Palo Area of Interest (Palo, Ionia County)
EGLE Site Lead: Sydney Ruhala, RuhalaS@michigan.gov or 517-599-5356. Webpage last updated November 16, 2021.
As part of the Industrial Pretreatment Program (IPP) PFAS Initiative, the Michigan Department of Environment, Great Lakes, and Energy (EGLE), sampled the effluent (i.e. the treated wastewater discharged from the treatment plant) and biosolids for PFAS at the city of Ionia Wastewater Treatment Plant (WWTP). Results indicated that high levels of PFAS, specifically PFOS, were being passed through the treatment process at the plant. PFOS levels were 635 parts per trillion (ppt) in the effluent and 983 parts per billion (ppb) in the biosolids.
Biosolids are the nutrient-rich organic materials resulting from the treatment of domestic sewage in a WWTP. Biosolids are a beneficial resource, contain essential plant nutrient and organic matter, and are recycled as a fertilizer and soil amendment.
Under EGLE's Water Resources Division (WRD), the city of Ionia has an approved Residuals Management Plan, which has allowed the WWTP to land apply biosolids produced at the plant since 2000. Due to the high levels of PFOS found in the biosolids, WRD evaluated land application sites that received biosolids from the city of Ionia WWTP. Three fields were identified in the Palo area and selected for screening to determine if there is any impact from the land application of PFAS contaminated biosolids to the soil, groundwater, and adjacent surface water bodies.
In November 2018, the city of Ionia WWTP stopped land application of biosolids and sent accumulated sludge to a landfill. The city has worked with the source of the PFOS--an industrial facility that discharges wastewater to the WWTP--to install treatment to remove PFAS at the source and have since seen significant reductions in PFOS concentrations in both the effluent and solids generated at the WWTP. As a result, EGLE approved land application of biosolids from the Ionia WWTP again in September 2020. Biosolids were applied to a new field.
- Following a field selection process which accounts for PFAS levels in biosolids, application amounts and rates, acreage used, soil types and other factors, EGLE selected the 3 fields near Palo as a priority for sampling. As of December 2020, EGLE has been unable to gain access to sample the fields.
- As a result, EGLE began testing residential drinking water wells next to the fields and in Palo. Note, estimated shallow groundwater flow in this region is to the east, towards Prairie Creek, indicating that Palo is likely located upgradient (i.e. in the opposite direction of groundwater flow) of Biosolids Field #3.
- In February and March 2021, the Michigan Department of Health and Human Services (MDHHS) resampled 24 residentials wells that had been previously sampled by EGLE and two new wells. This resampling effort was conducted to assess long term exposures to PFAS in drinking water. No new exceedances of Michigan Part 201 criteria were detected.
- WRD continues to work with the landowner to obtain permission to sample the biosolids fields.
- EGLE will continue to work to determine the extent of PFAS contamination in Palo and identify additional potential sources (i.e. in addition to the potential biosolids source). EGLE will expand residential drinking water well testing in Palo if determined to be necessary.
Sampling Results Summary
Type of Sample
Date Sampled (or Range)
Number of Sample Results Received
Number of Samples above Criteria*
|Drinking Water (Residential Wells)||July 2020 - March 2-21||8||0|
|Groundwater||November 2021||8||Results pending|
|Surface Water||November 2021||4||Results pending|
*Residential well and groundwater monitoring well results are compared to EGLE Part 201 Criteria for 7 PFAS: PFOS (16 ppt), PFOA (8 ppt), PFNA (6 ppt), PFHxS (51 ppt), PFHxA (400,000 ppt), PFBS (420 ppt), and HFPO-DA (370 ppt).
*Surface water samples are compared to Rule 57 non-drinking water values of 12 ppt for PFOS and 12,000 ppt for PFOA.
- On August 3, 2020, new Part 201 Criteria went into effect. Historical sampling data compared to Part 201 Criteria >70 ppt is captured in the historical timeline below.
For more information on biosolids, visit PFAS and Biosolids Frequently Asked Questions.
- On July 11, 2019, EGLE contractors collected samples of water from 7 residential drinking water wells next to the biosolids fields (phase 1 sampling), 3 in Montcalm County and 4 in Ionia County. Testing showed that of the 7 wells, 4 were non-detect for PFAS. PFAS was detected in 3 wells, all of which were below the United States Environmental Protection Agency (EPA) lifetime health advisory level of 70 ppt for PFOA and PFOS. State and local health officials offered water filters to all three households with PFAS found in their water.
- On September 19, 2019, EGLE contractors collected samples of water from 12 more residential drinking water wells next to the fields and within Palo (phase 2 sampling), 3 in Montcalm County and 9 in Ionia County. Testing showed that of the 12 wells, 8 were non-detect for PFAS. PFAS was detected in 4 wells, all of which were below the EPA lifetime health advisory level of 70 ppt for PFOA and PFOS. State and local health officials offered water filters to all four households with PFAS found in their water.
- Due to the PFAS detections in residential drinking water wells in the phase 1 and phase 2 sampling events, EGLE expanded residential drinking water well testing in Palo to determine the extent of PFAS contamination and identify potential sources.
- On February 27, 2020, EGLE held a community meeting at the Boyce Elementary School to discuss phase 3 sampling with the residents and answer questions. 38 parcels, all in Ionia County, were identified for residential drinking water well testing during phase 3. The number of wells tested was dependent on permission from the residents.
- On March 18, 2020, EGLE contractors collected samples of water from 12 more residential drinking water wells within Palo (phase 3 sampling), all in Ionia County. Testing showed that of the 12 wells, 9 were non-detect for PFAS. PFAS was detected in 3 wells, one of which was above the EPA lifetime health advisory level of 70 ppt for PFOA and PFOS. State and local health officials offered water filters to two of the households with PFAS found in their water, as well as two homes nearby which had not yet been tested.
- On July 16, 2020 EGLE contractors collected samples from 6 more residential drinking water wells within Palo (remaining phase 3 sampling), all in Ionia County. Results showed that of the 6 wells, 4 were non-detect for PFAS. PFAS was detected in 2 wells, both of which were below Michigan Part 201 Criteria. State and local health officials offered a water filter to one of the two households with PFAS detected in their water.
Historical Sampling Chart: data is reflective of criteria prior to 8/3/2020:
PFOS + PFOA Only
This chart reflects data received prior to 8/3/2020.
Type of Sample
# of Samples
# of Results Received
# of Non-detects
# Between Non-detect and standard*
Drinking Water (Residential Wells)
July 2019 - March 2020
1* Residential well results are compared to the EPA LHA of 70 ppt PFOS+PFOA.
- On September 29, 2021, EGLE contractors collected samples from 2 more residential drinking water wells within Palo, both in Ionia County. Results showed that of the 2 wells, 1 was non-detect for PFAS. PFAS was detected in the second well, however results were below drinking water criteria.
- In September and October 2021 EGLE contractors installed eight shallow groundwater monitoring wells in Palo to determine groundwater flow direction and to try to identify the source of PFAS detected in groundwater. EGLE received a permit from the Ionia County Road Commission to install the monitoring wells in the public right-of-way.