DDW-2024-005955

AUGUST 7,2023
Chris Wright
North Fork SSD
RR3 PO Box B1 Sundance
Provo,UT 84604
Subject:MPA Result Notification,Stewart Cascade Spring West Lateral (WS002);
North Fork SSD,System #25109,File #12826
Dear Chris Wright:
The Division of Drinking Water (the Division)issued Plan Approval for two new spring collection
laterals for Stewart Cascade Spring (identified as WS002 in the Division’s database.)As part of
the approval,the Division required that a Microscopic Particulate Analysis (MPA)be performed
on each lateral to determine whether they were under the direct influence of surface water (UDI).
Therefore,an initial Microscopic Particulate Analysis (MPA)sample was collected from the new
west lateral of Stewart Cascade Spring (WS002)on June 22,2023.The sample came back with a
score of 1,which indicates a low risk for being UDI.On this basis,the new west lateral of
Stewart Cascade Spring (WS002)is not considered to be UDI at this time.
The Division can re-evaluate this source at any time if there are circumstances that affect its
susceptibility to surface water influence.For information about UDI and MPA sampling,see the
attached UDI Definition and Possible Causes.
If you wish to begin using the new west lateral of Stewart Cascade Spring for drinking water,
please contact Cameron Draney at [phone] or [e-mail] to request the west
lateral be set up as a separate source in our database and to confirm the steps required to activate
this source.
If you have any questions regarding this letter,please contact Sarah Page at [phone] or
Brian Pattee at [phone].
195 North 1950 West •Salt Lake City,UT
Mailing Address:P.O.Box 144830 •Salt Lake City,UT 84114-4830
Telephone [phone] •Fax [phone] •T.D.D.[phone]
www.deq.utah.gov
Printed on 100%recycled paper
Chris Wright
Page 2 of 3
August 7,2023
Sincerely,
Mark Berger
Monitoring and Standards Section Manager
Enclosures:UDI Definition and Possible Causes
Laboratory Report of MPA Sample Taken on 06/22/2023
cc:Daymon Swenson,Utah County Health Department,[e-mail]
Chris Wright,North Fork SSD,[e-mail]
Division of Drinking Water VSA Team,[e-mail]
Deidre Beck,DDW Source Protection,[e-mail]
David Kruse,Division of Drinking Water,[e-mail]
Jennifer Yee,Division of Drinking Water,[e-mail]
Chris Martin,Division of Drinking Water,[e-mail]
Brent Arns,Division of Drinking Water,[e-mail]
Cameron Draney,Division of Drinking Water,[e-mail]
DDW-2023-034643
UDI Definition and Possible Causes
A groundwater source that is Under the Direct Influence of surface water (UDI)is vulnerable to
contamination by pathogens found in surface water.This vulnerability could be because the
sub-surface formation is not sufficiently filtering water as the water percolates through the
formation or because the groundwater collection infrastructure is poorly constructed and allows
surface water to directly contaminate the groundwater.The Division of Drinking Water ’s protocol
determines and classifies a groundwater source as UDI based on one or more of the following
factors:
1.Physical evidence of source deficiencies that allow,or have the potential to allow,surface
water contamination of the source
2.MPA sampling results indicating surface water influence:
a.One high-risk MPA sample result
b.Two consecutive moderate-risk MPA sample results
c.Inconclusive MPA sample results,such as alternating low-risk and moderate-risk
results,along with other water quality data or observations of the source that
indicate potential contamination by surface water
3.Water quality data indicating contamination by surface water,for example,Escherichia
coli positive source sample results not caused by physical deficiencies,detection of
Cryptosporidium or Giardia in the source water,etc.
An MPA test (Item #2)consists of running the source water through a spiral-wound filter for a
period of time.Particles collected by the filter are extracted in a laboratory,examined under a
microscope,and identified.Particles that are expected to be found only above ground or in surface
water indicate a risk of surface water contamination.Such indicators include chlorophyll-bearing
algae,parts of flying insects,plant debris,Cryptosporidium,Giardia lamblia,etc.Some of these
indicators are not pathogens,but their presence in the source water means the source water is
susceptible to contamination by pathogens found in surface water.
An MPA sample is rated as having a low,moderate,or high risk of UDI if the score is 0-9,10–19,
or 20 and above,respectively.When basing the classification of a groundwater source on MPA
results,the Division protocol classifies a source as UDI if any MPA sample is high risk or if any
two MPA samples are moderate risk or above.
The path that surface water takes as it flows to a groundwater source can and usually does vary
with season and hydrogeological conditions.It is common for the flow path to be directly
influenced by surface water under some conditions,such as during a high surface runoff during
spring,but not to be directly influenced under others.So a surface-water-influenced water source
may have MPA sample results of various risk levels,depending on the timing of the sampling.A
true groundwater source that is not under the direct influence of surface water will always have
only low-risk MPA results.