OUR MISSION: To provide our customers with high-quality, efficient and reliable water, power and sewer services in a manner that values environmental and community interests and sustains the resources entrusted to our care.
525 Golden Gate Avenue, 13th Floor
San Francisco, CA 94102
T 415.554.3155
F 415.554.3161
TTY 415.554.3488
San Francisco Public Utilities Commission
Correspondence Log
June 26, 2022 through June 29, 2022
Date Received From Subject
June 26, 2022 Steve Lawrence Item 6e, Report re Public Health Goal June 28, 2022 Peter Drekmeier TRT Letter Re: LTVA Analysis June 29, 2022 Eileen Boken A glass of ocean water: Quebec company wins award for desalination
technology
From: Steve Lawrence
To: Commission
Cc: [email protected]; [email protected]
Subject: item 6e, Report re Public Health Goal
Date: Sunday, June 26, 2022 8:54:24 AM
CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
Hon. Commissioners:
Please clarify. The report says, "This
contaminant [bromate] was
detected
in
the
treated
water
from
Harry
Tracy
Water
Treatment
Plant (HTWTP),
with
a
maximum
running
annual
average
value
of 2.1
ppb
for the
reporting period, above the
PHG
of 0.1
ppb. The detected
levels are typically
well
below
the
drinking
water
standard
of
10 ppb." The PHG is defined in the report as "a PHG
is
the
level
of a
contaminant
in
drinking
water
that
does
not
pose
a significant
risk
to
health."
Why would the drinking water standard be one hundred times the level (presumably the top level) that does not pose a significant risk to health? That makes no sense and deserves an explanation so that the public can understand whether or not bromate is a concern. Our water's bromate is at 2.1, twenty times the level of no concern, yet one-fifth the drinking water max. Bromate is a probable cause of cancer. Drinking water is one source of bromate among others.
From the cited state report: "In order to protect the entire population from carcinogenic risk from exposure to bromate in drinking water, the above estimated health-protective concentration of 0.1 ppb
(rounded to one significant figure), is utilized as the PHG for bromate in drinking water." "OEHHA selects the de minimis cancer risk value of 0.1 ppb over the noncancer value of
50 ppb for the PHG as a matter of public health prudence, to protect against all health
risks." (Bromate in Drinking Water, California Public Health Goal.) And from the "Other Regulatory Standards" section: "The U.S. EPA MCLG for bromate in drinking water is set at zero, based on
carcinogenicity. The MCL is set at 10 ppb, based on the PQL (U.S. EPA, 1998). Bromate was listed on May 31, 2002, as a chemical known to the State of California to
cause cancer under Proposition 65...."
(OEHHA=Office of Environmental Health Hazard
Assessment.)
Thank you, Steve Lawrence
PS Due to technical deficiency I am unable to participate in your online meetings
OFFICES
San Francisco
Modesto
Sonora
Mailing Address
P.O. Box 3727
Sonora, CA 95370
Phone
(415) 882-7252
Website
www.tuolumne.org
BOARD MEMBERS
John Kreiter, Chair
Harrison “Hap” Dunning,
Vice Chair
Cindy Charles, Treasurer
Kerstyn Crumb, Secretary
Eric Heitz,
Chair Emeritus
Jose Borroel
Eddie Corwin
Bob Hackamack
Camille King
Marty McDonnell
Homero Mejia
John Nimmons
Eric Riemer
Marek Robinson
Bart Westcott
June 28, 2022
President Anson Moran and Commissioners
SFPUC
525 Golden Gate Ave.
San Francisco, CA 94102
Via Email
Dear President Moran and Commissioners:
As we have mentioned before, the SFPUC’s Long-Term Vulnerability Assessment (LTVA) conveys a lot of positive news regarding future water supply in the era of climate change. For example, the report states:
According to climate projections and expert elicitations, there is a central tendency of warming of +2°C and +4°C by 2040 and 2070 (Representative Concentration Pathway [RCP] 8.5), respectively, with no clear direction of change in mean annual precipitation over the planning horizon. 1 While the LTVA is a robust scientific study, it is vague at answering questions that will help you deliberate on the practicality of the Design Drought. We have been working to get answers for you. For eight months we have been making three primary information requests of SFPUC staff:
1) How might climate change impact the SFPUC’s water supply at current demand and with the Bay Delta Plan instream flow requirements in place?
2) What is the return period (likelihood of occurrence) for the Design Drought?
