls, which there may not be enough space for. Replacing existing
pump(s) with smaller ones is not acceptable because it would impact the reliable
pumping capacity for the pump station.
• Odors are a major concern for residents in this area. Increasing residence time in
the Pump Station (due to lower flows) could increase the potential for odors.
• New potential failure points (manholes and valves) being installed adjacent to a
creek would raise Central San's risk of overflows in an environmentally-sensitive
area.
• Installation of gate valves in gravity line not ideal, and hard to maintain or access in
the future. Valve access and maintenance is a concern. One risk is that we are
unable to open valve at end of summer and cannot convey wet weather flows to
the pump station.
• Reduced flow creates further challenges with operating the existing wastewater
treatment plant during low flow conditions and challenges with implementing future
nutrient removal and recycled water facilities (less water available impacts both
operation and storage needs).
Policy Concerns:
• Diverting this flow will reduce the volume of treated wastewater available at Central
San's treatment plant, which would reduce the volume available to serve the
Refinery Project and to diluting the resulting brine, making the project more
expensive (due to added storage) and possibly infeasible to fully implement.
• Diverting the flow reduces volume for all recycled water projects and customers
and may trigger more expensive recycled water projects all around.
• Possible impact on pump zone fee currently in development.
• Possible long-term service area implications
Page 2of2
9ecehnibe2Cl1l3$E45JUREBR Sabi mifieg Mgehdg Rgekmlla-Reoffitl4P4i2219 of 31
Attachment 3
UPDATE ON DERWA
RAw WASTEWATER
DIVERSION REQUEST
Melody LaBella, P. E.
Resource Recovery Program Manager
Board Meeting
March 1 , 2018
_ f
March 1, 201 rd Meeting - 14A nf
PREOENTATION OVERVIEW
Background
Dublin San Ramon Services District (DSRSD)
— East Bay Municipal Utility District (EBMUD)
Recycled Water Authority (DERWA)
City of Pleasanton
DERWAs Diversion Request
Central San 's Efforts to Date
Diversion Alternatives
Diversion Pros and Cons
Questions/Board Input
1
nERWA
DERWA created the San Ramon Valley
Recycled Water Program (SRVRWP ) in
1995 and began delivering recycled
water in 2006 .
It has been known since inception that
DERWA would face supply shortages .
DERWA first evaluated the concept of
diverting Central San's raw wastewater
flow in 2004 .
1
SRVRWP
Being implemented in several phases within
DERWAs existing service areas
Future phases will extend recycled water into
other parts of the San Ramon Valley,
depending on supply and demand and capital
funding needs and availability
Designed to provide :
Up to 3,696 acre-feet (> 1 billion gallons) per year
of recycled water to DSRSD's service area
Up to 2 ,688 acre-feet (>875 million gallons) per
year of recycled water to EBMUD's service area
1
Pl-,EASANTON
In 2014, the City of Pleasanton signed agreements
with the DERWA partners for its wastewater to be
used to produce recycled water.
The agreements pave the way for a recycled water
program in Pleasanton and expansion of the
SRVRWP water recycling plant.
As the City of Pleasanton's recycled water
program is implemented , DERWA will face supply
shortages, since the DERWA partners are
currently using Pleasanton's wastewater to
produce a portion of DERWA's recycled water
currently being used in DSRSD's and EBMUD's
service areas.
1
DERWA' s DIVERSION REOHEST
In January 2017, Central San received a written request from
DERWA to develop a memorandum of understanding to
explore a pilot project to divert a portion of the raw wastewater
from the San Ramon Pump Station from May through
September every year.
The wastewater would be diverted through DSRSD's existing
collection system to DSRSD's treatment plant, for the purpose
of producing and distributing recycled water to meet DERWA's
peak summer irrigation demand.
DERWA is now making this request, because it has a need for
a temporary supplemental supply to help meet recycled water
demands in the EBMUD and DSRSD service areas until
wastewater flows increase with development and other long-
term supply options are identified .
1
CENTRAL SAN ' S EFFORTS TO DATE
In March 2017 , staff first brought this issue to
the Real Estate , Environmental & Planning
Committee for discussion .
At that meeting , the Committee indicated that
additional information is needed to determine
how to divert the water and what the impacts
would be to Central San .
The Committee directed staff to continue
strategizing with DERWA and return with a
proposed plan at a future Committee
meeting .
1
CENTRAL SAN ' S EFFORTS TO DATE
- In October 2017 , DSRSD staff and their
consultant (West Yost) presented five
diversion options to Central San staff.
Central San 's Engineering and Operations
staff worked with DSRSD staff to narrow
these options to two gravity diversion
options .
1
DIVERSION ALTERNATIVE 4
Would use the existing
MH -- T-4-
gravity
intortie between 2v
18"FotMan M ---
Central San7sand D R D s MssH
collection systems. `��w'N
14"Force Main PUMP STATION
w
Would divert - 1 .3 MGD of Force Main
d
Surge
18"Force Main Tank
29"Force Main
the "'2 .5 MGD average dry New ` Hlgh Busting 18'Plug
weather wastewater flow Manhole Ids/ Valve
DSRSD
MN
----------------------throu h the San Ramon
-
Pump Station .
Would start at 1 month of Figure?
Dublin San Raman Services District
Larwin Pump Station Diversion Alternatives
diversion to coincide with __43/2017 ALTERNATIVES SCHEMATIC
DERWA's peak summer
irrigation demand and grow
from there.
NA.qrr.h 1 qnj non n Pnrkot- P;inp I r�k nf 99r; 000�--= l
DIVERSION ALTERNATIVE 2
Would involve closing the
influent gate to the San M; --
Ramon Pump Station . MH
Would utilize the existing M
gravity intertie between Gl�
18"Force ,v
Main •P� S
cim I fb to
Central San's and '2
14"For..Man LARWIN
PUMP STATION °'0
ro
DSRSD's collection 12m Force'Rain ❑
systems. 24"Fonm Main 18"Force Main
Surge
Tank
Would divert all of the -2 .5
million gallons per day ----------------------IlS-Sewer -- Ml -�
(MGD) average dry Figures
Du61in San Raman Services District
weather wastewater flow 10/17/2017 Larwin Pump n Diversion AlternativesALTERNATINATI VE 2 SCHEMATIC
through the San Ramon
Pump Station .
-- 1
DIVERSION PROS
Would expand use of recycled water for a
portion of Central San 's service area (in
EBMUD's service area)
Would support one of the goals of Central
San 's Strategic Plan
Augment the Region's water supply
Explore partnering opportunities
1
DIVERSION CONS
Concerns by City of San Ramon and local
residents
Would increase the risk of overflows (due to
reduced wastewater flows) adjacent to a creek
Would increase the potential for odors
Would increase the potential for solids deposition
in Central San's collection system
Would increase the potential for corrosion , which
could damage Central San 's infrastructure
1
DIVERSION : ONS - CONTINUF
Would impact the City of Concord 's billing (flow-
proportioned )
Has potential long-term service area implications
DERWA continues connecting new recycled water
demand , making it nearly impossible to sever its
reliance on Central San's wastewater
Would support only seasonal use of Central San's
wastewater (vs. year-round )
Would reduce the availability of wastewater for
industrial (year-round demand ) recycled water
projects at Central San's main treatment plant
1
QUESTIONS
BOARD I
� 'Amlrlr v�—.'"March 1, 2018 Regular Board Meeting Agenda - Pqnp I R1 nf 99r; d04. -�- 1