C Review Water Treatment StudyMEMORANDUM
TO:
FROM:
DATE:
SUB J:
Teresa J. Burgess, Public Works Director/City Engineer
Steve Nelson, Short Elliot Hendrickson
August 20, 2003
SEH Review of Water Treatment for the City of Chanhassen
REQUESTED ACTION
Discussion of the SEH review and recommendations.
EXECUTIVE SUMMARY:
Per Chanhassen's request, SEH has reviewed the issues and previous work done regarding the subject
of Water Quality and Water Treatment for the City of Chanhassen. After doing so, SEH believes that
a stepwise approach to implementing treatment, beginning on the east side of town and then moving
to the west side of town, is the approach best suited to Chanhassen's water system and water quality
challenges.
The stepwise approach should begin by addressing the most critical water quality objectives (i.e.,
urgent needs which if not met will lead to serious/negative consequences) and then move on to more
carefully assess appropriate means of addressing less urgent water quality issues.
The progression laid out by SEH, in tables 1 and 2, is based on the following prioritized water
quality objectives sorted from the most urgent/serious to the least.
On the east side of town:
OBJECTIVE I - meet the Minnesota Department of Health requirements;
OBJECTIVE 2 - meet the Safe Drinking Water Act requirements;
OBJECTIVE 3 - reduce colored water and taste/odor problems;
OBJECTIVE 4 - mitigate bacteriological risks in the distribution system; and
OBJECTIVE 5 - expand supply without compromising the above objectives.
On the west side of town:
OBJECTIVE 6 - assess the reliability of sequestering; and
OBJECTIVE 7 - phase in treatment as needed.
The actions SEH recommends to meet objectives on the east and west side of town are summarized in
Table 1 and Table 2, respectively. Some of the major actions and roughly approximated costs
include:
1. Implementing 3,000 gpm of pressure filtration on the east side of town to meet Objectives 1 -
4 ($4.3 - $6 million).
Page 1 of 9
2. Adding treatment at the wells to meet the toluene standard only if the standard is exceeded
after blending in the new pressure filter plant (data to date indicate this will not be needed).
3. Blocking off the lower portion of Well No. 4 if it proves necessary to reduce radium levels in
water from Well No. 4 (unit costs expected to total $30,000 - $70,000).
4. Add two Glacial Drift and one Jordan well in the Lotus Well Field ($600,000 - $1.2 million
for wells, pumps, and pittless adapters); also add the corresponding 3,000 gpm of pressure
filter treatment ($4.3 - 6 million) to meet Objective 5.
5. Assess the reliability of sequestering iron and manganese for improving water quality on the
west side of town; ($23,000 - $45,000, if sequestering for Wells 3, 7, 8, and 9 is implemented
full scale at 3 well houses. This assumes that water from Well 9 will be blended with water
from Well 3 and then a sequestering agent will be added to the combined flow.)
6. Phase in treatment as necessary on the west side of town.
DISCUSSION
Per Chanhassen's request, SEH has reviewed the issues and previous work done regarding the subject
of Water Quality and Water Treatment for the City of Chanhassen. Our thoughts regarding the best
approach for the City are summarized in the text and two tables that follow.
Chanhassen's water sy stem h as evolved with operations a nd piping designed t o accommodate t he
following two "main water supply centers":
1. East side of town -
2. West side of town -
Lotus Lake Well Field and Well 4 (by Lucy Lake)
Galpin Boulevard Well Field.
Because of this, water quality objectives can be addressed separately for each side of the city. In fact,
addressing water quality issues at each of the two "main water supply centers" will eliminate the
expensive piping and road restoration costs of bringing all the water to a central location.
Table 1 tabulates a stepwise approach to achieving the following numbered objectives through
actions on the East side of town:
On the east side of town; Lotus Lake Wells and Well 4:
OBJECTIVE 1 - meet the Minnesota Department of Health requirements;
OBJECTIVE 2 -
OBJECTIVE 3 -
OBJECTIVE 4 -
OBJECTIVE 5 -
meet the Safe Drinking Water Act requirements;
reduce colored water and taste/odor problems;
mitigate bacteriological risks in the distribution system; and
expand supply without compromising the above objectives.