3) How will earlier runoff (as predicted by the LTVA) affect the SFPUC’s water entitlements?
SFPUC staff have not been forthcoming with answers to our questions, but we continue to make progress just the same. Following are some of our findings.
Impact of the Bay Delta Plan on Water Supply
The LTVA states:
Climate change is not the single most important driver of vulnerability for the RWS. Under current RWS infrastructure conditions, either state-amended
1 Long-Term Vulnerability Assessment, p. xxii.
2 WQCP for additional IFR on the Tuolumne River or an increase in demand by 15% have significant impacts on the RWS performance that are equivalent to a decrease in mean annual precipitation of around 15%.
2 In other words, the Bay Delta Plan instream flow requirement (IFR) is equivalent to a 15% increase in water demand or a 15% decrease in precipitation.
The baseline demand used in the LTVA (227 mgd) is 16% greater than actual current demand (195 mgd). The implication is that by replacing the inflated 227 mgd demand with the IFR, we can assume that conclusions from the LTVA graphs that are based on 227 mgd demand can be applied to represent current demand and include the IFR.
The graph below suggests that under current demand and including the Bay Delta Plan IFR, the SFPUC is projected to have no less than two years-worth of water in storage at any given time over the next half century.
Source: LTVA, Figure 5-26, p. 176
The graph below suggests that under current demand and including the Bay Delta Plan IFR, the SFPUC’s delivery reliability would be 95% (assuming no change in mean rainfall, as projected in the LTVA), exceeding the 90% target.
Source: LTVA webinar, 1/27/223
2 LTVA, p. 250.
3 “Long-Term Vulnerability Assessment of San Francisco Regional Water System,” Alexis Dufour (SFPUC) and Casey Brown (UMass), January 27, 2022.
3 Return Period for the Design Drought
The following table was included in a document presented by the researchers who produced the LTVA on December 8, 2020. It shows predicted return periods for historic droughts and the Design Drought. At the time, a drought as severe as the Design Drought was projected to occur once in 25,293 years (see Return Period – Deficit).
Source: “Hydrological Drought Frequency Analysis for the Upper Tuolumne River,” 12/8/2020
The LTVA reduced the return periods for the known droughts, so we assume the return period for the Design Drought was reduced as well. We asked for an updated table, and received the following response:
As discussed in our attached Memo to File, provided to you with this December 8 presentation, the study team determined that there were insufficient data points to provide a valid scientific analysis of the return period of the Design Drought, and its sensitivity to climate change. Despite additional work to try and correct for the limited data, the return period of the Design Drought was dropped from analysis, thus no further refinement, validation, or scientific analysis was undertaken.
4 It is true, the LTVA acknowledged that the hydrologic model used to produce the LTVA overestimated flow in known dry years. It states:
4 Letter from Dennis Herrera, General Manager of the SFPUC, to Peter Drekmeier and Dave Warner at TRT, June 15, 2022.
4 The hydrologic model used to simulate the streamflow on the Tuolumne watershed in response to precipitation and temperature overestimates streamflow during dry years. For example, the flow computed at the Tuolumne River at La Grange is overestimated, and therefore WAC [Water Available to the City] is also overestimated by about 482,000 acre- feet during the drought sequence 1987-1992 (observed is 813,000 acre-feet versus simulated is 1,295,000 acre-feet).
5 In other words, observed flow was 63% of simulated flow.
In response to this observed discrepancy, the return periods for the historic droughts were updated in the LTVA, but an update of the return period for the Design Drought was omitted.
Table 5-1 in the LTVA shows that with 0% change in precipitation and +2 degrees C increase in temperature (the median projection in the LTVA
6), the revised return period for the 1976-77
drought (at 269 TAF demand: 240 mgd) is 105 years. The revised return period for the 1987-92 drought (again at 240 mgd demand) is 495 years.
Source: LTVA, p. 157
TRT produced the table below comparing return periods from the 2020 document with those in Table 5-1 of the LTVA. The combined return periods for the 1976/77 and 1987-92 droughts in Table 5-1 are 36% of the combined return periods from the 2020 report. (As an aside, we are curious why this percentage is so much lower than the 63% difference between observed and simulated flow cited above.)
5 LTVA, p. 59.
6 “By 2040, the median projections of +2°C warming combined with 0% change in mean annual precipitation results in no significant change in mean annual WAC volume…,” LTVA, p. 156.
