STATE OF MINNESOTA MINNESOTA POLLUTION CONTROL AGENCY · PDF fileSludge Dewatering: Thickened...

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STATE OF MINNESOTA MINNESOTA POLLUTION CONTROL AGENCY

In the Matter of the Decision on the Need for an Environmental Impact Statement for the Proposed Metropolitan Wastewater Treatment Plant Solids Processing Improvements St. Paul, Minnesota

FINDINGS OF FACT AND CONCLUSIONS

The Metropolitan Council, Environmental Services Division (MCES) is proposing to substantially renovate the wastewater solids processing system at the Metropolitan Wastewater Treatment Plant (Metro Plant) in Saint Paul. The MCES proposes to replace six existing multiple hearth incinerators (MHIs) with three fluid bed incinerators (FBIs) and an alkaline stabilization system that will produce biosolids for agricultural utilization. Pursuant to Minn. R. 4410.1000, subp.3D, the Minnesota Pollution Control Agency (MPCA) staff has prepared a voluntary Environmental Assessment Worksheet (EAW) for the project. Based on the EAW and comments or information received during the EAW comment period, the MPCA hereby makes the following Findings of Fact and Conclusions.

FINDINGS OF FACT

PROJECT DESCRIPTION

1. Sludge Dewatering: Thickened primary and waste activated sludge will be continuously pumped from sludge storage tanks to two sludge holding tanks in the new Solids Management Building. The equalized solids stream will be pumped from the sludge holding tanks to the high solids dewatering centrifuges, which increase the solids concentration from 5 percent to approximately 30 percent. To aid in the dewatering process, a dilute polymer solution will be added to the solids stream before being dewatered in the centrifuges. Polymers facilitate the separation of water from the sludge mass in the dewatering process. The number of operating dewatering centrifuges needed depends upon the quantity and characteristics of the solids stream. With an allowance for maintenance, eight dewatering centrifuges will ultimately be needed.

2. Fluid Bed Incinerators: Dewatered sludge, referred to as cake, will discharge from the bottom of

the centrifuge enclosure into storage bins. The dewatered cake will be pumped into the FBIs at near constant rates to maintain a stable combustion process. While operating within design conditions, the three FBIs will sustain combustion without the addition of supplemental fuel, such as natural gas or fuel oil. Supplemental fuels will be used during incinerator start-up.

3. Energy Recovery: Each pound of volatile sludge has a heat value of approximately

10,000 British Thermal Units (BTUs). Typically, 77 percent of the Metro Plant’s wastewater solids are volatile. Based on these heat values and projected annual average solids quantities for the year 2005, the total heat value of the sludge feed is estimated to be 172 million BTUs per hour. The fuel in wastewater sludge and primary scum has sufficient energy for sustainable combustion and the recovery of some surplus heat. Two air-to-air heat exchangers and one waste heat boiler per FBI train will be used for heat recovery. The first (or primary) heat exchanger will capture heat from the FBI exhaust stream to preheat the FBI supply air. A waste heat boiler

Metropolitan Wastewater Treatment Plant Solids Processing Improvements Findings of Fact St. Paul, Minnesota and Conclusions

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will extract additional exhaust stream heat from the primary heat exchanger. Steam from the waste heat boilers will be harnessed to produce about 3,000 kilowatts (kW) of electrical power. Exhaust air from the waste heat boiler will pass through a dry electrostatic precipitator (ESP) for removal of dry ash and then enter the secondary air to air heat exchanger. This heat exchanger will transfer heat from the exhaust air stream upstream of the wet scrubbers to downstream of the wet scrubbers. Wet scrubbing will decrease the exhaust stream temperature, which can result in moisture condensing in the exhaust stack. By capturing some of the residual heat in the exhaust stream upstream of the wet scrubbers, that heat added back to the air stream downstream of the wet scrubbers will elevate the air stream temperature. This addition of heat and heat produced in the induced draft fan will effectively increase the exhaust stream temperature to about 250º F as it enters the discharge stack. The higher stack temperature will promote plume dispersion, significantly reduce corrosion in the stack, and reduce the appearance of a steam plume from the stack.

4. Ash Handling: Dry particulates collected in the waste heat boiler and the dry ESP will be

pneumatically conveyed to the existing ash silos. The silos are equipped with a baghouse for capture of the fine ash dust. Approximately 30 days of ash storage, at the projected year 2005 annual average plant loadings, will be provided. The MCES has a contract for the utilization of the incinerator ash as a component of building products or soil amendments. Beneficial re-use of ash will continue.

5. Alkaline Stabilization: During periods of peak solids loading or when an FBI is out of service,

residual wastewater solids not incinerated will be mixed with alkaline materials to raise the pH and temperature of the mixture to levels that achieve the U.S. Environmental Protection Agency (USEPA) and MPCA criteria for agricultural application of the biosolids. Since the elevated pH will release odorous ammonia and hydrogen sulfide, alkaline material production areas will be enclosed. Odorous gases will be captured and returned to the liquid treatment process. Alkaline stabilization is a chemical process designed to convert solids into a biosolids product suitable for agricultural application. Alkaline and other admixtures that may be mixed with the cake include lime and/or cement kiln dust. The alkaline stabilization facility will have the capacity to stabilize approximately 188 dry tons per day of cake.

6. FBI Air Pollution Control System: All FBI exhaust gases will be treated in a four-step process

consisting of a mercury control system, dry ESP, wet scrubbing, and wet ESP. The mercury control system is expected to be comprised of an activated carbon injection system. The dry ESP will remove up to 99 percent of the particulates in the exhaust stream including the activated carbon granules onto which mercury is absorbed. Wet scrubbing will then lower the temperature of the gas stream to condense volatile compounds and remove acid gases, such as sulfur dioxide (SO2) and hydrogen chloride. The wet ESP will remove volatile compounds condensed in the wet scrubbers and the remaining particulates and heavy metals, such as lead (Pb) and cadmium (Cd). The exact details of the air pollution control system may vary depending upon which contractor is selected to design and build the FBIs. However, any design alternatives proposed by the FBI design/build contractor must meet the same performance specifications.


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7. Exhaust Stacks: Exhaust air will be pulled through the air pollution control processes and

discharged into the stack by the induced draft fan on each train. Each exhaust stack will extend vertically to an elevation of 105 feet above grade. The three stacks will be encased in one stack housing. Each stack will be four feet in diameter.

8. Ash utilization: The MCES has a contract for the utilization of the incinerator ash as a

component of building products or soil amendments for land application. Almost all of the mercury removed from the FBI stack gas will be recovered with the dry ash in the ESP. Mercury concentrations in the ash will comply with the ash utilization permits described in Section 20.a.2.1. Should ash be mixed with sludge for land application, the biosolids product will comply with the limits established by 503 regulation. Beneficial re-use of ash will continue. Re-use will not include any heating process unless flue gas mercury control is provided. Little or no mercury is expected to be collected in the wet ash. Any minor amount of mercury in the wet scrubber will recycle back through the liquid treatment process and be recaptured. The MCES will continue to meet both effluent and air emission permit requirements for mercury.

9. Dewatering Centrifuge Emissions Control: The centrifuge discharge hoppers and the sludge bins

will be vented through ducting to the FBIs through fluidizing air blowers. All emissions of odorous compounds from dewatering and sludge cake handling will be contained and will be treated in the incinerators by thermal oxidation. There will normally be at least one FBI in operation at all times, therefore during start-up of an FBI, the potential odorous emissions will be treated by the operating FBI. However, during initial dewatering start-up, it may be necessary to divert the sludge to alkaline stabilization until the first FBI is brought on line. This start-up period, during which time a portion of the potentially odorous air stream is not treated, is temporary and is not expected to last more than two months.

10. Alkaline Stabilization Air Pollution and Odor Control: Odor control will be provided for the

truck-loading bay, alkaline mixers, and (if constructed) the three storage cells to control the release of odors. Air collected from the alkaline stabilization facilities will be passed through cartridge filters to remove particulates to remove in excess of 99 percent of particulates. Collected particulates will either be landfilled or recycled through the solids load-in facility and fed to the FBIs. Downstream of the cartridge filters, the air will pass through four parallel packaged odor-scrubbing units. The scrubbers will be single pass, three-stage packaged absorption systems. Acid treatment in the first stage will remove ammonia, followed by two stages to treat Hydrogen Sulfide (H2S) and other compounds. This scrubbing system will be designed to achieve 99 percent removal of ammonia and H2S in the untreated air stream.

PROJECT HISTORY

11. The proposed Metropolitan Wastewater Treatment Plant Solids Processing Improvements Project (Solids Project) is not included in any of the categories for mandatory Environmental Impact Statements (EISs) or EAWs in Minn. R. ch. 4410. A discretionary EAW was prepared at the request of the MCES pursuant to Minn. R 4410.1000, subp. 3D.

12. An EAW was prepared on the proposed project and distributed to the Environmental Quality

Board mailing list and other interested parties on February 2, 2001.

13. A press release containing the notice of availability of the EAW for public review was provided


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to media serving the project area on February 5, 2001.

14. The public comment period for the EAW began on February 5, 2001, and ended on March 7, 2001. Six comment letters were received during the 30-day comment period. Responses to comments received have been prepared by the MPCA staff and are hereby incorporated by reference. Comment letters were received from:

• Sharon Anderson, Transportation Planner, Metropolitan Division, Minnesota Department

of Transportation • John Westley, Director-All For the Earth • Dana A. Donatucci, Ph. D., Associate Administrator, University of Minnesota Waste

Management and Recycling • Helen A. Boyer, Director, Environmental Services Division, Metropolitan Council • Thomas W. Balcom, Supervisor, Environmental Review Section, Office of Management

and Budget Services, Minnesota Department of Natural Resources • Larry Zangs, Project Facilitator, Department of License Inspection and Environmental

Protection, City of Saint Paul (e-mail) CRITERIA FOR DETERMINING THE POTENTIAL FOR SIGNIFICANT ENVIRONMENTAL EFFECTS

15. In deciding whether a project has the potential for significant environmental effects, the MPCA must consider the four factors set out in Minn. R. 4410.1700, subp. 7. These criteria are:

A) the type, extent, and reversibility of environmental effects; B) cumulative potential effects of related or anticipated future projects; C) the extent to which the environmental effects are subject to mitigation by ongoing public

regulatory authority; and D) the extent to which environmental effects can be anticipated and controlled as a result of

other available environmental studies undertaken by public agencies or the project proposer, including other EISs.

The MPCA findings with respect to each of these issues are set forth below.


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TYPE, EXTENT, AND REVERSIBILITY OF ENVIRONMENTAL EFFECTS The first factor that the MPCA must consider is the "type, extent, and reversibility of environmental effects," Minn. R. 4410.1700, subp. 7.A. The MPCA findings with respect to each of these issues are set forth below.

16. Air Emissions: Estimated potential emissions from the proposed Solids Project emission sources are listed in Table I, below. Further refinements of these estimated emissions may occur as part of the air emission permitting process. Potential emissions are calculated assuming that the equipment is operated 24 hours a day and 365 days a year at the maximum capacity and at the maximum allowable emission rate. While potential emissions are important for determining air emission permitting requirements, they conservatively overstate the actual emissions.

