April 22, 2003
Mr. Donald F. DiMartino
Department of Public Works
26 Blackstone Street
Bellingham, MA 02019
Re: Water Supply Maximization Study Report
Dear Mr. DiMartino:
Dufresne-Henry is pleased to
present this report of our study on maximizing the yield from your water
supplies. The objective of this project was to determine the maximum supply
that each well can provide and present recommendations for the improvements
necessary to achieve these yields.
A summary table of the
results for each well is given below.
|
Pump Station |
Current Capacity (gpm) |
Short-term Potential
Capacity (gpm) |
Limiting Parameter |
Comments on Well and Pumps |
|
1 |
200 |
360 |
Well |
Cleaning required |
|
2 |
130 |
250 |
Wells |
Aquafreed or replacement
required |
|
3 |
450 |
450 |
None |
No improvements required |
|
4 |
260 |
360 |
Well and pump |
Cleaning required and pump
improvements |
|
5 |
100 |
200 |
Well and pump |
Aquafreed or replacement
required with pump improvements |
|
7 |
295 |
295 |
None |
No improvements required |
|
8 |
340 |
470 |
Pump |
Pump improvements |
|
11 |
150 |
250 |
Well |
Cleaning required |
|
12 |
347 |
347 |
Pump |
No improvements required |
|
|
|
|
|
|
|
TOTALS |
2272 or 3.3 MGD |
2982 or 4.3 MGD |
Wells and Pumps |
4.3 MGD is the maximum pumping capacity if all wells are cleaned and
pumps are improved. |
As presented above, the
Bellingham Water Supply system has current pumping
capabilities of 3.3 million gallons per day (MGD). However, the most conservative method of
determining maximum water supply capacity is to add up all capabilities and
then subtract out the single highest operating capacity source. In the case of Bellingham, this would result
in 2,272 gallons per minute (gpm) minus 450 gpm (Well 3) for a total of 1,822
gpm or 2.6 MGD for a current maximum
water supply capacity.
If short-term improvements
are made such as cleaning of wells as required (including Aquafreed at Wells 2
and 5) and pump improvements, the Bellingham Water Supply system has pumping capabilities of 4.3 million
gallons per day (MGD). The single
highest operating capacity source out of service would result in 2,982 gallons
per minute (gpm) minus 470 gpm (Well 8) for a total of 2,512 gpm or 3.6 MGD for a potential maximum water
supply capacity.
Furthermore, our testing
indicates that Wells 8 and 12 are capable of supplying significantly more water
that their current permit allows. If
increased yield approvals are secured from the Department of Environmental
Protection (DEP) for Wells 8 and 12, we estimate a potential capacity of 740
and 880 gpm, respectively from those wells.
If long-term improvements were made such as permit approvals for Wells 8
and 12, the pumping capabilities
would be a total of 5.4 million gallons per day (MGD). The single highest operating capacity source
out of service would result in 3,785 gpm minus 880 gpm (Well 12) for a total of
2,905 gpm or 4.2 MGD for a potential
maximum water supply capacity.
The following paragraphs
describe the findings of the field tests and our recommendations.
Well No.1
The flow test was performed on June 25, 2002. The field test pump curve was found to be generally in agreement with the design curve, meaning the pump is performing satisfactorily. Graphs of the field test pump curve compared to the design curve for all wells tested are appended. Also appended are the pump specifications from which we obtained the design curves.
The 24-hour test was
conducted at 180 gpm resulting in a specific capacity of 30 gallons per minute
per vertical foot (gpm/ft). The
drawdown stabilized quickly with about 10 feet remaining over the top of the
screen. This well typically pumps 200
gpm, which is significantly less than the DEP approved yield of 360.
The well cleaning data
indicates that the well was last cleaned in August 1993 and the specific
capacity was 49.9 gpm/ft. The specific
capacity of 30 gpm/ft obtained during the June 25, 2002 flow test was not the
maximum capabilities of this well since there was 10 feet remaining over the
top of the screen. Cleaning is required
for this well in order to reestablish a specific capacity of about 50 gpm/ft.
·
We recommend cleaning of
this well to regain an additional 160 gpm to restore the original yield of 360
gpm and 50 gpm/ft.
Well No.2
The flow tests were
performed on January 2, 2003. This
source consists of Wells 2.6.1, 2.6.2 and 2.6.3, all 6-inch wells, and 2.8.1,
an 8-inch well. The flow test could not
be completed because the amount of flow from each well was barely measurable
with the instrumentation in the field.