Table 2 tabulates a stepwise approach to achieving the following numbered objectives through
actions on the West side of town:
On the west side of town; GalDin Boulevard Wells:
OBJECTIVE 6 - assess the reliability of sequestering; and
OBJECTIVE 7 - phase in treatment as needed.
Tables 1 and 2 also tabulate the possible consequences of not achieving each objective.
Page 2 of 9
Table 1
East Side of Town
Recommended Action
Investigate Toluene:
Perform testing requested
by the Minnesota
Department of Health.
- Lotus Lake Well Field
Objectives Met and
Things to Note
OBJECTIVE 1:
Meeting the Minnesota
Department of Health
requirements for:
Determine the source of the
toluene and assess the
location and direction of
flow of the contaminant
plume. Also test for
Toluene in the two adjacent
wells (Well 2 - which
draws water from the
Prairie Du Chien aquifer;
and Well 6 - which draws
water from the Glacial Drift
formation).
Plan to blend water from
wells with elevated toluene
levels together with water
from wells having lower
toluene levels. This would
be done in a Lotus Lake
Water Treatment Plant
(WTP).
Toluene - Blending in a
WTP would more than
address the current toluene
levels. In fact, there have
not been any well samples
with levels above 0.6 ug/L
and the toluene standard is
1.0 ug/L. The subject
sample was taken from
Well 5 which draws water
from the Glacial Drift (GD)
formation. Hopefully
toluene is contained in the
GD formation and has not
migrated down to the
deeper Prairie Du Chien -
Jordan aquifer.
Modify Well No. 4:
Block off the deeper portion
of Well No. 4 (i.e., block
off the Franconia Ironton-
Galesville aquifer).
(unit costs expected to total
$30,000 - $70,000)
OBJECTIVE 2:
Meeting the Safe Drinking
Water Act requirements for:
Radium - Deeper aquifers
have higher radium
concentrations. Blocking
off the deeper aquifer
should reduce radium levels
in water pumped from Well
No. 4.
Well No. 4 has had a 6.8
pCi/L reading and the
standard is 5.0 pCi/L.
Page 3 of 9
Consequences of not
Meeting Objective
Would, at a minimum, set a
precedent of Chanhassen
not being cooperative in
their dealings with the
Minnesota Department of
Health (MDH).
Such a precedent would
result in stricter penalties,
should the MDH ever be
required to issue a Notice of
Violation (NOV) or
Administrative Penalty
Order (APO) against
Chanhassen.
An uncooperative precedent
would also give the public
and press grounds for
"concern" should a boil
order, NOV, or APO ever
be ordered against
Chanhassen by the MDH.
If a standard is exceeded the
Minnesota Department of
Health (MDH) will take the
following actions.
NOV - (Notice of
Violation) will trigger
Public Notice. City
must verify that public
notice was sent out or
else MDH will go to
APO. Public notice
must include
description of
recognized health
Table 1
East Side of Town - Lotus Lake Well Field
Recommended Action Objectives Met and
Things to Note
Be aware that blocking off
the lower aquifer will
sacrifice some of Well 4's
pumping capacity.
Construct Filter Plant:
Construct a pressure filter
Water Treatment Plant
(WTP) at Lotus Well Field
to treat water from Wells 2,
5, and 6; a total flow of
about 3,000 gallons per
minute which is 4.32
million gallons per day
(MGD).
The WTP is estimated to
cost between $4.3 and $6
million based on a $1.0 to
$1.4 per gpd unit cost for
such facilities.
OBJECTIVE 2:
Meeting the Safe Drinking
Water Act requirements for:
Arsenic - adsorption of
arsenic onto iron floc
and subsequent co-
filtration would be
expected to reduce the
arsenic by about 80%.
Note that Well 6 has
reached the standard of
10 ug/L).