TABLE I

Potential Emissions (tpy) Proposed Solids Processing Technology

Pollutant

FBI and Ash Handling Emissions

Alkaline Stabilization

Emissions

Boiler

Emissions

Generator Emissions

Total Solids Project

Emissions PM 41.7 9.2 3.8 0.4 55.1

PM10 27.3 9.2 3.8 0.4 40.7 SO2 39.6 0.00 13.6 0.2 53.4 NOx 205.8 0.00 30.8 13.4 250.0 VOC 15.5 0.00 1.4 0.4 17.3 CO 120.6 0.00 21.2 3.1 144.9 Pb 0.15 0.01 1.3e-4 0.0 0.16

TRS 1.0 0.4 0.0 0.0 1.4 H2S 0.0 0.4 0.0 0.0 0.4

HsSO4 6.9 0.0 0.0 0.0 6.9 The proposed FBI technology will result in a decrease in actual emissions in comparison to the MHI technology currently being used. Table II shows the expected air emissions associated with the FBI technology compared with the emissions that would result from processing the same solids volume with the existing MHI technology. The comparison is based on the projected solids processing rate in the year 2005. The expected emissions from the FBI technology are lower than projected emissions from the existing MHI technology for all air pollutants, except SO2. (Tables I and II show a small increase in H2S emissions from the alkaline stabilization process; this is also reflected in the Total Solids Project Emissions Column.)


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TABLE II COMPARISON OF EXPECTED EMISSIONS FOR

THE PROPOSED TECHNOLOGY WITH THE EXISTING MHI TECHNOLOGY1

Solids Processing Improvements Project

Pollutant Proposed Solids Processing Technology Existing Technology

Actual Emission Change (tpy)

Expected FBI and Ash Handling Emissions

(tpy)

Expected Alkaline

Stabilization Emissions

(tpy)

Total Expected FBI and

Stabilization Emissions

(tpy)

Projected Multiple Hearth

Incinerator Emissions

(tpy)

PM PM10 SO2 NOX VOC CO Pb TRS H2S H2SO4

14.6 14.6 29.3

164.1 12.4 96.2 0.07 0.8 0

5.5

10.4 10.4 0.00 0.00 0.00 0.00 0.03 0.4 0.4 0.0

25.0 25.0 29.3

164.1 12.4 96.3 0.1 1.2 0.4 5.5

48.3 37.1 13.7

499.3 14.9

900.7 0.25 11.2

0 20.4

-23.3 -12.1 15.6

-335.2 -2.6

-804.5 -0.15 -10.0 0.4

-14.9 Air dispersion modeling was performed to evaluate the potential ambient concentrations of

carbon monoxide (CO), nitrogen oxides (NOx), SO2, and particulate matter less than ten microns (PM10) that would be predicted to result from the Metro Plant emissions after implementation of the Solids Project. Table 7 of the EAW presents the highest criteria pollutant ambient concentrations that are predicted to result from all of the Metro Plant emission sources for all of the applicable averaging periods to facilitate comparison with the ambient air quality standards. Modeled concentrations following the implementation of the Solids Project are below the National and Minnesota Ambient Air Quality Standards.

17. Air Toxics: The air pollution control systems to be applied to the FBIs will result in lower

emissions of metals and other particulates. Further, the decommissioning of the Zimpro™ and Rotating Biological Surfaces systems will result in reduced emissions of H2S. Ammonia and H2S emissions generated by the new alkaline stabilization processes will be controlled by a three-stage scrubber. The first stage acid scrubber will control ammonia gases. More than 99 percent of the H2S emissions, which are also generated by the alkaline stabilization processes, will be eliminated by the last two stages. Sources other than the solids processes also generate toxic air pollutant emissions at the plant. In addition to the emission reductions that will be achieved with the Solids Project, the MCES also plans to modify the primary liquid treatment processes, which will result in additional capture and control of H2S and other toxic air contaminants.


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18. The Air Toxics Review (ATR): An ATR is required when an EAW is prepared for an air emission facility. Because an EAW was prepared for this project, the MCES was required to conduct an ATR. The ATR evaluated the potential for inhalation health effects (cancer and non-cancer) to occur as a result of exposure to chemicals emitted by the proposed MCES facility. The analysis indicated that the proposed facility emissions would not exceed applicable MPCA and Minnesota Department of Health (MDH) and USEPA standards. Potential health effects were quantified for chemicals emitted to the air from the facility that had calculable emission rate estimates and State or Federal health criteria for the inhalation pathway of exposure. Only incremental human health risks from the MCES facility (both existing and proposed) have been quantified, (i.e., risks from neighboring sources of air pollution are not represented in the analysis). In addition, the current ATR process, by policy, does not evaluate ecological risks. Accordingly, an environmental risk assessment was not required as part of this ATR. MCES identified 91 chemicals emitted to the air from their facility. Of those, 58 chemicals had State or Federal inhalation health criteria approved by MPCA for use in the ATR. These 58 chemicals were quantitatively evaluated for potential health effects in the study (i.e., risk estimates were calculated for these 58 chemicals). The 58 chemicals that were quantitatively evaluated are referred to as chemicals of concern (COC). Fifty-seven COCs were evaluated for chronic (i.e., long-term) non-cancer and cancer health effects and 21 COCs were evaluated for acute (i.e., short-term) non-cancer health effects. Potential risks were calculated for the maximum permitted air emissions of COCs from the facility under the proposed operating conditions. The cancer risk/chemical hazard results calculated in the ATR for the off-site worker and residential receptor populations affected by the facility are summarized below. All of these risks/hazards were calculated using either State or Federal health criteria. With respect to the results of this study, the only risks/hazards calculated to exceed applicable de minimis risk levels or hazard indices were for acute exposure to adjacent workers (workers outside the Metro Plant’s boundaries in locations adjacent to the Metro Plant).

Excess Lifetime Cancer Risks:

Receptor Population Risk Level Comment Off-site Workers 7E-07 Less than MDH’s de minimus risk level of 1 x 10-5 Off-site Residents 2E-06 Less than MDH’s de minimus risk level of 1 x 10-5

Chronic Chemical Hazards:

Receptor Population Hazard Index Comment Off-site Workers 0.4 Less than MPCA’s de minimus hazard index of 1.0 Off-site Residents 0.2 Less than MPCA’s de minimus hazard index of 1.0


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Acute Chemical Hazards:

Receptor Population Hazard Index Comment Off-site Workers (Receptor 8)

4 Greater than MPCA’s de minimus hazard index of 1.0

Off-site Workers (Receptor 4)

2 Greater than MPCA’s de minimus hazard index of 1.0

Off-site Residents 0.6 Less than MPCA’s de minimus hazard index of 1.0

Hydrogen sulfide (H2S) is the chemical primarily contributing to the potential acute chemical hazards at the worker-receptor 4 and worker-receptor 8 locations. The term de minimis is defined as follows: The risk level at or below which adverse noncancer health effects are not expected. It is presumed that when a hazard index below the de minimus level is predicted, the facility may be permitted with confidence. When (as in this case) a hazard index above the de minimus level is predicted, the facility may still be permitted with confidence because an ATR is a screening level analysis that uses conservative assumptions. The conservative assumptions, plus the additional analysis conducted by MCES and independently reviewed by MPCA, which is discussed below, lead the MPCA to conclude that the actual H2S levels in the ambient air will be lower than the levels predicted in the ATR. The conservative assumptions in the ATR for this case include, but are not limited to, the following:

• This ATR modeled concentrations of H2S from twelve sources and concentrations of toluene and xylenes from an additional twenty sources located within the Metro Plant, including the future solids project and the liquids processing system. (The liquids processing system is not part of the solids project that is the subject of the EAW.) Meteorological data employed in the modeling was that from the last five years. For each given source, the worst one-hour concentration in the five-year period was calculated and the 32 concentrations were summed. This is conservative because the highest one-hour off-site concentrations were demonstrated to have occurred during different hours for different sources and on different days for different sources. It is worth noting that 48 percent of the total Hazard Index at receptor 8 is attributable to H2S from the gravity thickening tanks, and 23 percent is attributable to xylene from the paint booths. MCES is currently investigating control alternatives for these H2S sources.

• The emission factors used were based on maximum potential to emit (PTE). This approach is conservative because not all sources may be operating at their maximum level simultaneously, and certainly not likely all on the occasion of the worst meteorological conditions for the given receptor.

However, since the ATR indicated an exceedence of the de minimus acute hazard index for off-site workers it was appropriate to verify that the result was conservatively overstated by performing additional work to provide a refined analysis. This analysis was submitted by MCES as an addendum to the ATR. MPCA technical staff have reviewed and approved this analysis.

Both the analysis and the MPCA’s evaluation thereof are available for public review. In the


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supplemental analysis, the MCES modeled the 14 individual sources (that contributed 96 percent of the cumulative risk at receptor 8) cumulatively to find the highest one-hour concentrations from all sources. The results of this refined analysis indicate that the acute inhalation hazard index at worker-receptor 8 decreased to 1.3, and the acute inhalation hazard index at worker-receptor 4 decreased to less than 1.0. The predicted exceedence of the de minimus hazard index of 1.0 at worker-receptor 8 under this additional analysis is conceived by the MPCA staff not to be significant, for the following reasons:

• The prediction assumes that all 14 emission sources will be operating at their maximum potential to emit (PTE) simultaneously, and concurrently during those hourly-averaged meteorological conditions of the last five years that produced the greatest off-site impact. Such conditions might exist during a mere handful of hours during the five years, if at all.

• The acute H2S hazard index is conservative, as it is based on the proposed Health Risk Value (HRV) of 80 μg/m3

. The HRV in turn is based on a toxicity study that reported the lowest acute effect (respiratory irritation) concentration at 1400 μg/m3. It is noted that the HRV is not considered a regulatory limit; nor is it considered a “bright line” because a safety factor approach is applied to published toxic concentrations upon which the HRVs are based.

• The prediction assumes that a worker will be located at the receptor point, during these worst meteorological conditions, while the 14 emission sources are operating concurrently at their PTE.

• Any elevated air concentration of H2S that may result in higher hazard indices at off-site locations are transient and would decrease as soon as the unusual meteorological conditions and equipment operating conditions are abated.

• The major (48 percent) source of the acute hazard index of 1.3 at receptor 8 is the gravity thickening tanks, part of the existing liquids processing units and not a part of the solids project that is the subject of this EAW. MCES is currently investigating control alternatives for this H2S source. The MCES anticipates addressing this odor source as part of its ongoing odor reduction efforts.

Additionally, MCES has agreed to a permit condition that will require them to monitor for H2S when the Solids Processing Improvements are completed in 2005. MCES has also agreed to prepare and submit Pollution Prevention Plans for the paints used in the paint booth (the source of xylene, methanol, and trimethylbenzene emissions). As a result of these actions, it is expected that monitored levels of H2S in the ambient air will be lower than the levels predicted by the computer program used in the ATR.

The MPCA finds that the Metro Solids project will not result in a significant health risk from air toxics.

19. Multi-pathway Risk Assessment Results: Many of the emission substances that were evaluated in the ATR are environmentally persistent metals such as arsenic, cadmium, chromium, lead, and nickel. Therefore, MCES supplemented the required inhalation analyses with a multi-pathway


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health risk assessment. In the multi-pathway assessment, particle deposition onto surface soil, surface water, home gardens, etc. were modeled. Subsequent chemical intakes calculated for human populations from various inhalation and non-inhalation exposure pathways were then quantified and summed. These doses were evaluated using USEPA health criteria.

