5.a) Anderson-Erickson Sewage Treatment System Monitoring Report (Gravel) and Continenza Application for Variance and Lot Line Adjustment � � ��
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Memo - �
To: Mayor and City Council
From: Anne Hurlburt,City Administrator
Date: September 4,2012 for September 11,2012 Work Session Meeting
Re: Anderson/Erickson Sewage Treatment System Monitoring Report and
Continenza Application for Variance and Lot Line Adjustment
The Council will receive the City Engineer's report(attached)at the September 11 Work Session.
After you have reviewed this report,you will be asked by the Continenzas to act upon their Variance
application,which includes a request for two connections to the Anderson/Erickson system: one for
the proposed new home(Lots 9 and 10,Anderson's Big Lake 2"d Addition)and one for the existing
home(Lot 8),which would have its sewer system removed as a result of the proposed new
construction on Lots 9 and 10.
There appear to be several options:
1. Allow no new connections to the sewer system. Continue monitoring as recommended by the
City Engineer.
2. Allow both homes to connect to the system. Connection fees would be as provided by the
current ordinance($4,250 per unit.) This option would involve some risk that flows and/or
loading would exceed the capacity of the system. This may also raise equity issues as other
homes adjacent to the system may not be able to hook up.
3. Allow only one home,the existing cabin on Lot 8,to hook up to the system. The status of the
existing sewage treatrnent system is unknown,and there appears to be no location on the lot to
replace it if it is removed due to the construction on Lots 9 and 10. There is a location for an
individual sewage treatrnent system on Lots 9 and 10, even though it is not the most desirable
option to the property owners. A connecrion for this one small home would pose less risk.
4. The Council could refer the report to the City's Wastewater Advisory Committee for a
recommendation before making a decision. They have a meeting scheduled for Thursday,
September 20.
If direction is given by the Council at the September I 1 meeting, staffwill prepare appropriate
resolution(s)to bring the matter of the variance request to a close at a future Council meeting
(tentatively, October 16.)
Attachments:
• Memo Dated August 28,2012 from Phil Gravel,PE—Anderson/Erickson Sewage Treatment
System,Update on Flow Monitoring and Monitoring Well Sampling Information
Stantec Consulting Services Inc.
��� �"� 2335 Highway 36 West
St. Paul MN 55113
, � TeL (651)636-4600
Fax:(651)63&1311
_ ___
Stantec
August 28, 2012
Mrs.Anne Hurlburt,Administrator
City of Scandia
14727 209th Street N
Scandia, MN 55073
Re: Anderson/Erickson Sewage Treatment System (201 Collector System)
Update on Flow Monitoring and Monitoring Well Sampling Information
Our Project No.: 193802153
Dear Anne:
A Condition and Capacity Assessment Report for the Anderson/Erickson System was presented in March of
this year. Based on the report and Council discussions regarding the report, several system repairs have
been completed and several process improvements have been implemented.
The City has been closely monitoring the flows from the system for the past four months. The City has also
completed monitoring well sampling and testing as well as sampling of some nearby drinking water wells.
This monitoring and testing information can be used to better evaluate how the system is functioning. The
following paragraphs present an update of the information received to date and an analysis of our findings
based on the information.
MONITORING WELL AND GROUNDWATER INFORMATION
The treatment system includes 4 sets of nested monitoring wells and shallow piezometers along with one
additional shallow piezometer. The wells and piezometers are used to monitor the performance of the
system. The wells and piezometers are useful in monitoring groundwater quality (i.e. nitrate nitrogen levels),
determining groundwater flow direction,and detecting if there is"mounding"beneath the system.
The attached Tables 1 and 2 show the results of well measurement and sampling over the past 5 months.
One round of sampling was completed in March 2012. A second round of sampling was completed in July
2012. The March 2012 sampling exhibited high chloride concentrations and nitrate concentrations above the
drinking water standard. The July 2012 sampling showed high chloride levels,but the nitrate levels were
below drinking water standards. Given the inconsistent groundwater quality results, additional sampling
seems prudent.
SYSTEM FLOW INFORMATION
The treatment system was installed in 1987. There have been several reports and studies over the past 10
years that have evaluated the design capacity of the system and possible methods of system expansion. The
current system Operating Permit with Washington County lists a system design flow of 6,700 gallons, a target
peak flow of 8600 gallons and a target average flow of 5300 gallons.
Flow measurement data available prior to last spring is unreliable due to issues with effluent back draining
into the lift station. Improvements to the flow measuring capabilities on the system were made last April and
the flow information since that time appears to be more accurate.
A table of ineasured flows for the last four months is attached (Table 3). Daily flows over the past few months
have ranged from 1,410 gallons to 7,622 gallons. The high 7-day rolling average was 4,958 gallons.
�n�
August 28,2012
Anne Hurlburt,City Administrator
Page 2 of 2
ANALYSIS AND RECOMMENDATIONS
The available monitoring well information is limited. Only two samples have been analyzed this year. While
the most recent round of sampling produced encouraging results,the fact remains that we have one round of
sampling that showed elevated levels of nitrates and one round of sampling that showed acceptable levels of
nitrates.