5 We then applied 36% to the return period for the Design Drought from the 2020 document (25,293 years) and came up with an adjusted return period of 9,105 years.
Differences in Return Periods (Deficits) Between the 2020 Report and the LTVA
*Estimated return period of the Design Drought based on 36% of 2020 figure.
Source: Tuolumne River Trust
To carry the analysis further, the “Memo to File” expressed concern about the large amount of uncertainty in the analysis. To mitigate this concern, we applied 36% to the lower bounds of the 95% confidence interval for the Design Drought return period and came up with an adjusted lower bounds of the Design Drought return period of 3,277 years.
Based on the above methodology, this means one can have 95% confidence that the return period for a drought as severe as the Design Drought would be at least 3,277 years. To put this length of time in perspective, 3,000 years ago humankind was entering the Iron Age.
Both the 2020 report and Table 5-1 used 269 TAF (240 mgd) to represent demand. 240 mgd is 23% greater than current demand of 195 mgd. Using current demand would make the return period for the Design Drought quite a bit longer. It should be noted that the 240 mgd demand used in the 2020 report and in Table 5-1 is greater than the 236 mgd demand for the RWS service area projected for 2045 in the SFPUC’s Urban Water Management Plan, and staff has acknowledged that the figures included in the UWMP are more of an “outside envelope” than actual demand projections.
The implication of a 3,000 year return period (or longer, depending on demand) for a drought planning model is that making economic and environmental trade offs to plan for such a rare event is not justified.
Impact of Earlier Runoff on Water Supply
The LTVA found that runoff is expected to come earlier in the season as a result of a diminished snowpack and more precipitation arriving as rain instead of snow. It states:
6 Therefore, an increase in temperature would result in less snowpack accumulation during winter season, as more precipitation will fall as rain rather than snow, leading to 1) a reduced spring runoff volume and magnitude and 2) an increase in winter flows. The spring runoff is also expected to occur earlier in the season (Figure 5-2). 7 And:
A +2°C warming leads to a spring runoff arrival 10 days prior to the baseline temperature conditions. Median of projections estimate warming around +2°C by 2040 with most projections and elicitations between +1°C and +4°C. At +4°C, the shift in timing would be closer to 20 days prior to baseline conditions. By 2070 RCP8.5, warming could reach around +4°C with most projections and elicitations between +3°C and +6°C. 8 Our analysis of historic data suggests that if the two droughts that make up the Design Drought were to repeat, but runoff came three weeks earlier, the SFPUC would pick up an additional 237 thousand acre-feet of water – enough to add more than a year’s-worth of water to SFPUC storage. This is because the Modesto and Turlock Irrigation Districts are entitled to the first 2,400 cubic feet per second (cfs) of runoff for most of the year. But between mid-April and mid- June (time of peak runoff), the Irrigation Districts are entitled to the first 4,000 cfs of runoff.
Runoff between 2,400 and 4,000 cfs that shifts from mid-April-to-mid-June into the earlier season is water the SFPUC would pick up. Runoff between 2,400 and 4,000 cfs that shifts from post-mid-June into the mid-April-to-mid-June period is water the Irrigation Districts would pick up.
Using historic data, we produced the following table showing the impact on WAC (in thousand acre-feet) had runoff come three weeks earlier during the two droughts that make up the Design Drought. For example, had runoff been the same in 1976, but had arrived three weeks earlier, the SFPUC would have picked up an additional 20 thousand acre-feet.
Source: Tuolumne River Trust
7 LTVA, p. 147
8 LTVA, p. 147
7 SFPUC staff have claimed that the shift in runoff will not have a significant impact on the SFPUC’s water entitlements. However, it appears they only looked at the average. You will see from the following scatter plot that in dry years (like those making up the Design Drought) the SFPUC’s water entitlements improve. In wet years they decrease, but in most of those years the reservoirs are full and water has to be spilled, so it doesn’t really matter.
Each dot on the scatter plot represents one year over the past 42 years. For each year, we looked at the historic data and calculated whether a three-week shift in runoff would have increased or decreased “Water Available to the City” (WAC).
The horizontal axis represents historic WAC for each year, moving from dry years on the left to wet years on the right. The vertical axis represents the shift in WAC had runoff been the same for each year, but had arrived three weeks earlier. The zero line on the vertical axis represents no change in WAC. Dots above the zero line represent years in which WAC would have improved had runoff come earlier. Dots below the zero line represent years when WAC would have decreased had runoff come earlier.