For the study, MCES utilized average potential-to-emit emission rates for the COCs, rather than

maximum potential-to-emit rates as were utilized in both inhalation risk assessments (pre- and post-modification assessments). Average potential-to-emit emission rates result in more realistic, albeit less conservative risk estimates than do maximum potential-to-emit rates. The calculated excess lifetime cancer risk was below the State’s de minimus value of 1 × 10-5 for residents, anglers, and off-property workers at every receptor location. The predicted cumulative HIs for chronic non-cancer health effects were also below State’s de minimus value of 1.0 for every residential and fisher receptor. Multi-pathway assessments do not evaluate acute exposure. Using MCES’ procedures, MPCA’s technical review team reassessed the facility’s multi-pathway risks using maximum potential-to-emit emission rates and found no significant risks. The project will not result in cancer risk levels or hazard indices above the MDH guidelines. Based upon the multi-pathway analysis prepared by the MCES and reviewed and approved by the MPCA staff, the MPCA finds that the facility poses no significant risks to human health. The multi-pathway analysis also showed no lead hazard for the public, and the calculated maximum infant dose of polychlorinated dioxins/furans through breast milk is less than what is currently considered background exposure to these chemicals. The MPCA finds that the project poses no significant health risk to humans due to lead, dioxins, or furans. The multi-pathway study evaluated, by a comparative analysis, pre- and post-mercury emissions from the facility. Post-modification mercury emissions are expected to be 70 percent lower than pre-modification emissions, based on MCES’s stated reduction goals. If emissions are reduced by 70 percent, it would be expected that any associated mercury deposition into nearby lakes and the Mississippi River to be reduced. The actual percentage decrease would depend upon the form of mercury emitted both pre- and post-modification and the extent of atmospheric oxidation of elemental mercury that occurs in the region. Based upon MCES’s reduction goals, the MPCA finds that the facility will accomplish a significant reduction in mercury emissions into the environment, and that it will not have a significant adverse environmental effect.

20. Mercury: Mercury is a toxic air contaminant that has received much attention in recent years.

Most of the mercury in the wastewater influent ends up in the sludge and can end up in the incinerator emissions. The mercury emission rate is and will continue to remain far below the regulatory limit, mainly because that limit was established prior to the availability of modern test equipment. During the past several years, the average mercury loading in the sludge fed to the MHIs has been decreasing to the current average of less than 250 grams per day, resulting in actual annual emissions of less than 0.1 tons per year (tpy). The total mass of mercury in the sludge, even before reductions achieved with the stack emission control system, is less than the regulatory limit of 3,200 grams per day (1.3 tpy). The MCES submitted a Voluntary Mercury Reduction Agreement (VMRA) on December 28, 2000. The future plans for reductions entailed in the VMRA go well beyond any current regulatory requirements, including the enhanced mercury removal system incorporating activated carbon injection and dry scrubbing. Control of Industrial Sources: The MCES administers the federally delegated pre-treatment


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program which includes establishing limits, permitting, monitoring, and inspection of discharges to the Metropolitan Disposal System (MDS). Every five years, as part of the pre-treatment program, the MCES reviews the discharge limitations, including mercury that it places on the users of the MDS. Based on the results of the evaluation, the limits that dischargers to the MDS are required to meet may need to be changed. Evaluation of Dental Discharges: Survey information gathered in 1995-96, estimated mercury contributions to the collection system from dental clinics may represent up to 80 percent of the total mercury discharged. As a result, the MCES entered into a partnership with the Minnesota Dental Association to further evaluate the contributions of mercury from the dental community and to test advanced amalgam removal equipment. The MPCA finds that control of mercury at the source – pollution prevention, is a desirable approach to mercury control. Reducing stack emissions from sewage sludge incineration: The MCES will install a system to control mercury emissions from the new fluidized bed boilers-probably using an activated carbon system. This technology is expected to reduce annual mercury emissions to the air by approximately 70 percent compared to existing emission estimates. We are not aware of other sewage sludge incinerators using activated carbon to control mercury emissions. The cost for the carbon injection technology and the enhanced particulate removal technology, which is integral to the enhanced mercury removal, is approximately $5.7 million. The MCES has committed to conduct quarterly stack tests for three years following the installation and operation of the new air pollution control systems to determine the amount of mercury in the stack exhaust gases. The MPCA will incorporate the quarterly testing into the air emissions permit for the sludge incinerators.

The MPCA finds that the VMRA, control of industrial sources, dental mercury pollution prevention and stack emission reductions will result in a decrease in mercury emissions, and therefore finds that the project will not result in a significant adverse environmental effect with regards to mercury.

21. Greenhouse Gas Emissions: FBIs are superior to the currently used multiple hearth furnace incineration technology in terms of minimizing the emission of greenhouse gases. This is due primarily to much lower fossil fuel consumption rates associated with operation of FBIs compared to MHIs. The MPCA finds that changing to FBIs from the MHIs is a move towards the goal of maintaining CO2 emissions at or below 1990 levels as suggested by the recently developed Kyoto Protocol. Greenhouse gases include primarily water vapor, CO2, methane, nitrous oxide (N2O), and ozone (O3). Carbon dioxide is the greenhouse gas emitted in the largest quantity by the proposed FBIs, auxiliary boilers, and standby diesel generator. Although CO2 is a byproduct of burning sewage sludge, these CO2 emissions are not thought to increase total atmospheric CO2 because the carbon in the sludge is already part of the active carbon cycle between the atmosphere, the biosphere, and the soil portions of the lithosphere. Guidance issued by the USEPA instructs states to inventory CO2 emissions resulting from bioenergy separately from those emitted from fossil fuel combustion. Reduction strategies will be aimed primarily at reducing fossil fuel consumption. The MPCA finds that, because fossil fuels will be used only during incinerator startup, the proposed project will not constitute a significant source of increase in atmospheric CO2.


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22. Odors, noise and dust: The project will occur within the existing wastewater treatment plant in

an area zoned for industrial use. The area in the vicinity of the Metro Plant is not expected to be adversely affected by noise, dust, or odors during construction or operation. Odor is expected to be reduced as a result of the operation of the facilities constructed under this project. It may be necessary to phase in a portion of the odor control system upon initial start-up of the new dewatering equipment in the Solids Management Building. The centrifuge discharge hoppers and the sludge bins are vented through ducting to the FBIs through fluidizing air blowers. All emissions of odorous compounds from dewatering and sludge cake handling will be contained and treated in the FBIs by thermal oxidation. There will normally be at least one FBI in operation at all times, therefore during start-up of an FBI, the potential odorous emissions will be treated by the operating FBI. However, during initial dewatering start-up, it may be necessary to divert the sludge to alkaline stabilization until the first FBI is brought on line. This start-up period, during which time a portion of the potentially odorous air stream is not treated, is temporary and is not expected to last more than two months. This project is not expected to generate odor as a result of construction activities. The MPCA finds that the project will not result in increased long-term odors.

23. Ash utilization: The Metro Plant generates approximately 13,500 dry tons of ash annually.

Herzog Environmental, Inc., headquartered in St. Joseph, Missouri, with local offices, is under contract to be the material broker for the ash until the year 2005. Currently, the primary use of the ash is in construction products, which effectively contain the mercury in a form much like that of mercury ore – unavailable to the environment. Beneficial re-use of ash will continue. Re-use will not include any heating process (which could result in volatilizing of the mercury trapped in the activated carbon) unless flue gas mercury control is provided. The MPCA finds that these measures will assure that mercury is not re-released into the environment.

24. Land application of alkaline-stabilized biosolids: Use of these products is governed by federal

regulations codified at Title 40 of the Code of Federal Regulations Part 503, Subpart B (40 CFR Part 503) and by state regulations codified at Minn. R. ch. 7041. These regulations provide for, among other things, risk-based limits on the concentration of toxic metals in the biosolids and limits on the amount of metals that can be land-applied. They also provide technology-based standard to minimize pathogens, and technology-based standard to minimize vector attraction. The MPCA has issued to the MCES, a National Pollutant Discharge Elimination System/State Disposal System (NPDES/SDS) Permit regulating the land application of biosolids. At this point in the project, the MCES has not yet identified actual application sites, but several farmers have expressed interest in the product. The MCES expects that the alkaline product will be used for agricultural purposes. The MPCA finds that the regulations in effect and the conditions of the relevant permits will assure that no significant environmental impact results from the land application of biosolids.

25. Fish, wildlife, and ecologically sensitive resources: The Mississippi River flows along the

western edge of the Metro Plant. Lands designated for Pigs Eye Park, around Pigs Eye Lake, are located to the south and southeast of the Metro Plant property. Further to the southeast is the Pigs Eye Lake Scientific and Natural Area (SNA). A large heron rookery is located in the near


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vicinity of the plant. The undeveloped character of much of the land near the Metro Plant, particularly to the south and east, provides a range of habitat, which includes wetlands, floodplain forest, and grasslands. All project activity will be confined within the existing levee and floodwall for the Metro Plant. Buildings, treatment tanks, roads, and storage areas occupy most of the area inside of the levee. The MPCA finds that neither project construction nor operation will affect nearby sensitive resources.

26. Construction dewatering: It is anticipated that dewatering will be required during construction

and that a DNR Water Appropriation Permit will be required. Site dewatering can be expected to be required to an approximate elevation of 670 feet or about 30 feet below ground surface. The anticipated construction schedule will call for 12 to 18 months of dewatering. A radius of influence or radius of cone of depression, Ro, was calculated to be 306 feet using the Sichart equation. The cone of depression will be roughly 615 feet along the east-west axes and 1015 feet along the north-south axis. The created cone of depression is unlikely to extend beyond the plant boundaries and would be confined by the levee structure north and east of the site. The neighboring properties are supplied by the St. Paul municipal water supply, and are unlikely to have individual water wells shallow enough to be adversely impacted by the construction dewatering. The MPCA finds that the project will not adversely impact local aquifers or water supply wells.

27. Floodplain impacts: The Solids Project site is within the existing levee and floodwall. The

Metro Plant property falls within the 100-year floodplain according to the Federal Emergency Management Agency (FEMA) 1989 Flood Insurance Rate Map. The Metro Plant is located in the flood fringe zone as opposed to the floodway. The base flood elevation is shown as 705 feet National Geodetic Vertical Datum (NGVD). The Metro Plant’s existing levee and floodwall are designed to protect the facility from the 500-year flood. The levee elevation is approximately 716 feet NGVD. The MPCA finds that the proposed construction would not significantly compound flooding upstream of the treatment plant site, nor would it be impacted by flooding below that of the 500-year return frequency flood elevation.

28. River corridor zoning: The location of the Metro Plant within the Mississippi River

floodplain and Critical Area requires compliance with the city of St. Paul River Corridor District Zoning Code (the Code). The Code utilizes hydrologic information provided by the Flood Insurance Study for St Paul, completed under the direction of FEMA. The project area is located within District RC-4-Urban Diversified District and is subject to applicable River Corridor ordinance provisions in Chapter 65. The project is a permitted use in the RC-4 District since it is a permitted use in the underlying I-2 District. Permitted uses are subject to the standards specified in Section 65.400 et. seq, including provisions for grading and filling, protection of wildlife and vegetation, and protection of water quality. The MPCA finds that the project is not inconsistent with River corridor zoning requirements.

29. St. Paul Mississippi River corridor plan/critical area planning: The St. Paul Planning

Commission prepared the St. Paul Mississippi River Corridor Plan as part of Critical Area Planning that was adopted by the city of St. Paul in 1981 and was amended in 1987. The Plan recognized the Mississippi River as a multiple-use corridor comprised of open space, river-related industrial and commercial use, residential mixed use, public facilities, and mixed use. The Pigs Eye Floodplain Segment, including the Metro Plant site, was targeted as an area deserving immediate attention. The Metro Plant and its continued operation are provided for in


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this river segment. The proposed project should be consistent with the plan because it will be constructed within the existing levee and floodwall. The MCES will coordinate with the city of St. Paul to comply with Critical Area Program requirements. The MPCA finds that the proposed project is not inconsistent with Critical Area Planning.

30. Mississippi National River And Recreation Area (MNRRA): In November of 1988, Public Law

100-696 established the MNRRA as a unit of the National Park System (NPS). The MNRRA Plan recognizes the role of appropriate river-related industry along the river, but does not specifically address wastewater treatment plants. The MCES met with the NPS in January of 1994 as part of the Environmental Inventory process. During this meeting, the NPS staff indicated that wastewater treatment facilities are recognized as an appropriate use along the riverfront since water quality is an important issue and the facility is river related. The MCES will coordinate with MNRRA regarding this project. The MPCA finds that the proposed project is not inconsistent with MNRRA.