No 24-hour test was
conducted. This source typically pumps
130 gpm, significantly less than the 250 gpm permitted safe yield. The yield of this source appears to be
limited by the wells.
The well cleaning data
indicates that the wells were last cleaned in June 2002 and the specific
capacities were 1.8, 2.3, 2.9 and 3.3, respectively. Past well cleanings in 2000 and 1999 have yielded similar results
for specific capacity. In order to
achieve the permitted safe yield of 250 gpm, the specific capacity of each well
should average about 3.1 gpm/ft.
Alternative methods of cleaning should be considered for this source,
such as Aquafreed. If this cleaning
method is not successful then replacement wells should be considered.
·
Alternative cleaning methods
are recommended such as Aquafreed to recover the original well yield averaging
3.1 gpm/ft from this group of four wells.
·
If the Aquafreed process is
not successful then replacement wells should be constructed for 250 gpm. This work would include a pump test,
permitting, engineering and construction of the well and site piping.
Modifications to Pump
Station 3 were completed in February 2003.
Well 3.1 in no longer in use.
Improvements included construction of Well 3.3, installation of VFDs for
Wells 3.2 and 3.3 and the installation of new process piping in the pump
station. Construction of Well 3.3 was
required since the Aquafreed process performed on Well 3.2 was not successful
in restoring specific capacity to the original level of 42.5 gpm/ft.
Wells 3.2 and 3.3 were
started up on February 28, 2003. A pump
test was performed on that date. The
capacity of Well 3.3 was determined to be 450 gpm and the level of Well 3.2
stabilized at a capacity of 150 gpm.
The DEP approved yield for this pump station is 450 gpm. We do not recommend a Withdrawal Permit
Amendment from DEP for this pump station since in our judgment, a higher yield
is not sustainable. It is recommended
that this facility be operated with only Well 3.3 being pumped a majority of
the time. Well 3.2 can be used as a
backup to give Well 3.3 a periodic rest.
The pump test for Well 3.2 was conducted at 150 gpm resulting in a
specific capacity of 15.0 gpm/ft. The
pump test for Well 3.3 was conducted at 450 gpm resulting in a specific
capacity of 20.9 gpm/ft. Modifications
will be required to the Corrosion Control Facility which treats Pump Station 3
and Pump Station 4 due to the anticipated increased flow.
·
No work is required at this
time for this pump station
·
The capacity of the
Corrosion Control Facility, which serves this pump station and Pump Station 4,
should be increased to allow proper treatment of a maximum of 810 gpm (450 gpm
from Pump Station 3 and 360 gpm from Pump Station 4). The improvements would simply include an increased sized day tank
and properly sized chemical feed pumps.
Well No.4
The flow test was performed
on January 29, 2002. The VFD is
programmed so that the pump cannot run at 100% capacity (60 Hz) to eliminate
the possibility of overpumping this well.
This results in the pump curve to be shifted downward and makes it impossible
to evaluate potential wear in the pump.
The 24-hour test was
conducted on January 29, 2002 at 210 gpm resulting in a specific capacity of
11.7 gpm/ft. The drawdown stabilized
quickly with about 8 feet remaining over the top of the screen. Using a safety factor of 5 feet over the
pump intake, this well should be capable of 350 gpm, about 10 gpm less than the
DEP approved yield. Both the pump and the well capabilities therefore limit the
yield.
The well cleaning data
indicates that the well was last tested in September 1975 and the specific
capacity was 10.9 gpm/ft. An earlier
test was conducted on May 8, 1968 resulting in a specific capacity of 27.5
gpm/ft. The specific capacity of 11.7
gpm/ft obtained during the January 29, 2003 flow test was not the maximum
capabilities of this well since there was 8 feet remaining over the top of the
screen. Cleaning is required for this
well.
·
We recommend cleaning of
this well to regain an additional 10 gpm to restore the original yield of 360
gpm and 27.5 gpm/ft.
·
Additionally, we recommend
that the pump be pulled for inspection of the impellers and/or bowl assemblies
with replacement as necessary.
·
Finally, the VFD should be
reprogrammed to allow the motor to be operated up to 100 % capacity (60Hz) and
the speed of the motor should be controlled to maintain a desired level in the
well.