2. Radium - adsorption
onto manganese oxide
coated greensand can
reduce radium levels by
about 33%. Note that
Page 4 of 9
Consequences of not
Meeting Objective
implications of the
given constituent.
e
APO - (Administrative
Penalty Order) In which
State can set a daily
financial penalty (often
$1,000 per day) that can
be forgivable or
unforgivable. State can
also order and enforce a
cease and desist
requiring that the City
shut down its well(s) or
water treatment plants.
After NOV a City is
typically given about 3
months to let the MDH
know what will be done to
bring the system into
compliance within the next
3 years.
If a standard is exceeded the
Minnesota Department of
Health (MDH) will take the
following actions.
NOV - (Notice of
Violation) will trigger
Public Notice. City must
verify that public notice
was sent out or else
MDH will go to APO.
Public notice must
include description of
recognized health
implications of the
given constituent.
2. APO - (Administrative
Table 1
East Side of Town
Recommended Action
Lotus Lake Well Field
Objectives Met and
Things to Note
the radium standard has
not been exceeded by
these wells but the level
in Well 2 has reached
4.62 pCi/L (close to the
standard or 5 PCi/L).
Construct Filter Plant:
(as per above)
Construct Filter Plant:
(as per above)
OBJECTIVE 3:
Reduce colored water and
taste/odor problems.
Note that the average iron
and manganese levels in
Wells 2, 5, and 6 are 0.8
mg/L and 0.3 mg/L,
respectively. This is about 3
times the iron standard (0.3
rog/L) and about 7 times the
manganese standard (0.05
mg/L). These levels are too
high for sequestering.
OBJECTIVE 4:
Mitigate bacteriological
risks in the distribution
system.
Page 5 of 9
Consequences of not
Meeting Objective
Penalty Order) In which
State can set a daily
financial penalty (often
$1,000 per day) that can
be forgivable or
unforgivable. State can
also order and enforce a
cease and desist
requiring that the City
shut down its well(s) or
water treatment plants.
After NOV a City is
typically given about 3
months to let the MDH
know what will be done to
bring the system into
compliance within the next
3 years.
Iron and manganese sent
out into the distribution
system will tend to settle
out. This settled sludge can
shield bacteria from the
chlorine meant to kill them.
Bacteria such as sulfur
reducing bacteria can then
contribute to odors. This
results in a lack of
consumer satisfaction and
confidence.
Iron and manganese sludge
in the distribution system
(as per above) can shield
bacteria from the chlorine
meant to kill them. This sets
up an environment that is
more conducive to harmful
bacteria. Total Coliform
testing is required by the
Table 1
East Side of Town - Lotus Lake Well Field
Recommended Action Objectives Met and
Things to Note
Page 6 of 9
Consequences of not
Meeting Objective
MDH to check for
environments conducive to
harmful bacteria.
Per MDH requirements,
Total Coliform is tested for
monthly in Chanhassen's
distribution system. If Total
Coliform is present the
following will occur.
The City will be required to
resample and test the site of
the violation (1 sample),
sample and test one site on
each side of the violation
site (2 more samples),
sample and test a site
representative of the water
elsewhere in the system (a
4th sample). If Total
Coliform is present in any
one of these 4 samples, the
City must issue a boil order.
During a boil order the City
must make every reasonable
effort to keep people from
drinking the water. This
includes notifications by
TV, radio, and placing
posters in restaurants etc.
Once a boil order is issued
the reputation of the City
officials, council, and staff
will be on the line. The
public will dig to find what
the City did to minimize
risks of such an occurrence.
In such a situation, having a
cooperative history with the
Minnesota Department of
Table 1
East Side of Town Lotus Lake Well Field
Recommended Action Objectives Met and
Things to Note
Consequences of not
Meeting Objective
Health will be critical.
Exl~and System Cal~acitv:
Add the following wells to
the Lotus Lake Well Field
and expand the treatment
capacity of the pressure
plant from 3000 gpm to
6000 gpm.