The graph shows that in dry years, the shift in runoff almost always improves WAC, while the opposite occurs in wet years.
Source: Tuolumne River Trust
8 The implication is that during dry years the SFPUC’s unique water rights on the Tuolumne are favorably impacted by earlier runoff due to increasing temperatures and should be incorporated into planning models.
SFPUC staff claim there are other factors involved in the relationship between earlier runoff and WAC, which might be the case, but they have failed to provide any data or analysis.
Conclusion
If the SFPUC were to use reasonable demand projections, remove one year from the Design Drought (a prudent decision given the extreme return period), and consider the increase in “Water Available to the City” as a result of earlier runoff, it would significantly change the risk analysis. The following table is based on 200 mgd demand, includes the Bay Delta Plan instream flow requirement, and incorporates the additional water available to the SFPUC as a result of earlier runoff.
Source: Tuolumne River Trust
9 The results shown in the above table are beyond encouraging. Within the planning exercise that the Design Drought actually is, the SFPUC could manage a 7.5-year Design Drought and still retain positive storage with the Bay Delta Plan in affect, without developing any new alternative water supplies. The SFPUC could maintain positive storage over an 8-year Design Drought by developing 4,000 acre feet (3.8 mgd) of alternative water supplies.
Thank you for the opportunity to share our analysis of the LTVA. We look forward to working with you to implement decisions that will benefit the Tuolumne River and Bay-Delta ecosystems while also protecting the SFPUC’s water supply.
Sincerely,
Peter Drekmeier Dave Warner
Policy Director TRT Volunteer
Cc: BAWSCA
From: aeboken
To: aeboken
Subject: A glass of ocean water: Quebec company wins award for desalination technology Date: Wednesday, June 29, 2022 1:30:33 PM
CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you recognize the sender and know the content is safe.
Article from The Weather Network.
Quote from article:
"Both the Canadian government and the U.S. Department of Defense are currently exploring opportunities with Oneka Technologies, for various uses including emergency and disaster relief."
https://news.yahoo.com/glass-ocean-water-quebec-company-174313332.html Sent from my Verizon, Samsung Galaxy smartphone
OUR MISSION: To provide our customers with high-quality, efficient and reliable water, power and sewer services in a manner that values environmental and community interests and sustains the resources entrusted to our care.
525 Golden Gate Avenue, 13th Floor
San Francisco, CA 94102
T 415.554.3155
F 415.554.3161
TTY 415.554.3488
San Francisco Public Utilities Commission
Correspondence Log
July 5, 2022 through July 5, 2022
Date Received From Subject
July 5, 2022 Dennis Herrera Letters of June 21 and 28, 2022 from Tuolumne River Trust
OUR MISSION: To provide our customers with high-quality, efficient and reliable water, power and sewer services in a manner that values environmental and community interests and sustains the resources entrusted to our care.
525 Golden Gate Avenue, 13th Floor
San Francisco, CA 94102
T 415.554.3155
F 415.554.3161
TTY 415.554.3488
Jul
y 5, 2022
Mr
. Peter Drekmeier, Policy Director
Mr. Dave Warner, Volunteer
Tuolumne River Trust
P.O. Box 3727
Sonora, CA 95370
R
E: Letters of June 21 and 28, 2022 from Tuolumne River Trust D
ear Mr. Drekmeier and Mr. Warner:
T
hank you for your letters of June 21 and 28, 2022 regarding the Tuolumne River Trust’s statements and questions related to the SFPUC’s Long-Term Vulnerability Assessment.
W
e will share your questions and inquiries with the Bay Area Water Stewards agenda subcommittee as part of our agenda development discussions. We look forward to meetings where discussions address areas of interest for all attendees.
W
e thank you for your inquiry and look forward to continued productive BAWS meetings in the coming months. Please let us know if you have any additional questions by contacting Alison Kastama at [email protected].
S
eparately, we will be responding to Mr. Drekmeier’s Water Supply Scenario Request of June 30, 2022.
S
incerely,
D
ennis J. Herrera
General Manager
A
ttachment
cc:
San Francisco Public Utilities Commission
Nicole Sandkulla, CEO/General Manager, BAWSCA
Steven R. Ritchie, Assistant General Manager, Water, SFPUC Ellen Levin, Water Enterprise Deputy Manager, SFPUC
Bay Area Water Stewards participants