31. Erosion and sedimentation: Temporary erosion controls will be implemented in an effort to

curtail erosion and sediment transport and to maintain slope stability until permanent erosion controls have been adequately established. Erosion control will be maintained throughout the construction period by removing accumulated sediment, and by repairing or replacing damaged and deteriorated erosion control devices. Temporary erosion control devices typically include silt fence, straw bales, and storm sewer inlet protection. Post-construction erosion and sedimentation control is typically accomplished by establishing turf. Turf establishment will primarily consist of seeding and mulching. Sod may be placed to restore areas adjacent to maintained lawns, and in areas that may be determined to be particularly susceptible to erosion. Suitable temporary erosion control devices will be placed and maintained until permanent turf has been adequately established. The MPCA finds that erosion and sedimentation during and subsequent to construction will not constitute significant environmental effects.

32. Water Quality - Surface Water Runoff: Site runoff will continue to discharge to the wastewater treatment plant storm-water system with the exception of runoff from biosolids loadout areas. Because of the potential for minor tracking of biosolids on truck tires, etc., runoff from these areas will be captured in an on-site retention pond and discharged to the plant for treatment. The project site is a wastewater treatment plant enclosed within a levee and floodwall. Site runoff is governed by the General Stormwater Discharge NPDES/SDS Permit No. MN G610000 and the Stormwater Pollution Prevention Plan developed in accordance with the requirements of that permit. As described in the application for Permit No. MN G610000, storm water from inside of the levee and floodwall discharges into the pump station to the chlorine contact channel and into the Mississippi River.

33. Water Quality – Wastewater: The Metro Plant is an advanced secondary wastewater treatment

plant providing removal of carbonaceous biochemical oxygen demand, five-day, total suspended solids, phosphorus, and ammonium nitrate, as well as disinfection. The project is proposed to improve the Metro Plant and, directly or indirectly, the quality of effluent discharged from that facility to the Mississippi River in accordance with NPDES/SDS Permit No. MN 0029815. Concern has been raised by the DNR that centrifuge drainings containing mercury and phosphorus from dewatered sludge will complicate the efforts of plant operators to meet their


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effluent limits for those elements. It is expected that most mercury will be entrained in the sludge and removed by the carbon-injection pollution control system. It is known that sludge will release phosphorus if it becomes anaerobic. The MCES is prepared to perform whatever in-plant testing is required to assure that these elements do not become excessive in any parts of the treatment train. In any event, the facility must meet its effluent limits or face enforcement action. The MPCA finds that the proposed facility will not significantly affect water quality.

34. Solid and Hazardous Waste: The Metro Plant facility collects, separates, or generates a number

of solid wastes as a result of routine operations and maintenance. The facility recycles several materials, such as white paper, aluminum cans, cardboard, scrap metal, etc. General refuse is appropriately landfilled. Screenings are materials removed from the incoming wastewater as it passes through screens at the head of the plant. Grit is composed of small, heavy particulate matter, such as sand, which settles out of the wastewater in various treatment units. Grit and screenings will be landfilled. The Metro Plant changes-out and landfills the plastic media in the packed tower odor control equipment about once a year. The Metro Plant generates approximately 13,500 dry tons of ash annually. Presently, this ash is utilized in building material. The facility is a licensed small quantity hazardous waste generator. The MPCA finds that the various waste streams generated by the facility are subject to regulatory actions and are disposed of or recycled in appropriate ways.

35. Archaeological, historical, or architectural resources: Previous cultural resources investigations

within the Metro Plant indicate that the plant site was once the location of two historically important settlements during the first half of the 19th century: the Dakota village Kaposia and the Pigs Eye settlement. Subsurface testing indicated that portions of the plant site, including the project site, have the potential to contain a deeply buried Pre-Contact or Contact Period Archaeological site. The State Historic Preservation Officer (SHPO) concurred that an archaeological survey should be completed for the project site. In April 1998, a Phase I/II archaeological survey was conducted at the Metro Plant site. The field investigation employed a combination of machine grading and excavation as well as hand excavation. Excavation reached a maximum depth of 15 feet below the existing ground surface and included an area of approximately 3,865 square feet. While a buried native A horizon of Holocene age was identified within the project area, no archaeological resources were identified during the investigation. The geomorphological data indicates that much of the project area was poorly drained, and that the buried native surface soil has been disturbed and reworked to varying degrees. The findings indicate that there is little potential for unidentified subsurface archaeological sites to be present within the area of potential effect. Pending SHPO concurrence, no further investigation will be conducted. The MPCA finds that, pending concurrence by the SHPO, the project will have no significant effects on archaeological resources.

36. Designated parks, recreation areas, or trails: Lands south and east of the Metro Plant are

designated as Pigs Eye Park (Figure 3), and a trail corridor (unspecified location) has been shown for the area as part of the MNRRA plan. Since construction will take place inside the Metro Plant floodwall, the MPCA finds that the project will not significantly affect parks, recreation areas, or trails.

37. Scenic views and vistas: The Metro Plant is located in the “industrial riverscape” area of the

Mississippi River where the balance of open space and industrial use has been a consistent goal as referenced in many planning documents. This is a “working section” of the river with barge


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traffic, barge terminals and a variety of industries such as rail, sand and gravel, shipping operations and the St. Paul Downtown Airport. Existing and planned recreational usage (hiking, bicycling, nature study, boating, fishing, etc.) and the preservation of natural areas are important area uses. Much of the undeveloped land consists of Pigs Eye Park, including the Pigs Eye SNA, that encompasses Pigs Eye Lake. This portion of the river and adjacent designated lands are included in MNRRA, as a unit of the National Park System. Since construction is to occur in an already industrialized area, behind the Metro Plant floodwall, the MPCA finds that the project will not significantly affect scenic views and vistas.

38. Compatibility with plans and land use regulations: The Metro Plant is located within the

designated Critical Area for the Mississippi River. Under the Critical Area program, state and regional agencies follow the standards and guidelines provided in Executive Order 79-19 for permit regulation and in developing plans within their jurisdiction, and for reviewing plans, regulations, and development permit applications. The final Critical Area Standards and Guidelines recognize that certain reaches of the river can be utilized as a receiving stream for properly treated sewage. The Metro Plant and its continuance are also provided for in St. Paul’s Critical Area Plan for this river segment. The MCES will coordinate with the city of St. Paul to comply with St. Paul's River Corridor Ordinance Provisions. The MNRRA Plan recognizes the role of appropriate river-related industry along the river, but does not specifically address wastewater treatment plants. The MCES met with the NPS in January of 1994 as part of the Environmental Inventory process. During this meeting, the NPS staff indicated that wastewater treatment facilities are recognized as an appropriate use along the riverfront since water quality is an important issue and the facility is river related. The MCES will coordinate with MNRRA regarding this project. Portions of the Metro Plant site are within the runway protection zone designated by the Federal Aviation Administration for the St. Paul Downtown Airport; construction in these areas is subject to FAA review. The review has already been completed for the Solids Project. The MPCA finds that the proposed project is compatible with plans and land use regulations.


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39. Appropriateness of sludge incineration over utilization as agricultural supplements: Two commenters expressed a belief that the agricultural utilization of wastewater biosolids was preferable to incineration, inasmuch as biosolids have fertilizer value and are treated and made available by many municipalities to farmers for use as agricultural supplements. The use of biosolids as agricultural supplements is a practicable alternative to incineration and constitutes a beneficial use of resources. However, selection of treatment technologies is the responsibility of the project proposer and not the MPCA. The MCES considered alkaline stabilization and agricultural use of biosolids and in fact has made provisions to treat a part of the biosolids by alkaline stabilization. The process would take place during periods of peak solids loading or when an FBI would be out of service for any reason. The MCES has indicated that its decision to rely on the mix of alkaline stabilization and incineration was driven by several factors, including the energy costs of transporting alkaline materials, and other solids admixtures to the Metro Plant and the costs of transporting finished biosolids to farmers. Odors would also be generated during biosolids stabilization and would require control. In any event, it has not been demonstrated that the project as proposed has the potential for significant environmental effects. It is therefore not required that other alternatives be evaluated, as they would be in an EIS. The MPCA finds that the selection of treatment alternatives is a matter that is not properly before the MPCA.

CUMULATIVE POTENTIAL EFFECTS OF RELATED OR ANTICIPATED FUTURE PROJECTS The second factor that the MPCA must consider is the "cumulative potential effects of related or anticipated future projects," Minn. R. 4410.1700, subp. 7.B. The MPCA findings with respect to this factor are set forth below.

40. The proposed project is intended to provide advanced technology incinerators for the combustion of wastewater biosolids from the Metro Plant. Biosolids are currently being incinerated at the facility using old technology nearing the end of its useful life, and emitting pollutants at a level significantly higher than that expected from the proposed facility.

41. The MPCA finds that there are no related or anticipated future actions which could result in

cumulative, adverse, environmental effects. THE EXTENT TO WHICH THE ENVIRONMENTAL EFFECTS ARE SUBJECT TO MITIGATION BY ONGOING PUBLIC REGULATORY AUTHORITY The third factor that the MPCA must consider is "the extent to which the environmental effects are subject to mitigation by ongoing public regulatory authority," Minn. R. 4410.1700, subp. 7.C. The MPCA findings with respect to this factor are set forth below.

42. The following permits or approvals will be required for the project: Unit of Government Permit or Approval Required a. Federal Aviation

Administration (FAA) Notification of Proposed Construction or Alteration

b. Metropolitan Airport Commission (MAC)

Notification of Proposed Construction or Alteration (Coordinates with FAA)


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c. USEPA Spill Prevention, Control, and Countermeasure Plan d. NPS Plan review and coordination under MNRRA e. MPCA Facility Plan approval f. MPCA Plan and Specification approval g. MPCA Minnesota State Loan Funding approval h. MPCA Air Emissions Permit Amendment i. MPCA NPDES/SDS Permit j. MPCA Modification of NPDES/SDS permit to meet the

requirements of 40 CFR Part 503, Subpart B (sludge management), and Minn. R. ch. 7041

k. MPCA Above ground storage tank registration for tanks over

110 gallons l. MPCA Above ground storage tank rule requirements (Minn.

R. ch. 7151) m. MPCA Construction Stormwater Permit n. Minnesota Emergency

Response Commission and Local Fire Department

SARA Title III Chemical Notification, Planning, and Reporting

o. DNR Water Appropriation Permit amendment may be required for dewatering if more than 10,000 gallons per day (gpd) or one million gallons per year (gpy) is proposed.

p. SHPO National Historic Preservation Act Section 106 and

the Archaeological Resources Protection Act Review and Coordination. Office of the State Archaeologist coordinates with the SHPO.

q. Ramsey County Hazardous Waste Generator License r. Ramsey County Hazardous Waste Contingency Plan s. Ramsey-Washington

County Watershed District Grading Permit


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t. City of St. Paul Site Plan Review coordination regarding compliance with St. Paul Critical Area River Corridor Plan and Ordinance

u. City of St. Paul Building Permit

43. Description of the Scope of Key Permits/Approvals: a. The FAA Notification of Proposed Construction or Alteration assures that structures within

the operating areas of aircraft near airports are not encroached upon by buildings or other structures.

b. The MAC Notification of Proposed Construction or Alteration complements the FAA

permit and allows input from the operating airport. c. The USEPA Spill Prevention, Control, and Countermeasure Plan assures that permitted

facilities have contingency plans in place in case of spills of wastewater or hazardous materials.

d. The NPS Plan review and coordination under MNRRA assures that the recreational and

scenic value of MNRRA is preserved to the greatest extent possible. e. The MPCA Facility Plan approval assures the facility is designed in a manner consistent

with the water quality rules administered by the MPCA. f. The Plan and Specification approval assures the facility is constructed according to good

engineering practices g. The MPCA Minnesota State Loan Funding approval assures the proposed facility is cost-

effective and to assure the proposed technology is reasonable and a proper application of that technology.

h. The MPCA Air Emissions Permit Amendment assures that the facility is designed using

good engineering practices and in a manner consistent with the air quality rules administered by the MPCA.

i. The MPCA NPDES/SDS Permit will be required if construction ground-water dewatering

discharge is contaminated and not routed through plant but directly discharged. j. The current NPDES/SDS Permit meets the requirements of 40 CFR Part 503, Subpart B

(sludge management), and Minn. R. ch. 7041. k. The MPCA Above Ground Storage Tank registration for tanks over 110 gallons requires

certain storage tanks to be registered with the MPCA. l. The MPCA Above Ground Storage Tank rule requirements (Minn. R. ch. 7151) may apply

to some tanks over 1,100 gallons.


