5. Bliss Drainfield Nitrate Mitigation
Staff Report
Date of Meeting: 7-21-20
To: Mayor, City council
From: Adam Hawkinson, Director of Public Works
Re: 201 Bliss Drainfield Nitrate Mitigation
Background:
The Nitrate levels at the Bliss drainfield have been high in test well 004 for as long as the MPCA
has records and became non-compliant when the MPCA reduced the level of permitted nitrates
in ground water in about 2006. The MPCA has, in the past, asked the City to come up with a
plan to address the nitrate issue. Currently our permit is in review and the Covid-19 pandemic
has slowed the MPCA process for reviewing and processing permits. In 2019 the PW
department exposed several of the dropboxes in a drainfield area to see what was occurring in
the field. It was found that the majority of the effluent waste water was going mainly into one
trench out of the ten provided in the field thus hydraulically overloading the ground in that area
and minimizing organic and filtered treatment of nitrogen. This is still occurring after the
system has been in operation for 34 years. Options to address the nitrate issue have cost
estimates of $500,000.00 to $950,000.00 which include hooking up to the forcemain of a
neighboring community or installing an on-site treatment system to perform extra treatment.
Issue:
The Director of Public Works is requesting to move forward with nitrate mitigation by
performing dropbox modifications to spread out the effluent to other trenches and to
introduce microbial treatment into Lift station #2 to begin the breakdown of nitrogen
throughout the whole system.
Proposal Details:
The PW Director has been in contact with the Minnesota Rural Water Association professionals
and with companies that produce bio-treatments for waste water systems. Together, we as a
team, have created a solid plan to reduce the nitrate issue plaguing the system.
By digging up 4 dropboxes in each drainfield and reducing the intake of the effluent into each of
the trenches, the effluent will be spread out over 4 times the area and reduce the hydraulic
loading. The goal is to lower the rate to 17 gallons per minute being added to each trench.
Included in the project would be the installation of an access to each dropbox. They would be
exposed at the surface for monitoring and so changes could be made to the inlet pipes to the
trenches in the future. Secondly, there would be an addition of bacteria that biologically break
down nitrogen as it flows through the system and will eventually create what is referred to as a
bio-mat in the trenches. This would be introduced on a weekly basis to lift station #2. The bio-
mats sustain and retain the bacteria that break down organic matter as the effluent is
introduced into the system. At this time, the first trench that receives most of the effluent
waste has a very minimal bio-mat even after 34 years of use.
Fiscal Impact:
PW has received two quotes for the excavation and changes to the upgrades to the drainfields.
Bacteria treatment is
Smilies - $6006.00
Peterson - $6,350.00
Bacteria - $1050 / year - $525.00 for the 2020 season.
There is $9,000.00 in the Misc. Contractor fund for the 201 sewer system that may be used for
this project and another $16,000.00 in the budget for mechanical repairs for the lift stations as
need for valves and pumps. This years half of the $1050.00 would come out of the operations
fund for the 201 system.
Options:
1.) Proceed with the recommendation.
2.) Don’t proceed.
Recommendation:
Option 1
Dear City of Scandia,
Over the past two months I have personally been in your city looking at ways to solve the wastewater
treatment issue you’re having. I have looked deeply into the problem and have done hours of research
by calling engineers, vendors, and contractors along with my knowledge of wastewater believe this can
be fixed.
Wastewater treatment needs to be evenly distributed amongst the system allowing effective even
treatment. However in Scandia the flow is extremely heavy and overloaded to one side of the treatment
plant. When this happens the problem is solely over saturated soils. The soils of your treatment system
eventually become too full of waste and can no longer filter efficiently.
The fix option to solve an over-saturated soil problem is to even out the flow. #1 is completely
overloaded while #4 is completely under loaded. This comes from poor installation or design and can be
corrected. From my findings what needs to happen to create the best treatment possible and longevity
to Scandia wastewater system a diffuser needs to be installed. A diffuser is a system that will slow down
flow to #1 while pushing wastewater evenly to #2, #3, .
Installing diffusers will allow the treatment plant to work to its full potential. I recommend digging up
and installing these diffusers like this #1 capping and drilling a hole in the cap to allow water through yet
building up enough pressure to push into #2. Then capping #2 and drilling a hole in the cap to allow
water through evenly and give the system enough pressure to keep moving water down the line to #3 &
#4 to evenly distribute all wastewater throughout the system.
In my opinion Scandia’s wastewater treatment plant can be fixed/ upgraded to adequately treat
wastewater thus prolonging the life of the system and saving the city money for future failure of the
treatment plant in repairs.
Thank You
Joe Janson
MRWA Wastewater Trainer/Advisor
218-513-0225
joe.janson@mrwa.com
Estimate
Date
3/16/2020
Estimate #
299
Name / Address
CITY OF SCANDIA
14727 209TH STREET N
SCANDIA, MN 55073
ATTN: ADAM
Peterson Excavating, Inc
P.O. BOX 69
SCANDIA, MN. 55073
E-mail
PETERSONEXC@YAHOO.COM
Web Site
petersonexcinc.com
Description
MACHINE & LABOR DIG 12 DROP BOXES AND CAP PIPES WITH HALF CUT CAPS $ 4,500.00
MISCELLANEOUS 24 INCH RISER PIPE 12 CONCRETE LIDS SEED AND MULCH $ 1,850.00
******* IF 24 INCH WILL NOT WORK WE WILL RE ADJUST RISERS AND LIDS WITH ADAMS APROVIL*******
Payment is due upon receipt of invoice. A finance charge of 1.5% per month (18% per year)
be added to all invoices over 30 days, in addition to any expenses incurred in collection.
This Proposal is not gauranteed after 30 days from date of submission.
Smilies Sewer Service
P.O. Box 100
Scandia, MN 55073
+1 6514333005
info@smiliessewer.com
www.smiliessewer.com
Estimate
ADDRESS
The City of Scandia
14727 209th St N
Scandia, MN 55073
ESTIMATE #1153
DATE 03/19/2020
EXPIRATION DATE 07/19/2020
ACTIVITY QTY RATE AMOUNT
Services
Dig up/ backfill 12 distribution boxes machine and labor - Repairs
to the Bliss Development treatment drainfield area
1 4,100.00 4,100.00
Material
Materials manhole riser, tar sealer, manhole covers and manhole adapter
rings. Seed and mulch
1 1,906.00 1,906.00
TOTAL $6,006.00
Accepted By Accepted Date