The flow test was performed
on January 30, 2002. The pump curve was
found to be shifted downward in relation to the design curve, meaning there is
wear in the impellers and/or the bowl assemblies.
The 24-hour test was
conducted at 140 gpm resulting in a specific capacity of 9.3 gpm/ft. The water level dropped below the data
logger transducer during the test. The
well typically pumps 100 gpm and this is likely to be approximately the current
maximum yield of this well. Both the
pump and the well capabilities therefore limit the yield. With cleaning, it maybe possible to regain
the original 200 gpm yield. Regardless,
the pump bowls will need adjustment in order to provide the pressure necessary
to deliver any increased rate into the system.
The well cleaning data
indicates that the well was last cleaned in March 1987 resulting in a specific
capacity of 14.0 gpm/ft. The specific
capacity of 9.3 gpm/ft obtained during the January 30, 2002 flow test was
greater than the current maximum output of this well since the level dropped
below the data logger transducer. In
order to achieve the permitted safe yield of 200 gpm, the specific capacity of
the well should be about 20 gpm/ft.
Since the well cleaning history for this well indicates that only 14.0
gpm/ft is achievable with routine cleaning, we recommend that alternative
cleaning be performed at this site. We
recommend that the Aquafreed process be performed to maximize the potential
from this source. The final option to
regain the safe yield of 200 gpm would be to permit and construct a replacement
well.
·
We recommend the Aquafreed
cleaning process for this well to regain an additional 100 gpm to restore the
original yield of 200 gpm and specific capacity of 20 gpm/ft.
·
If the Aquafreed process is
not successful then a replacement well should be constructed for 200 gpm. This work would include a pump test,
permitting, engineering and construction of the well and site piping.
·
Additionally, we recommend
that the pump be pulled for inspection of the impellers and/or bowl assemblies
with replacement as necessary.
Well No.7
The flow test was performed
on February 4, 2002. The pump curve was
found to match the specification curve at the design pressure. At higher pressures, the pump was performing
above the specification, which is not uncommon for quality pumps such as Gould.
The well typically pumps 285
gpm and the DEP approved yield is 295 gpm. The 24-hour test was conducted at
300 gpm resulting in a specific capacity of 11.8 gpm/ft. The drawdown stabilized with approximately 5
feet of water remaining over the top of the screen.
The well was cleaned by
A&W Artesian Well Co. beginning on March 13, 2003. The initial specific capacity was reported
to be 8.3 gpm/ft and after cleaning and redevelopment the specific capacity was
improved to 15.0 gpm/ft. When the well
is placed back in service we anticipate that a pumping rate of 295 gpm will
result in a drawdown of 20 feet leaving about 10 feet of water over the top of
the well screen.
·
No work is recommended for
this well at this time.
Well No.8
The flow test was performed
on February 5, 2002. The pump curve was
found to be shifted downward in relation to the design curve, meaning there is
wear in the impellers and/or the bowl assemblies.
The well typically pumps 340
gpm and the DEP approved yield is 470 gpm. The 24-hour test was conducted at
530 gpm resulting in a specific capacity of 31.2 gpm/ft. The drawdown stabilized with approximately
16 feet of water remaining over the top of the screen.
The well was cleaned by
A&W Artesian Well Co. beginning on March 21, 2003. The initial specific capacity was reported
to be 26.1 gpm/ft and after cleaning and redevelopment the specific capacity
was improved to 37.3 gpm/ft.
Using a safety factor of 5
feet over the top of the screen, this well should be capable of 740 gpm. At this rate, the well could not be operated
longer than 15 hours per day without exceeding the approved daily volume. The
yield of this well is therefore limited by the pump and by the DEP approved
daily volume.
Wells 7 and 8 are the source
wells for the Water Treatment Plant (WTP) located at this site. The maximum capacity of the WTP is 1,150 gpm
(4 filters at 95 ft2/filter and a loading rate of about 3 gpm/ft2). The maximum capacity of this WTP would not
be exceeded even if the approved yield of Well No.8 was increased.
·
The first priority
improvement to this well is to have the pump pulled for inspection of the
impellers and/or bowl assemblies with replacement as necessary to allow pumping
at the DEP approved rate of 470 gpm.
·
Secondly, the New Source
Approval process should be completed through the DEP Water Supply Division in
order to increase the yield of this well to 740 gpm.