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m. The MPCA General Construction Stormwater Permit requires the use of Best Management Practices during construction to assure that storm water does not cause erosion and thus removal of sediment to surface water.

n. The Minnesota Emergency Response Commission and Local Fire Department SARA.

Title III Chemical Notification, Planning, and Reporting assures local fire departments and State Agency response planners, as well as citizens, are knowledgeable about the use and storage of toxic and hazardous chemicals in various buildings around the state.

o. The DNR Water Appropriation Permit amendment may be required for dewatering if more

than 10,000 gpd or one million gpy is proposed, and is intended to protect other water supply wells from impacts by the dewatering.

p. The SHPO National Historic Preservation Act Section 106 and the Archaeological

Resources Protection Act Review and Coordination is intended to assure that historic and archaeological sites are reasonably well–protected from destruction by modern construction.

q. The Ramsey County Hazardous Waste Generator License regulates hazardous waste

generation, transport, and disposal in Ramsey County. r. The Ramsey County Hazardous Waste Contingency Plan is required to be developed by

generators in case of incidents or accidents. s. The Ramsey-Washington County Watershed District Grading Permit assures that grading

is accomplished in a way that run-off does not cause sedimentation. t. The city of St. Paul Plan Review coordination assures compliance with the requirement of

the St. Paul Critical Area River Corridor Plan and Ordinance. u. The Building Permit issued by the city of St. Paul assures that the project will be consistent

with the city of St. Paul’s Building Code.

44. The MPCA finds that the permits and monitoring reports required by public regulatory authority will provide additional opportunity to mitigate the environmental effects of the project, if necessary.


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THE EXTENT TO WHICH ENVIRONMENTAL EFFECTS CAN BE ANTICIPATED AND CONTROLLED AS A RESULT OF OTHER AVAILABLE ENVIRONMENTAL STUDIES UNDERTAKEN BY PUBLIC AGENCIES OR THE PROJECT PROPOSER, INCLUDING OTHER EISs. The fourth factor that the MPCA must consider is "the extent to which environmental effects can be anticipated and controlled as a result of other available environmental studies undertaken by public agencies or the project proposer, including other EISs," Minn. R. 4410.1700, subp. 7.D. The MPCA findings with respect to this factor are set forth below.

45. The proposed wastewater biosolids (sludge) incinerator has been reviewed by the MPCA staff, as well as the DNR, Minnesota Department of Transportation, MCES, and the city of St. Paul. None of these Agencies requested the preparation of an EIS.

46. There are no elements of the project that pose the potential for significant environmental effects

which cannot be addressed in the project design and permit development processes.

47. The MPCA finds that the environmental effects of the project can be anticipated and controlled as a result of environmental review, previous environmental studies, and permitting processes undertaken by the MPCA and other regulatory agencies on similar projects.


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CONCLUSIONS 1. The EAW, the permit development process, the facility planning process, and responses prepared by

MPCA staff in response to comments on the Metropolitan Wastewater Treatment Plant Solids Processing Improvements EAW (the project), have generated information adequate to determine whether the project has the potential for significant environmental effects.

2. Areas where the potential for significant environmental effects may have existed have been

identified and appropriate mitigative measures have been incorporated into the project design and permits. The project is expected to comply with all MPCA standards.

3. Based on the criteria established in Minn. R. 4410.1700, the project does not have the potential for

significant environmental effects. 4. An Environmental Impact Statement is not required. 5. Any findings that might properly be termed conclusions and any conclusions that might properly be

termed findings are hereby adopted as such. ____________________________________ Karen A. Studders, Commissioner Minnesota Pollution Control Agency ____________________________________ Date

Minnesota Pollution Control Agency

Metropolitan Wastewater Treatment Plant Solids Processing

RESPONSES TO COMMENTS ON THE EAW

Comments Nos. 1-51 Submitted by John Westley, Director, All For the Earth COMMENT 1a: “Yes or no (y/n), the plant is being allowed to continue operating by the MPCA under air permitting that was to expire over 5 years ago?” RESPONSE 1a: A Title V permit was issued to Metropolitan Council, Environmental Services (MCES) on March 13, 2001. Prior to that, the Minnesota Pollution Control Agency (MPCA) issued Permit No. 879-90-OT-3 for the Metropolitan Wastewater Treatment Plant on July 12, 1990. On October 18, 1993, the MPCA promulgated new operating permit rules in conformance with the Clean Air Act Amendments of 1990. The new rules required that permit applications be submitted under the new program between and January 15, 1995, and February 15 1996, depending on the Standard Industrial Classification Code for the facility. MCES submitted an application for the Metropolitan Wastewater Treatment Plant in December 1995 pursuant to the operating permit rules. Under Minn. R. 7007.0350, subp. 2, a facility holding a permit scheduled to expire after October 18, 1993, that submits a timely application for a new operating permit is authorized to continue operating under the existing permit until the new operating permit is issued. COMMENT 1b: “y/n the application for the new Clean Air Act emission permits are over 5 years old?” RESPONSE 1b: The original application was dated 1995, which makes it over five years old. For the reissuance of the permit, MCES was required to provide updates and clarifications to the 1995 information as needed. COMMENT 2: “y/n, are there other outstanding MPCA permits or applications that allow continued operations or are outstanding after 5 years? If yes, give exact details and contact names for independent verifications.” RESPONSE 2: It is very common, and often the norm, to have facilities operate beyond their permit expiration date. Below are details for other incineration facilities in particular:

3M Hazardous Waste Incinerator, issued in 1989. Gary Garner, 651-458-2500. NSP Red Wing Waste Combustor, issued in 1989. Alma Allen-Webb, 612-330-5956 NSP Wilmarth Waste Combustor, issued in 1993. Alma Allen-Webb, 612-330-5956 Polk County Waste Combustor, issued in 1986. Willard Wilson, 218-435-6501 Fergus Falls Waste Combustor, issued in 1986. Mark Larson, 218-739-3467 Pope/Douglas Waste Combustor, issued in 1986. Dennis Nagle, 320-763-9342 Mayo Foundation Medical Waste Incinerator, issued in 1992. Colin Yennie, 507-266-8219

COMMENT 3: “y/n, was the USEPA notice and finding of violation of the Clean Air Act at the Metro plant considered by the MPCA in the assessment? If yes, how so? If no, why not?”

Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet RESPONSE 3: The Consent Decree developed as a result of the EPA notice and finding of violation and the EPA suit against the MCES was entered on February 6, 2001. That Consent Decree required MCES to replace the existing multiple hearth incinerators with the proposed fluidized bed incinerators and new air pollution control equipment. The choice to replace multiple hearth furnaces with fluidized bed incineration and other solids handling equipment is entirely consistent with the Consent Decree. COMMENT 4: “y/n, was the USEPA suit against the MCES Metro plant considered by the MPCA in the assessment? If yes, how so? If no, why not?” RESPONSE 4: See response to Comment 3. COMMENT 5: “y/n, were the new USEPA fine particulate matter standards considered in the assessment? If yes, provide that detailed analysis. If no, why not?” RESPONSE 5: It is presumed that the commenter is referring to the ambient air quality standards for particulate less than 2.5 microns in diameter (PM2.5). These standards were remanded to the Environmental Protection Agency (EPA) by Federal Court and are therefore not in effect. Although there are no state or federal requirements to evaluate PM2.5 emissions, a preliminary evaluation indicates that the MWWTP PM2.5 emissions would be less than the remanded standards of 65 ug/m3 and 15 ug/m3 for the 24-hour and annual averaging periods, respectively. The assessment included particulate matter less than ten microns (PM10). The PM10 results shown in the Air Toxics Review (ATR) Table 8-4 (attached) are 66 μg/m3 and 11 μg/m3, for the 24-hour and annual averaging periods respectively. The annual PM10 average concentrations from the MWWTP are less than the remanded PM2.5 standard. The 24-hour average PM10 concentration presented in ATR Table 8-4 is the second high concentration (an average of one exceedence per year allowed) while the 24-hour average PM2.5 standard was based on the 98th percentile (2 percent of concentrations could exceed 65 μg/m3 and meet the standard). It is likely that the 98th percentile PM10 concentration is less than 65 μg/m3. The MWWTP particulate sources include the fluid bed incinerators (FBIs), paint booth, material handling equipment, and boilers. The PM2.5 fraction of PM10 from the FBIs with the proposed control equipment is expected to be 47 percent (obtained from AP-42 for uncontrolled FBI emissions and size specific control equipment efficiencies). The boiler particulate emissions may be nearly all PM2.5. However, the remaining particulate sources, the paint booth and material handling sources, are expected to have very low fractions of PM2.5 included in the PM10 emissions. Therefore by presenting results for the 98th percentile concentration and including the PM2.5 fraction the MWWTP PM2.5 emissions cause impacts that are less than the remanded standards for both the 24-hour and annual averaging periods. . COMMENT 6: “What is the MPCA definition of “state-of-the-art?” RESPONSE 6: The Environmental Assessment Worksheet (EAW) uses the phrase “state-of-the-art” in reference to the pollution control equipment. Regarding mercury control, activated carbon injection represents “state-of-the-art”. There is no more effective mercury control technology in use. Regarding particulate matter, a wet electrostatic precipitator (ESP) is listed in the EPA Reasonable Available Control Technology/Best Available Control Technology (BACT)/Lowest Achievable Emissions Rate Clearinghouse as having met BACT for a sewage sludge incinerator. The Wet ESP, together in series with a Dry ESP and a Wet Scrubber, will be even more effective in removing particulate matter, metals, and acid gases than the BACT equipment required by the EPA.

2

Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet COMMENT 7: “y/n, regarding section 6.b.1, was the MPCA aware that “This proposal was reached...” not “with input” but despite the input of the vast majority of “interested citizens?” RESPONSE 7: According to the MCES staff, “Input was obtained from, and information provided to obtain input from as many stakeholders as possible. This was accomplished through community meetings; meetings with the business community, regulators, and environmental groups; an informational open house; and a town meeting. In addition, in February 1998, an informational packet was mailed to 240 interested individuals and organizations. A workshop with the Council’s Environment Committee and the public hearing were announced through public notices or news releases. In general, neighborhood residents near the plant expressed their desire to minimize future odor sources; this position supported incineration since incineration provides less opportunity for odors to be generated or released. For example, a petition was submitted to the Council with 40 signatures, consisting primarily of nearby St. Paul neighborhood residents, requesting that the Council select the fluidized bed incineration option. The accompanying letter cited odor issues related to past biosolids handling at the Metropolitan Wastewater Treatment Plant (MWWTP). In addition, the need to minimize costs, to conserve space for future liquids treatment expansion, and to minimize reliance on fossil fuels were important criteria that supported incineration. At one time, the Council had considered installing four rather than three FBIs. However, a number of metro area citizens that provided input during the evaluation process generally favored a technology that would recycle organic to the land. This was recognized as an important factor in support of land application. Therefore, on July 23, 1998, the Metropolitan Council approved the current project consisting of three FBIs, as the primary management technology combined with alkaline stabilization of biosolids for land application.” The statement in the EAW that “This proposal was reached by the MCES following lengthy study with input from interested citizens.” does not imply that all members of the public who were consulted agree with the decision made by the MCES. COMMENT 8: “y/n, a complete and accurate environmental assessment can be made without knowing if biosolids are to be stored on site?” RESPONSE 8: The ATR was performed based on the assumption that biosolids would be stored on site, which would result in a greater potential for site impacts than if they were transported immediately. If they are not stored on site, any associated impacts will not occur. In any event, the worst case assumptions were modeled. COMMENT 9: “y/n, a complete and accurate environmental assessment can be made without knowing whether the existing ash storage silos will be modified to store alkaline material or incinerator ash?” RESPONSE 9: The environmental assessment was based on an evaluation of the “worst case” alternative. As stated in Sections 6.b.4.9 and 6.b.4.11, four of the existing silos will be used for ash storage and four will be converted over to alkaline material storage. For the air toxics review, a “composite” material was used to account for variations in the alkaline materials. Emission factors were developed based on the highest concentration of a contaminant among the various materials. This ensured that a conservative “worst-case” scenario was evaluated.

