Biosolids Facility SummarySummary of Biosolids Building
City of Otsego, MN P05409-2017-003
Memorandum: Biosolids Building Progress Update
Otsego East WWTF Biosolids Building
To: Otsego City Council and Staff
From: Scott Schaefer, PE
AE2S
Date: May 23, 2019
1 SUMMARY
The purpose of this memo is to provide some background information ahead of the May 28, 2019
Special Council Meeting. Additional detail will be presented with further discussion at the
meeting.
The project team has continued to refine the layout concepts of the Biosolids Building for the East
WWTF. The process layout has been solidified, and the building elements have been arranged
around the core biosolids processes of the building. The building structure has been developed
based upon the full projected biosolids capacity at full development of the City of Otsego. This
Biosolids Building will dewater and stabilize all waste solids from both the East WWTF and the
West WWTF The following characteristics are included:
• Biosolids processing and handling equipment/facilities with full redundancy
o Centrifuges are recommended; capital costs were very close between centrifuges
and screw presses; centrifuges have slightly better performance and smaller
footprint
o Chemical stabilization equipment approach was updated to two trains at buildout
instead of three due to economy of scale of the larger units
o Half installed now (1 duty plus 1 redundant; 3 duty plus 1 redundant at buildout)
o Full stabilized biosolids loadout garage
o Associated ancillary chemical systems (lime silos, polymer dosing equipment)
• Truck bay for interior unloading of West WWTF thickened waste stream (TWAS)
• Centrate and TWAS storage tanks and pumping
• Storage and maintenance garage
• Locker room with showers
• Break room / office-controls space
• SCADA (controls) upgrades
Summary of Biosolids Building
City of Otsego, MN P05409-2017-003
• Odor control (Biosolids Building and equipment replacement at Pretreatment)
• Electrical/HVAC/Plumbing
• Civil/site work
2 BIOSOLIDS DISPOSAL
Long term disposal will be at the Elk River Landfill (Waste Management) with an option for
disposal at the Vonco Landfill in Becker. The team has been in contact with both landfills to
determine pre-disposal requirements.
The stabilized Biosolids can also be beneficially used as an agricultural fertilizer supplement, and
the selected process provides a Class A designation with a likely designation of Class A,
Exceptional Quality (Class A, EQ). The Class A, EQ designation allows land spreading and/or
field stockpiling outside of the typical late fall land application window, which has been one of
the constraints of the current Class B land application program. The Class A designation also opens
up additional agricultural land that did not meet the requirements for Class B land application. No
biosolids storage is planned for the East WWTF site, but the Biosolids Building is currently
configured to allow truck hauling to opportunistically use land application while appropriate
agricultural land is still available within reasonable haul distances. This near term land application
is intended to reduce near term costs of trucking and landfill tipping fees while retaining the
reliability of landfill disposal during years with poor weather or during the growing and winter
seasons.
3 NOTABLE ARCHITECTURAL FEATURES
Several design concepts and building framing options were examined, and a practical building
structure to fit the functionality of the Biosolids Building is being recommended. The following
features are highlighted:
• Flat roof structural system with minimized corners. Primarily precast construction for
construction efficiency while allowing for finish choices.
• Current building concept includes a green roof system. This is similar to typical ballasted
membrane roof in that the waterproof element is the same, the gravel (ballast) is replaced
with a modular tray system pre-planted with low maintenance species. Generally, this
green roof system will save energy on cooling costs, but for this application it would
maintain a lower summer building temperature because much of the Biosolids Building
space would not be air conditioned.
• The building also includes Kalwall translucent panels, which allow natural lighting
during the day while also being thermally efficient.
• Landscape: continuation of the site “screen” tree line around the perimeter as well as low
maintenance planting between the existing tree line to reduce mowing and a “bee lawn”
to reduce mowing to zero to two times per year for the area around the Biosolids
Building. Landscaping around the Biosolids Building is also included.
Summary of Biosolids Building
City of Otsego, MN P05409-2017-003
4 GREEN ELEMENTS
In addition to the green roof and Kalwall systems, a geothermal heating system was considered.
Unfortunately, the payback period for the geothermal was 25+ years, which makes the system
difficult to recommend. Accommodations are planned for a future reuse water system by having a
“split” water supply system in the building. All water will initially be supplied as potable water,
but a reuse system is anticipated for future installation. The reuse water system is recommended
for deferral until the Liquid Treatment Expansion project (EL1 in the Wastewater Master Plan) to
better quantify reuse water demands. A solar system was considered, but this was pre-empted by
the green roof system. Solar could be reconsidered in lieu of a green roof.
5 COST AND FUNDING
The inflation adjusted project budget is $13.9MM, and the updated opinion of project cost is
currently tracking approximately $1MM above the budgeted amount. Areas of cost increase and
potential cost mitigation measures including bid alternate approaches and/or scope adjustments
will be a focus of discussion for the May 28, 2019 Special Meeting.
DESCRIPTION
Mobilization / General Conditions $737,000
Site Work / Civil Work $862,000
Landscape Architectural $190,000
Dewatering Equipment $1,055,000
Chemical Stabilization Equipment $2,015,000
Pumps, Piping, Conveyance $478,000
Odor Control $190,000
Structural/Architectural Building System $3,751,000
Electrical/Instrumentation and Controls $1,199,000
Mechanical $795,000
SUBTOTAL 11,272,000$
Tax*$282,000
Construction Contingencies $1,127,000
CONSTRUCTION SUBTOTAL 12,681,000$
Engineering, Legal, Admin $2,254,000
TOTAL OPINION OF PROBABLE COST 14,935,000$
OPTIONS
Upgrade to Geothermal $320,000
Pretreatment Odor Control Replacement** $145,000
**Separated due to anticipated cost through Rehab/Replacement Fund.
OPINIONS OF PROBABLE PROJECT COST - BIOSOLIDS BUILDING
*Tax is estimated based upon total project; biosolids equipment is
exempted, but other materials are still taxed.
Summary of Biosolids Building
City of Otsego, MN P05409-2017-003
The project was submitted in 2018 for Clean Water State Revolving Fund (SRF) low interest loan
consideration to determine our initial project priority list (PPL) scoring. The 2018 score was 19
points, and the funding cut-off in 2018 for 2019 construction was 44 points. Discussions with the
Minnesota Pollution Control Agency (MPCA) have improved our score to 24, which is unlikely
to be in the fundable range. The state funding statutes are written around liquid stream projects
because that is what most of the statutory permitting is written around, so this biosolids project
categorically does not qualify for many of the potential points. Improving the score would likely
require adding a significant liquid stream project element to score enough points to access an SRF
loan but would increase overall costs.
6 SCHEDULE
The project schedule is staying on track for construction in 2020. Next steps are to complete the
preliminary engineering report and move into final design.
• 2019 – Final Design
• January/February 2020 – Bidding
• Operational Start-Up – Late 2020
• Substantial Completion – Spring 2021
• Final Completion – Summer 2021