Well 10 - 1000 gpm; Jordan
Well 11 - 1100 gpm; GD
Well 12 - 1000 gpm; Jordan
($600,000 - $1.2 million for
wells pumps and pittless
adapters)
($4.3 - $6 million for
pressure filter treatment)
Establish an 18" water main
connection between the
Lotus Lake Well Field and
the west end of town. There
is currently about 3800 feet
of 10" water main between
the Lotus Lake Well Field
and the 18" trunk main
running along West 78th
Street. Replacing the 3800
feet of 10" water main with
18" water main will cost
about $247,000 ($65/ft)
plus restoration costs.
OBJECTIVE 5
Expand supply without
compromising the above
objectives.
This will enable the City to
meet 75% of the year 2010
Maximum Day Demand
with treated water.
Designing for meeting 80%
of the Maximum Day
Demand is a financially
prudent approach being
taken by some metropolitan
communities. The idea
being that on Maximum
Days (when the seasonal
maximum 24 hour water
demand occurs) a lot of the
water goes quickly onto
people's lawns anyway;
thus, iron/manganese do not
have much time to settle out
in the distribution system.
So having 20% (or 25%)
untreated water flowing
through the distribution
system on the Maximum
Use Day does not tend to
contribute to settling or the
subsequent taste / odor /
bacteria problems.
May have difficulty finding
water on the west side of
town (unless glacial drift is
present).
Using too much untreated
could re-establish the
consequences listed above.
Page 7 of 9
Table 2
West Side of Town - Galpin Boulevard Well Field
Recommended Action Objectives Met and Consequences of not
Test Sequesterin~ Al~ents:
Conduct jar testing and
possibly full scale testing of
sequestering agents for
Wells 3, 7, 8, and future
Well 9.
($23,000 - $45,000, if
sequestering for Wells 3, 7,
8, and 9 is implemented full
scale at 3 well houses. This
assumes that water from
Well 9 will be blended with
water from Well 3 and then
a sequestering agent will be
added to the combined
flow.)
Things to Note
OBJECTIVE 6:
Assess the reliability of
sequestering.
Note that the average iron
and manganese in Wells 3,
7, and 8 is 0.14 mg/L and
0.36 mg/L, respectively.
This is under the iron
standard of 0.3 mg/L and
about 7 times the
manganese standard (0.05
mg/L). Although
manganese is quite high, the
total of iron and manganese
is low enough that
sequestering might help.
Meeting Objective
Would not know if
sequestering might help
with water quality on the
west end of town.
Phase in Treatment:
Evaluate the success which
sequestering has in
achieving Objectives 3 and
4 and phase in additional
treatment as needed. If
treatment is deemed
necessary for all wells
(Well 3, 7, 8, and 9) the
treatment capacity would
need to be about 5,500 gpm
(about 8 MGD). The cost
for the plant would be about
$11 million plus the cost of
the land and the cost to
route water main to the
plant.
Abandon the School Well:
The City should plan on
abandoning the school well
and use it as little as
possible in the interim.
OBJECTIVE 7:
Phase in treatment as
needed.
OBJECTIVE 3:
Reduce colored water and
taste/odor problems.
OBJECTIVE 4:
Mitigate bacteriological
risks in the distribution
system.
OBJECTIVE 3:
Reduce colored water and
taste/odor problems.
OBJECTIVE 4:
Consequences associated
with not meeting objectives
3 and 4 are listed above in
Table 1.
Water form the School Well
would be too difficult to
route to the Galpin Well
Field. The School Well's
iron level of 1.9 mg/L is too
high to send to the
Page 8 of 9
Table 2
West Side of Town - Galpin Boulevard Well Field
Recommended Action
Objectives Met and
Things to Note
Mitigate bacteriological
risks in the distribution
system.
Consequences of not
Meeting Objective
distribution system.
Consequences associated
with not meeting objectives
3 and 4 are listed above in
Table 1.
C~
Kelley Janes, Utility Superintendent
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