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Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet COMMENT 10: “y/n, MPCA recognizes impact differences between alkaline material and incinerator ash?” RESPONSE 10: The two materials are different in terms of their origin – the processes that produce them, and in their chemical composition. Incinerator ash would, for instance, be a mixture of many elements and compounds (including mercury removed from the air pollution control equipment on the incinerators), while alkaline material will be more homogenous. Generally, the alkaline material will be lime or cement kiln dust. COMMENT 11: “6.b.2 states that ‘Many other criteria were evaluated, but did not show a difference in technologies.” What were each of these criteria (besides monetary) and the results of those evaluations? RESPONSE 11: According to the Metropolitan Council Staff, “There were several non-monetary criteria that were evaluated. These included air emissions, odor potentials, residuals (recycling organic to land), energy use, staffing requirements, public acceptance, risk, sustainability, and facility space requirements. After consideration of all criteria, fluidized bed incineration with supplemental alkaline stabilization was selected as the best treatment option.” The MPCA does not normally review the selection process used by a project proposer, or the selection of one particular technology or site over another. In this particular instance a Public Facilities Authority loan is being utilized to finance a part of the solids handling improvements, so MPCA reviews the project to assure that a cost effective analysis was done and that the chosen alternative is a cost effective solution (not necessarily the most cost effective solution). We also look at the proposed technologies to see if what is proposed is reasonable and a proper application of the technology. Once a project is proposed and an application for a permit is received, the MPCA prepares an EAW to review the potential for significant environmental effects associated with the proposal. If a Negative Declaration on the need for an Environmental Impact Statement (EIS) is obtained, the proposed project proceeds through permitting to determine that it is consistent with the environmental rules enforced by the agency. There are often many different approaches to accomplish the same goal, each of them not having potential for significant environmental effects and each consistent with environmental regulations. COMMENT 12a: “6.b.3 states that ‘More than 48 environmental groups received information on the Solids Project” y/n, did any of these groups express support for the continued incineration of sewage sludge as proposed? It further states “incineration provides less opportunity for odors to be generated or released.” RESPONSE 12a: According to the MCES staff, “A mailing was sent to 48 environmental groups inviting them to a meeting on January 13, 1998; as well as an open house on January 8, a town meeting on January 20, and a public meeting on March 26. These were part of a series of meetings (see response to question 7) held to obtain input on technologies for processing sewage sludge (solids) prior to the Council making a technology decision. In general, neighborhood residents near the plant expressed their desire to reduce odors. (See the Response to Comment 7.) COMMENT 12b: “y/n, does incinerated sewage sludge smell like burnt human excrement?” RESPONSE 12b: It smells like sewage sludge ash. Sewage sludge and human excrement are qualitatively different materials.

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Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet COMMENT 13a: “y/n, is [sic] the proposed new smokestacks closer to populated areas than the existing stacks?” RESPONSE 13a: The proposed FBI stacks are approximately 200 feet from the closest ambient boundary to the northeast and east. The existing Multiple Hearth Incinerator (MHI) stacks are approximately 1600 feet from the northeast corner of the plant property and 1300 feet from the nearest boundary, which is on the east side of the plant. The six MHI stacks are located throughout the existing Filtration and Incineration (F&I2) building. MHI 5 and 7 (SV008 and SV009) are located towards the west side of F&I2 and the other four MHIs are towards the east side of F&I2. The center of the F&I2 building is a good approximation of the six individual MHIs locations. The proposed FBI stack is approximately 950 feet east and 1300 feet north of the center of the F&I2 building. From the center of the F&I2 building, the east ambient boundary is approximately 1300 feet away. COMMENT 13b: “y/n, is [sic] the proposed new smokestacks lower than the existing stacks?” RESPONSE 13b: Two of the MHI stacks (SV008 and SV009) are currently 99 feet high (from a base elevation of 700 feet). The other four MHI stacks (SV010-SV013) are 106 feet high (base of 700 feet). The proposed FBIs stack height is 105 feet (also from a base of 700 feet). The FBI stack is one foot shorter than four MHI stacks and six feet taller than two of the MHI stacks. An FBI stack height of 130 feet was originally proposed by MCES, but was not accepted by the Federal Aviation Administration. COMMENT 13c: “y/n , do lower smokestacks mean lower points of emissions?” RESPONSE 13c: In a general sense, yes. Stacks are measured from grade, so if the terrain is basically flat, then the datum would be the same for all stack. If the terrain is not flat, the elevation of the grade itself would have to be added to the stack height. However, emission rates for the FBIs will be less than the emissions from the current multiple hearth incinerators. COMMENT 13d: “y/n, do lower smokestacks mean greater dispersions on the immediate surroundings?” RESPONSE 13d: Stack height alone is not the only factor, but it is the dominant factor. If all other factors are equal, then lower stacks result in less dispersion and a greater local impact. Other factors, however, include emission concentrations, the heights and locations of nearby buildings and terrain features, the stack gas temperature, the stack diameter, and the stack gas exit velocity. COMMENT 14: “y/n, did the assessment consider the fact that when the Seneca incinerations were stopped and solids alkalization implemented that no odor complaints were made?” RESPONSE 14: The Metropolitan Council initiated construction of improvements to the Seneca Wastewater Treatment Plant and nearby facilities in the early 1990’s to address neighborhood odor complaints. Prior to these improvements, odors were generated from a number of plant processes, including, liquids processing, sludge processing, and incineration. A citizens’ Odor Advisory Committee was formed in 1989 to advise the Council on these issues. From 1990 through 1995, capital improvements included odor control equipment for the rehabilitated incinerators, and collection and treatment of odorous emissions from various liquid treatment processes. Liquid treatment facility improvements included provision of odor control facilities at the nearby lift and meter stations, covering the preliminary and primary treatment areas of the plant and collecting and treating those odors. The citizens’Odor Advisory Committee held its last meeting on October 11, 1995, since these improvements apparently resolved neighborhood odor issues.

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Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet COMMENT 15: “y/n, did the assessment consider the fact that after the new “state of the art” Seneca incinerators began operating that the offensive odors and complaints returned?” RESPONSE 15: According to Metropolitan Council staff, their records do not indicate renewed complaints occurred when incinerators were placed back in service in October 1993. At this same time the Council was conducting 90-day tests of heat drying and alkaline stabilization facilities. A few complaints were noted regarding the operation of both of these facilities during their temporary operation. COMMENT 16: “y/n, did the assessment consider the move by Duluth’s WLSDD away from incineration towards land application?” RESPONSE 16: Western Lake Superior Sanitary District (WLSSD) has responsibility for solid waste management and wastewater treatment in Duluth and neighboring communities. Throughout the 1980’s and 1990’s the WLSSD co-incinerated municipal solid waste and wastewater sludge. In 1995, WLSSD prepared a master plan that included biosolids handling, solid waste processing, maintenance, and effluent quality as four major elements. They evaluated biosolids processing alternatives that were available and concluded that two alternatives applied – one was incineration in a new facility, and the other was land application. WLSSD chose land application for three reasons:

• Wastewater biosolids have fertilizer value and are a resource. With the relatively recent conversion of a major paper mill from free chlorine to chlorine dioxide bleaching, the biosolids are free from chlorinated contaminants such as dioxin.

• Land application sites are readily available in the area so the system is easily expandable. Continued reliance upon incineration would require new construction.

• WLSSD is located next to Lake Superior, an Outstanding Resource Value Water. While the WLSSD incinerator emissions complied with all State and Federal requirements, it is a long-term binational (US-Canadian) goal to achieve zero discharges of persistent toxics into Lake Superior, and biosolids land application is consistent with that goal.

The WLSSD plant is less than one-sixth the size of the MWWTP. The MCES has historically been able to find sufficiently large numbers of farmers to accept their wastewater biosolids. However, the large quantities of materials (both biosolids and the alkaline materials required for stabilization) result in major transportation costs. Moreover, in a rapidly expanding Metropolitan Area, it is becoming increasingly difficult to find farms at reasonable distances from the MWWTP. Biosolids management strategies that work for one facility may not do so for other facilities. COMMENT 17: “y/n, did the assessment standards of the MPCA approvals for the WLSDD project differ from the one’s used for the proposed Metro project? If yes, how so and why?” RESPONSE 17: An EAW was NOT prepared on the WLSSD project, since there is no mandatory category for EAW preparation that applies. Specific characteristics of the respective projects were considerably different, but the standards of assessment used during permit review are no different. See also the response to Comment 11. COMMENT 18: “y/n, did the MPCA documentation for the WLSDD solids projects purport that land application is more cost effective and environmentally sound than incineration? If no, provide those specific references.”

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Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet RESPONSE 18: Cost-effectiveness is not normally germane to the MPCA's review of any project. It is the responsibility of the project proposer to decide what kind of a project to build. The MPCA is responsible for conducting environmental review of a project to determine if there is a potential for significant environmental effects. The MPCA is also responsible for reviewing the permit application and facility design to assure that the project is consistent with applicable rules, and that appropriate technology is being used in an appropriate application. If a Public Facility Authority loan is being used to finance the project, as is the case with at least part of the Solids Project, the MPCA reviews the project to insure that a cost-effective alternative is being proposed. However, cost-effectiveness of a project is not at issue in an EAW. Nowhere in the rules of the Environmental Quality Board is it required that a Responsible Governmental Unit evaluate cost-effectiveness. COMMENT 19: “y/n, is 30% solids concentration from sludge dewatering required to achieve the proposed energy recovery? If no, what are the exact concentration levels required?” RESPONSE 19: The furnaces will be designed to operate at a solids concentration ranging from 26 to 32 percent, as listed in the bid specifications. The waste heat boilers and the electrical turbine and generator will be able to operate over the entire range of design conditions. COMMENT 20: “y/n, does [sic] any of the other centrifuges used by the MCES consistently achieve 30% average concentrations? If yes, provide the sites and operational data?” RESPONSE 20: The centrifuges currently in operation at the Metro plant consistently achieve an average solids concentration of 30 percent. COMMENT 21: “y/n will more pollution be generated from incineration if the 30% levels are not reached?” RESPONSE 21: Such a scenario is unlikely. The fluidized bed incinerators are required to meet the emission specifications across the entire operating range of 26 to 32 percent solids in the sludge. The incinerators have to maintain minimum operating temperatures, regardless of the moisture content of the sludge. The incinerators are equipped with auxiliary burners that will fire if temperatures drop. Emissions of pollutants such as particulate matter, metals, and sulfur dioxide are related to the amount of inert solids, metals, and sulfur in the sludge and are independent of the moisture content of the sludge. COMMENT 22: “What is the exact nature and quantities of the proposed polymer solutions to be added to the solids?” RESPONSE 22: A dilute polymer solution is added to the sludge to aid in the dewatering process. This polymer is a long-chain organic compound that is destroyed via thermal oxidation in the incinerators. Approximately six pounds of polymer per ton of sludge is added. The polymer binds the solids present in the wastewater and makes the dewatering process easier and more efficient. This polymer is not a hazardous material. The polymer is a solution of five to six percent amino-methylated polyacrylamide and 94 to 95 percent water. Approximately six pounds of polymer is added per ton of sludge. Toxicity information on the product’s Material Safety Data Sheet (MSDS) states that, even at full strength, the product is not expected to be toxic in contact with skin or by inhalation. The MSDS also states that the product is not considered toxic by ingestion and that wastes from residues can be landfilled or incinerated.

