City Council Meeting Date: June 15, 2021
To: Mayor and City Council
City Administrator
From: Justin Wagner, Utilities Manager
David Bennett, P.E., Public Works Director/City Engineer
Title
Consider Motion Adopting Wastewater Treatment Plant’s Facility Plan Update.
Body
Action Requested:
The Northfield City Council considers a Motion adopting the Wastewater Treatment Plant’s Facility Plan Update.
Summary Report:
On August 5, 2019, the City of Northfield hired Jacobs Engineering Group (Jacobs) to provide the following services as part of the contract:
1) Phase 1 - Operations Assessment, previously presented to Council and included in appendix
2) Phase 2 - Condition Assessment - previously presented to Council and included in appendix
3) Phase 3 - Facility Plan (Attachment 1) - consider motion approving tonight to Council
Tonight’s request is to consider adopting the Wastewater Treatment Plant’s Facility Plan Update. This was discussed at the June 8, 2021 City Council work session. As part of the Facility Plan, Jacobs Engineering Group updated the Wastewater Treatment Plant’s Facility Plan from 2016. The objectives of this Facility Study update included:
1) Review and update projected flows and loads to 2040.
2) Review the 2016 Facility Plan improvements, document the updated status of improvements that have already been completed, and identify additional improvement alternatives that were uncovered as part of the Operational Assessment and Condition Assessment. Provide updated cost estimates for updates and revisions that are identified.
3) Review the 2016 Facility Plan project costs and provide updated cost summaries based on the status of improvements that are already completed and the updates and revisions identified for this Facility Plan Update.
As part of the flows and loads projections through 2040, the following plant influent load projections were identified in Table 2-5 of the Facility Plan Update which is listed below.
|
Table 2-5. Design Capacity and Projected Flows and Loads |
|
Item |
Original/Permitted Design Basisa |
Updated Design Basisb |
2025 |
2030 |
2035 |
2040 |
|
Population |
|
|
23,228 |
24,174 |
25,155 |
26,177 |
|
AWW Flow (mgd) |
5.2 |
5.2 |
3.25 |
3.38 |
3.51 |
3.65 |
|
CBOD5 - Average Day (lb/d) |
6,200 |
7,440 |
5,881 |
6,010 |
6,145 |
6,285 |
|
CBOD5 - Max Month (lb/d) |
7,999 |
9,239 |
7,504 |
7,657 |
7,817 |
7,984 |
|
TSS - Average Day (lb/d) |
5,001 |
6,001 |
5,855 |
6,040 |
6,240 |
6,444 |
|
TSS - Max Month (lb/d) |
6,400 |
7,400 |
8,817 |
9,118 |
9,432 |
9,758 |
|
a From Wastewater Treatment Facilities Improvements contract drawings (Bolton & Menk, Inc., 1999) and Northfield Wastewater Treatment Facility NPDES permit issued June 1, 2020 b From 2005 letter attachment to Wastewater Treatment Facility Plan (Bolton & Menk, Inc., 2016) |
Based upon the level of TSS above the Updated Design Basis, Jacobs along with Kruger (now Veolia) completed a further review of the loading capacity of the Wastewater Treatment Plant. The Veolia team indicated that because Northfield’s installation was one of the first of its kind, the design tools used for sizing were more conservative than the design tools used today for sizing new BAF plants. Veolia offered to review the Northfield performance data and model the plant’s performance using their latest process design tools. Their results confirmed the existing 10 cell BAF process can handle the future flow and load cases through 2040 easily with 10 cells in service and can even handle more flow or higher strength wastewater. Based on Veolia’s recommendation the City will be able to handle an influent load between 10,000 and 17,500 pounds per day of Total Suspended Solids. This indicated the City will have the ability to handle the influent load for TSS past 2040 projections.
The Facility Plan Updated costs to all projects from the 2016 Facility Plan and identified additional projects to be completed at the WWTP. Table 4-2 of the Facility Plan lays out the implementation plan with the project costs based on 2021 dollars for a total of $14,694,356. When staff develops the Capital Improvement Plan, staff will allocate inflation costs for the projects. Staff is working with Baker Tilly to update the Rate Study that was completed in 2018 to determine if the current rate adjustments are adequate for funding the projects.
|
Table 4-2. Implementation and Spending Schedule |
|
Item |
2022-2025 |
2026-2030 |
|
Liquid Sludge Storage |
$3,820,313 |
|
|
Biosolids Cake Storage |
|
$3,945,875 |
|
Influent Lift Pumps |
$720,000 |
|
|
Preliminary Treatment |
|
$300,000 |
|
Primary Clarification |
$354,000 |
|
|
Process Lift Pumps |
|
$210,000 |
|
BAF Blower Replacement |
$1,901,600 |
|
|
Control System and Card Access System Upgrades |
$864,000 |
|
|
HVAC Equipment Replacement |
$215,568 |
|
|
Water Supply System |
|
$1,000,000 |
|
Roof Replacement |
$763,000 |
|
|
Standby Generator |
|
$600,000 |
|
Total |
$8,638,481 |
$6,055,875 |
Tentative Timelines:
Consideration of the final Wastewater Treatment Plant Facility Plan tonight.