Flow monitoring over the last four months indicate that the flows are trending near the top of the permitted
range but under limits. However,the flow information is based on only a short period of time. Additional
sewer connections would add approximately 200 gallons per day per connection for an average two bedroom
home. Larger dwellings could add up to an average of 350 gallons per day.
It this time, we have the following recommendations regarding the AndersoNErickson Sewage Treatment
System:
• Since there is a limited amount of monitoring data available (especially well sampling data), a
conservative approach would be to not allow additional connections to the system until more data is
available. Additional connections could be considered ne�spring if an additional two rounds of well
sampling show acceptable results and ff flow levels continue to be under the permit target levels with
a factor of safety.
• Continue daily flow monitoring up to winter and again in the spring.
• Complete a round of well sampling this fall and plan on at least three rounds of sampling in 2013.
• Continue to take steps to complete the system repair/maintenance recommendations included in the
March 2012 Condition and Capacity Assessment Report. Consult with the new system operator to
see if they have recommended maintenance improvements.
• Continue to work with Washington County and the MPCA on system monitoring and compliance
issues. Note that the County permit requires that they approve any new connections to the system.
• Evaluate the current hook-up fee and ongoing charges for the 201 Systems to determine the fees
needed to support the system operation and maintenance for the long-term.
As presented in the March 2012 report,the Anderson/Erickson system will undoubtedly require some
treatment system improvements in the near future. Once additional flow and well monitoring data is available,
we will present specific system expansion recommendations to meet the anticipated long-term needs of the
Anderson/Erickson service area.
Please contact Clint Jordahl or me if you have any questions or require any additional information.
Sincerely,
STAN7EC
I �`"'1 r�
Phil Gravel, PE
cc: Tim Kieffer, Public Works
Sherri Buss, Planning
Attachments: Tables 1-3
Table 1
Groundwater Field Data Summary
Anderson/Erickson System
Stantec Project 193802153
MDH Top of Depth to
Well Unique Well Well Riser Groundwater Groundwater Conductivtty
Identifier Number De ha Elevation Date from TOR Elevation mho cm H Tem .°C
3/22/12 47.96 938.57 1,966 7.21 9.87
A-Deep 938453 59" 986.53 7/17/12 48.22° 938.31 -- -- --
7/26/12 48.12 938.41 1,030 7,30 11.63
3R2/12 Dry -- -- -- --
A-Shallow 421449 13.9 986.69 7J17/12 Dry° -- - - _.
7T16/12 Dry -- -- -- --
3/22/12 4b.99 939.41 2,448 6.92 10.30
B-Deep 438454 57.5° 986.40 7/17/12 47.24 d 939.16 -- -- --
7/26/12 47.17 939.23 1,569 7.14 12.06
3/22/12 11.22 975.98 -- -- --
B-Shallow 421450 14.1 987.20 7/17/12 Dry° -- -- -- --
7/26/12 12.95 974.25 -- -- --
3J22/12 51.95` 937.83 637 7.24 10.57
C-Deep 436455 57.9 989.78 7J17/12 51.85" 937.93 -- -- --
7/26/12 51.74 938.09 449 7.34 14.24
3J22/12 Dry -- -- -- --
GShallow 404748 14.2 990.40 7/17/12 Dry" -- -- -- --
7/26/1Z Dry -- -- - -
3/22/12 51.42` 937.65 1,987 7.14 10.64
D-Deep 438452 62.4 989.07 7/17/12 51.58° 937.49 -- -- -
7J26J12 51.28 937.79 1,187 7,15 11.42
3/22/12 Dry -- - -- --
D-Shaliow 404749 14.0 988.60 7/17J32 Dry° -- - ._ __
7/26/12 Dry -- -- -- --
3/22/12 Dry -- -- -- --
E-Shallow 404750 15,5 990.42 7/17/12 Dry° -- -- -- --
7/26/12 Dry -- -- - --
a-Measured from top of riser unless otherwlse indicated
b-Pump stuck in well,depth From construction records and dces not indude riser stfckup
c-Pump removed to measure water level,full recharge not verified priw to recording water level
d-7J37/12 groundwater measurements provided by Naturel Systems Utilides,MN LLC(EcoCheck)
Table 2
Groundwater Analytical Results
Anderson/Erickson System
Stantec Project 193802153
(all values reported as mg/L)
Total Kjeldahl
Well Nitrate Plus Nitrite Chloride Ammonia Nitrogen Nib�ogen
Identifiel Date NO+N d' NH
3/22/12 16.2 377 <0.04 <1
A-Deep 7/26/12 1.6 237 <p.04 <1
3/22/12 19.6 493 <0.04 <1
B-Deep 7/26/12 1.3 426 <0.04 <1
3/22/12 1.4 7.7 <0.04 <1
C-Deep 7/26/12 0.46 4.3 <0.04 <1
3/22/12 12.9 415 <0.04 <1
D-Deep 7/26/12 0.73 327 <0.04 <1
< Parameter not detec[ed at a concenVation greater than or equal to the reporting Iimit indicated
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