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Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet COMMENT 23: “6.b.4.5 states “While operating within design conditions, the three FBIs will sustain combustion without the addition of supplemental fuels” What are these exact design conditions? At what operational levels will supplemental fossil fuels be required?” RESPONSE 23: As listed in the bid specification, the furnaces will be designed to operate at dry solids concentrations of 26 to 32 percent. The expected operating solids content is 30 percent. If the solids concentration were to drop below 27 percent, some natural gas may need to be added to the fluidized bed in order to maintain combustion. At solids contents above 30 percent, quench water may need to be added to prevent damage to the incinerator systems. COMMENT 24: “y/n even at maximum efficiency, will 70% water concentrations have to be burned off?” RESPONSE 24: Thirty percent solids is a typical design value for fluidized bed incinerators and represents an optimum trade-off between the energy required to dewater sludge and the energy required to evaporate water in the incineration process. In addition, at solids concentrations above 30 percent, quench water may be needed in order to operate the incinerators without causing damage to the equipment. COMMENT 25: “6.b.4.b states ‘Steam from the waste heat boilers will be harnessed to produce about 3,000 kilowatts of electrical power.’ What is the gross electrical power usage of the entire FBI heat recovery systems as proposed?” RESPONSE 25: The gross electrical power usage of the entire FBI heat recovery system is approximately 200 kilowatts when the turbine is producing in excess of 3,000 kilowatts. COMMENT 26: “y/n, it would be more energy efficient to directly heat the proposed areas with the fossil fuels used for incineration?” RESPONSE 26: The FBIs only require supplemental fuel during startup and hot standby conditions. The annual supplemental fuel requirement is approximately 1,000 Million British Thermal Units (MMBTU)/yr. The annual amount of heat available for winter plant heating from the FBI heat recovery system, however, is approximately 140,000 MMBTU/yr. COMMENT 27: “y/n, will the FBI energy recovery proposal result in a net energy losses? If no, provide the comparative data.” RESPONSE 27: See response to Comment 26. COMMENT 28: “y/n, the ground dewatering proposed is an average discharge of over 90 thousand gallons per day? What are the peak dewatering levels? What is Appendix B?” RESPONSE 28: Appendix B was inadvertently deleted from the EAW and is attached to this Response to Comments as Attachment C. The average discharge rate of 63 gallons per minute represents an upper bound (high) estimate as discussed in the EAW text and shown in Appendix B. Peak storm discharge events were considered as part of this calculation. This rate would result in about 90,720 gallons per day. C0MMENT 29: “What are the ‘performance specifications’ for the FBI Air Pollution Control System?”

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Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet RESPONSE 29: The performance specifications are the bid specifications supplied by MCES, which the FBI/Air Pollution Control equipment vendor must meet. These performance specifications for the FBI incinerator system are as follows:

Pollutant Emission Rate (lbs/Dt)* CO 0.7 NOx 2.1 SO2 0.64 VOC 0.27 H2SO4 0.12 PM 0.1 PM10 0.1 Arsenic 0.00012 Beryllium 0.000004 Cadmium 0.00021 Chromium 0.0035 Lead 0.0016 Nickel 0.0014 Mercury 0.00078

* lbs/dry ton of sludge C0MMENT 30: “23.2 states ‘Modeling performed to evaluate the impacts of the projects emissions’. What is the exact nature, input data, conditions, and results of this modeling?” RESPONSE 30: Details on the modeling are described in the ATR final report that was prepared as part of the EAW process. The report was reviewed and approved by the MPCA and their risk assessment consultant, Jeffrey B. Stevens, Ph. D. of STS, Ltd. Copies of the ATR and related documents are available at the MPCA for review by interested persons. Copies of these documents have been provided to Mr. Westly. Minn. R. 4410.0200, subp. 24 Defines an evironmental asessment worksheet as “a brief document [emphasis added] which is designed to set out the basic facts necessary to determine whether an EIS is required for a proposed project or to initiate the scoping process for an EIS.” It was not the intent of, nor was it necessary for, this EAW to recapitulate the ATR. C0MMENT 31: “y/n, a complete and accurate environmental assessment can be made without knowing the exact nature of the mercury control system to be used?” RESPONSE 31: A complete and accurate environmental assessment can be made. The EAW was prepared based on a worst case assumption about the performance of an activated carbon mercury control system. The MCES has stipulated the minimum levels of mercury control in the bidding specifications. It is possible that a bidding contractor may elect to propose an alternative control technology that will control mercury emissions more effectively. C0MMENT 32: “y/n, the probable mercury control system is not in use on any other sewage incinerators?”

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Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet RESPONSE 32: Mercury control systems similar to the one proposed for the FBIs have been installed on solid waste incinerators in North America and Europe and recently on several sewage sludge incinerators in Europe. Activated carbon control has been proven on municipal and medical waste combustors in the United States. Minnesota municipal waste combustor rules are written to expect 85 percent control. C0MMENT 33: “y/n, the proposed mercury reductions from this system are estimates and have never been tested or achieved on a real operational basis?” RESPONSE 33: The proposed reductions from this system are estimates. This system has not yet been constructed. The EAW was prepared based on a worst case assumption about the performance of the mercury control system. Mercury control systems similar to the one proposed for the FBIs have been installed on municipal solid waste incinerators in North America and Europe and recently on several sewage sludge incinerators in Europe and have achieved the desired level of control. However, the proposed mercury control system has not yet been proven in a North American application. For this reason, the MPCA will not require a mercury limit in the permit at this time. The MPCA will allow the MCES to test the system before imposing enforceable limits with penalties for noncompliance. In any event, the permit limits for mercury will be far less that those currently in effect. C0MMENT 34: “y/n, 100% land applications eliminates the fossil fuel needs of incineration? What are the proposed fossil fuel needs for the FBIs?” RESPONSE 34: Land application 100 percent of biosolids would eliminate the FBI fossil fuel requirement of approximately 1,000 MMBTU/yr. A heat-dried biosolids fertilizer process, however, would require 600,000 MMBTU/yr of fossil fuel, not including the fuel that would be required to heat the plant. Alkaline stabilization would not require fossil fuel for solids processing, but would require fossil fuel to heat the plant and would result in 1.5 times more fossil fuel for product transportation as compared to the heat-dried biosolids fertilizer process. C0MMENT 35: “23.2.3 states ‘the carbon in sludge is biogenically “recycled” on a renewable basis”. When incinerating sewage sludge by what exact processes is this achieved?’ ” “What is the MPCA definition of biogenically?” “What is the MPCA definition of recycled?” RESPONSE 35: Sewage sludge is a natural phase of the carbon cycle between the atmosphere, biosphere and lithosphere. As such, it is not considered to contribute to a net increase in the carbon dioxide in the atmosphere. During incineration, the carbon is released to the atmosphere as carbon dioxide (CO2). This CO2 is then taken up by plant life in the terrestrial, aquatic, and marine environments. The plant material is then either consumed by humans and animals, which release the carbon as sewage, manure, or exhaled CO2. Both plants and animals die and decompose, releasing the carbon back to the atmosphere and the soil. Some carbon is dissolved from the atmosphere into the oceans as CO2, carbonate (CO3

-2), and bicarbonate (HCO3-1) and some is fixed with calcium in the

calcium carbonate (CaCO3) shells of marine and aquatic organisms. The carbon in wastewater sludge incorporated into soil will be decomposed by soil microbes and either respired as CO2 or incorporated into tissue and subsequently decomposed and respired. This carbon would make its way back into the environment whether it was incinerated or not. The term biogenic means the carbon is passed through living organisms as part of the cycle. There is relatively free exchange of carbon bertween the biosphere, the atmosphere, the ocean, and the soil of the lithosphere, and comparatively little exchange between the sedimentary rock of the lithosphere and the other parts of the system. The burning of fossil fuels of various types, however, results in the release of CO2 into the atmosphere.

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Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet C0MMENT 36: “y/n, alternatives to incineration are process control technologies that can be employed to reduce most species of greenhouse gas emissions?” RESPONSE 36: Other sludge disposal technologies can be used that would reduce the emissions of some greenhouse gas species at the facility site. However, emissions would be increased at locations away from the site. Alkaline stabilization with land application would require significant fossil fuel use for the transport and application of the material, as well as increase the emission of nitrous oxide (N2O) to the atmosphere. Heat drying followed by land application would require less fossil fuel for transportation than alkaline stabilized material, but this would be offset by the fossil fuel used to dry the sludge. Also, additional fossil fuel would be required to heat the plant if heat drying or alkaline stabilization were used. C0MMENT 37: “y/n, the proposed project does not meet the greenhouse gas emission reduction standards set by the Kyoto Protocol? If yes, what is the analysis supporting that claim?” RESPONSE 37: The proposed project is a step towards meeting the emissions reductions set in the Kyoto Protocol. The amount of supplemental fossil fuel needed will be significantly reduced with the installation of the FBIs. This will reduce the greenhouse gas emissions due to auxiliary fuel use by over 95% compared to the existing multiple hearth incinerators. The emissions due to the combustion of the sludge will remain the same. C0MMENT 38: “y/n, nitrogen is added to fertilizers applied to the soil that have been depleted of their natural nitrogen levels? y/n, this allows for higher yields and more efficient farming?” RESPONSE 38: Chemical or organic nitrogen is added to soils that have been depleted of their natural nitrogen levels. C0MMENT 39: “y/n, carbon based materials are naturally land and/or soil based? y/n, sewage sludge incineration displaces carbon material from its natural grounded state by releasing it into the atmosphere?” RESPONSE 39: Carbon is naturally transferred back and forth between the atmosphere, the hydrosphere (aquatic and marine), and the lithosphere (fossil fuel, limestone and other carbonaceous sedimentary rocks). Sewage sludge is a biogenic source of carbon. The carbon from the sewage sludge applied to land will decay or be ingested by the microorganisms in the soil. The respiration of these microorganisms releases CO2 directly to the atmosphere. In fact, the exchange of carbon between the atmosphere, the biosphere, and living and dead organic matter in soil occurs readily and freely. C0MMENT 40: “What are the N20 [sic] emission estimates for the proposed land applications? What is the source of the claim that N20 [sic] is 310 times more powerful than Co2 [sic]?” RESPONSE 40: The emissions estimate for N2O from the land applied sewage sludge is 440 tons/year. This was calculated from the methodology found in “Emission Inventory Improvement Program, Volume VIII, Chapter 12, Methods for Estimating Greenhouse Gas Emissions from Municipal Wastewater, October 1999, Section 4.2, N2O Emissions from Wastewater and Sludge. ICF Consulting, Washington DC, (for the Greenhouse Gas Committee, Emission Inventory Improvement Program, U.S. EPA.).” The concept of Global Warming Potential (GWP) was developed to compare the ability of a greenhouse gas to trap heat in the atmosphere relative to another gas. CO2 is usually chosen as the reference gas (GWP=1). The GWP is the ratio of global warming, or radiative forcing, from one unit mass of a