Well No.11
The wells were tested
individually on June 13, 2002. This
source consists of Wells 11.1, 11.2, 11.3, 11.4 and 11.5. All the pump curves were found to be shifted
downward in relation to the design curves, meaning there is wear in the
impellers and/or the bowl assemblies.
The sum of the yields of the
five wells at this source is typically 150 gpm and the DEP approved yield is
250 gpm. No 24-hour tests were
performed, however, the maximum individual well yields are estimated at 40, 50,
50, 10, and 125 gpm for Wells 11.1 through 11.5, respectively. We recommend that Well 11.4 be abandoned due
to its relatively insignificant yield.
With VFDs for each well and new level transducers (to control the speed
of the pump in order to maintain a preset level over the pump bowl) this source
should be able to produce the DEP approved yield of 250 gpm.
The well cleaning data
indicates that the wells were last cleaned in April 2002 and the specific
capacities were 2.4, 5.5, 4.8, 1.5 and 18.0, respectively. Past well cleanings in 2000 and 1999 have
yielded slightly better results for specific capacity. In order to achieve the permitted safe yield
of 250 gpm, the specific capacity of Well 11.1, 11.2 and 11.3 should average
about 4.0 gpm/ft and the specific capacity of Well 11.5 should be about 20.0
gpm/ft. The yield of these wells can be
improved with cleaning.
·
We recommend abandoning Well
No.11-4 since the well yield is insignificant.
·
Cleaning of these wells is
recommended to regain a specific capacity of about 4.0 gpm/ft in Wells 11.1,
11.2 and 11.3 and a specific capacity of about 20.0 gpm/ft in Well 11.5.
·
Additionally, we recommend
that the pumps be pulled from Wells 11.1, 11.2 and 11.3 for inspection of the
impellers and/or bowl assemblies with replacement as necessary. We also recommend that the size of the pump
for Well 11.5 be increased to 125 gpm at the required system pressure.
·
Finally, VFDs should be
installed for the remaining four (4) wells with level transducers in each.
Well No.12
The flow test was performed
on January 31, 2002 The pump curve was found to be shifted downward in relation
to the design curve, meaning there is wear in the impellers and/or the bowl
assemblies. A new pump was installed in
September 2002 and sized to pump at the DEP approved yield of 347 gpm.
The 24-hour test was
conducted at 335 gpm resulting in a specific capacity of 41.9 gpm/ft. The drawdown stabilized with approximately
26 feet of water remaining over the top of the screen. Using a safety factor of 5 feet over the top
of the screen, this well should be capable of 880 gpm. At this rate, the well could not be operated
longer than 9 hours per day without exceeding the approved daily volume. The
yield of this well is limited by the pump and the DEP approved yield.
·
The New Source Approval
process should be completed through the DEP Water Supply Division in order to
increase the yield of this well to 880 gpm.
Conclusions and Recommendations
Several factors are limiting
the maximum available water from the Bellingham sources. These include plugged
wells, worn pumps, and DEP approved yields.
The following tables detail the work required in the short-term and the
long-term to increase capacity from the water supply wells.
Short-Term Improvements
|
Pump Station |
Proposed Improvements |
Phase 1 Estimated Cost Budget |
Phase 2 Estimated Cost Budget |
|
1 |
Well cleaning (1 well) |
$15,000 |
|
|
2 |
Aquafreed process (4
wells) |
$60,000 |
|
|
2 |
Well replacement (if
necessary) |
--------- |
$140,000 |
|
4 |
Well cleaning (1 well) |
$15,000 |
|
|
4 |
Pump improvements |
$10,000 |
|
|
5 |
Aquafreed process (1 well) |
$20,000 |
|
|
5 |
Well replacement (if
necessary) |
-------- |
$120,000 |
|
5 |
Pump improvements |
$10,000 |
|
|
8 |
Pump improvements |
$10,000 |
|
|
11 |
Well cleaning (4 wells) |
$40,000 |
|
|
11 |
Pump improvements |
$20,000 |
|
|
|
|
|
|
|
TOTAL |
|
$200,000 |
$260,000 |
If short-term improvements
are made as detailed above, the maximum water supply capacity would increase
from a current level of 2.6 MGD to a potential level of 3.6 MGD (conservatively
estimated with the highest operating capacity source offline).
Long-Term Improvements
|
Pump Station |
Proposed Improvements |
Estimated Cost Budget |
Duration |