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Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet particular greenhouse gas to that of one unit mass of carbon dioxide over a period of time. The GWP of N2O over a 100 year time period is 310. (IPCC (1996) Climate Change 1995: The Science of Climate Change. Intergovernmental Panel on Climate Change; J.T. Houghton, L.G. Meira Filho, B.A. Callander, N. Harris, A. Kattenberg, and K. Maskell, eds.; Cambridge University Press. Cambridge, U.K.) C0MMENT 41: “Section 23.0 is listed as describing the MPCA Air permitting processes-Where is this information referenced?” RESPONSE 41: The MPCA air permitting process is referred to throughout Section 23 of the EAW. Specific information on the permitting process is found in Sections 23.2 and 23.4. The air permitting process requirements are contained in Minn. R. 7007. C0MMENT 42: “What is the status of the major amendment for the required MPCA operating permit?” RESPONSE 42: The MPCA is currently reviewing the application for the major amendment and is writing a draft permit. This draft permit will be put out on public notice for review prior to issuing the final permit amendment. C0MMENT 43: “y/n, have other MPCA air permits of this scope, magnitude, and similar potential impacts have been approved for amendment as proposed? If yes, provide exact circumstances and scopes.” RESPONSE 43: All changes of this and similar magnitude go through the amendment process, because it is the avenue laid out by rule. In the case of the federal New Source Review regulations, the proposed change, coupled with the emissions reductions from decommissioned equipment, makes the change “non-significant”. Such changes are the norm among permit amendments. In the case of the federal New Source Performance Standards and state performance standards, the allowable emission increases are pre-established by rule. In the case of federal National Emission Standards for Hazardous Air Pollutants, no regulations are being proposed for sewage sludge incineration. For MCES in particular, both the facility and MPCA recognized the benefits of performing an Air Toxics Review and an EAW prior to noticing the permit, even though neither review was required by law. C0MMENT 44: “y/n, have other projects of this size and potential for impacts been classified by the MPCA as “synthetic” minor modification as proposed? If yes, provide exact circumstances and scopes.” RESPONSE 44: “Synthetic minor” major permit amendments are routine. However, MPCA does not keep records of the major permit amendments that are “synthetic minors.” Attachment A to the Response to Comments is a list of major permit amendments acted on since 1996. Of the roughly 300 amendments listed, supervisors estimate that 70-95 percent are synthetic minors. (See Attachment A to the Responses to Comments.) C0MMENT 45: “What specific regulatory precedents does the MPCA have for the proposed “netting out’ of PSD/NSR non-attainment regulations?” RESPONSE 45: The “netting out” procedure is found in 40 CFR 52.21(b)(3). Examples are provided in EPA’s 1990 draft New Source Review Workshop Manual.

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Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet C0MMENT 46: “y/n, the net emission changes in Table 9 show all the pollutants as being just short of the PSD/NSR triggers? If yes, provide the MPCA records for the past actual emissions and the MPCA calculations for the potential future emissions.” RESPONSE 46: These calculations are found in the MCES permit application. The calculations are lengthy (about 100 pages), and are available for inspection at the MPCA St. Paul office. Minn R. 4410.1000, subp. 1 Purpose of an EAW states “The EAW is a brief [emphasis added] document prepared in worksheet format which is designed to rapidly assess the environmental effects which may be associated with a proposed project.” It is not the intent of an EAW to recapitulate in detail calculations required as part of a permit application. EAWs never contain as much specific detail as permit applications. C0MMENT 47: “23.4.4.3 states that National Emission Standard’s for Hazardous Air Pollutant will not apply to the new facility?” RESPONSE 47: A facility that is a major source of Hazardous Air Pollutant (HAPs) must obtain a Title V permit. No HAP (40 CFR 63) performance standards presently exist for sewage sludge incinerators, and it is not expected that any would be promulgated in the future. A HAP performance standard does apply to publicly owned treatment works that are major sources. However, this facility is not a major source and the standard therefore does not apply. C0MMENT 48: “y/n, the MPCA has independently calculated the HAP sources and pollutant levels? If yes, provided the calculations for each hazardous emission source and pollutant.” RESPONSE 48: MCES has voluntarily requested enforceable HAP performance limits to preserve its status as a minor source under Part 63. The HAP limits are based on a 12-month rolling sum, so calculations are minimal and easily evaluated. (See Attachment B to the Responses to Comments.) C0MMENT 49: “y/n, will the proposed sewage incineration operations comply with Section 129 regulations of the Clean Air Act as now written? If yes, provide the supporting data. If no, why not?” RESPONSE 49: At present, the proposed incinerators are not required to comply with Section 129, and may never be required to comply. Section 129 directs EPA to draft rules for incinerators – in particular, incinerators of municipal waste, medical waste, industrial/commercial waste, and other waste. Once these EPA rules are promulgated, the incinerators must comply with them as applicable. Sewage sludge does not appear to be regulated by Section 129. C0MMENT 50: “23.4.5 references toxic air emissions dispersion modeling conducted? Y/n, is this modeling completed? If yes, what were the specific results? If no, when will the results be obtained?” RESPONSE 50: Dispersion modeling was conducted for air toxics as part of the ATR. The ATR demonstrated that the MWWTP’s air emissions meet the Minnesota Department of Health’s (MDH) de minimis risk management guideline criteria for all residential receptors. However, the ATR indicated that acute health risks to adjacent workers exceeded the Health Department’s de minimis risk level. Therefore, an Acute Hazard Analysis was submitted as an ATR addendum. The addendum included a more refined air dispersion analysis for the acute time period. The Acute Hazard Analysis demonstrated that the impacts from the MWWTP air emissions meet the MDH risk management criteria for all worker receptors as well. In addition, the ATR demonstrated that the proposed solids processing equipment sources are not the primary risk drivers for the facility. Hydrogen sulfide (H2S) emissions from the

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Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet existing liquid treatment processes and potential solvent emissions from maintenance (painting and degreasing) activities were the major contributors to the estimated health risk from the facility emissions. These existing sources will not be modified as part of the Solids Processing Improvements Project. MCES has agreed to perform H2S monitoring to verify that the impacts from H2S emissions are not a health concern. In addition, MCES will implement a pollution prevention program for its maintenance painting activities. C0MMENT 51: “y/n, considering the proposed project’s size, cost, inaccuracy/incompleteness of information, and potential impacts that require further investigation, the preparation of an Environmental Impact Statement is prudent public policy? If no, one is hereby requested.” RESPONSE 51: Project size and expense, in and of themselves, do not necessarily or automatically require an EIS. This project, in fact, would not even require preparation of a mandatory EAW under Minn R. 4410.4300. The commentor alleges, but has not demonstrated, that the information contained in the EAW is inaccurate and incomplete. Nor has the commentor demonstrated that there are potential impacts that require further information. It is the position of the staff that an EIS is not required. Comments No. 52-55 Submitted by Thomas Balcom, Minnesota Department of Natural Resources, Letter dated March 7, 2001 COMMENT 52: “ The levels of mercury partitioned to the liquid waste stream are not detailed. Explain how the new solids processing may affect the liquid process and ultimately the receiving water.” RESPONSE 52: The amount of mercury that is recycled with spent scrubber water to the plant headworks is expected to be reduced by at least 70 percent compared to current levels. Currently, approximately 30 percent of the mercury in the multiple hearth incinerator exhaust is captured in the scrubber water and recycled to the headworks. With the new system, 70 percent or more of the mercury is expected to be captured with the dry ash. Of the remaining 30 percent, approximately 30 percent (equivalent to approximately 10 percent of the uncontrolled mercury emissions), may be captured in the wet scrubber and the wet electrostatic precipitator. This residual amount will be returned to the headworks. Mercury and phosphorous associated with the centrate solids or scum underflow solids will be recycled to the liquids treatment process. At some point the amount recycled and the amount going up the stack or out with the ash will reach equilibrium. The amount recycled in the new facility will be less than the amount currently recycled, and therefore, does not impact the ability of the plant to comply with its discharge permit. In any event, the environmental permits held by the facility require that it meet water quality effluent limits and air emission limits. If these limits are not met, the facility will face enforcement action. MCES will test and evaluate the plant effluent to ensure compliance with their National Pollutant Discharge Elimination System (NPDES) permit. In addition, the stack emissions will be tested to demonstrate compliance with their air permit. COMMENT 53: “We recommend testing and evaluation of dewatering centrate and underflow from the scum concentration tanks to establish whether pretreatment or alternate disposal is necessary for achieving the desired facility emission levels. The information collected can be referenced in the One Year Certification Report that is to be submitted to MPCA as a permit requirement.” RESPONSE 53: MCES designs and implements appropriate testing and monitoring programs as needed to manage changes in influent characteristics, process equipment modifications or replacements, and operational changes. For example, MCES conducted a pilot phosphorus monitoring program during the fall of 2000 and winter of 2001 on the centrifuge sludge. At the same time, bench scale testing was

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Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet performed to determine the feasibility of enhancing phosphorus removal with chemical addition when needed. Additional phosphorus monitoring is planned concurrent with the startup of two additional centrifuges in late 2001 and spring of 2002. The issue of phosphorus and mercury levels (and for that matter, levels of any nutrients or pollutants in the return lines from the centrifuges to the headworks of the plant is of concern to the MPCA, and will be examined during the review of plans and specifications. The MPCA will be asking MCES what levels are expected, what impact it will have on the plant and what will be done if levels exceed the expected levels. In addition, the MPCA will be questioning MCES during start-up about the actual levels occurring and what impacts they are having. Finally, the One Year Certification Report will serve as a way to document results during the start-up period. That report is required because a portion of the project is being funded by Public Facilities Authority money. No permit is required for that part of the project. The essential point here is that the facility must meet its air emission and water quality effluent limits. Exactly what fine tuning and even major revamping of process units is necessary to do that depends upon what is observed during start up operations. COMMENT 54: “Testing of the relatively small centrate sidestream is advised to confirm whether any high phosphorus concentrations are present. If phosphorus is present, it could impair ultimate effluent performance without pretreatment prior to reintroduction back into the secondary waste stream. This information can also be presented as part of the One Year Certification Report.” RESPONSE 54: See response to comment 53. COMMENT 55: “We seek clarification on the use of effluent water for the wet scrubber system. Is this chlorinated effluent at those times when chlorination is required? Can residual free chlorine or chloramine cause the formation of hazardous stack emissions through combination with reactive stack byproducts? If unchlorinated water is used, does the very short residence time assure destruction of virus, bacterial spores, and all biologicals?” RESPONSE 55: The wet scrubber uses water from the effluent channel of the plant. Under some conditions, it may be necessary to add small amounts of chlorine to control biofouling in process equipment before the water reaches the wet scrubber. The chlorine concentrations are very low. At those times when chlorination is necessary, approximately 5 mg/L of hypochlorite will be added to the plant effluent water. In comparison, up to 20 mg/L may be added for disinfection of wastewater while a typical concentration for the disinfection of drinking water is 1 mg/L. The chlorine could react with nitrogenous compounds in the effluent to form trace amounts of chloramines, which would most likely remain in the liquid stream. Any other chlorinated compounds that could possibly be formed and released in the air stream would be present in only trace amounts. The scrubber water comes in contact with the exhaust gases at a temperature of 300 degrees Fahrenheit. This temperature is high enough to ensure the destruction of biological organisms that may be present. The scrubber water volume will be less than it is currently.

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Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet Comments Nos. 56-57 Submitted by Dana Donatucci, Ph.D. Associate Administrator, U of M Waste Management and Recycling, Letter dated March 4, 2001 COMMENT 56: “My concern is that the (alkaline stabilization) equipment will not be used to any significant extent. With the small quantity of biosolids available, marketing the biosolids becomes more difficult because the supply would be erratic and inconsistent leading to the failure of land application. Has the agricultural community been approached and involved by the Met Council in these discussions in order to develop and secure markets for biosolids? What is the Met Council doing now to develop these markets? If we are investing financial resources for land applying biosolids, we should be processing closer to 50% of the biosolids for land application.” RESPONSE 56: MCES has developed a sustainable market for a product volume equivalent to 10 percent of the sludge throughput. This sludge throughput split between incineration and alkaline stabilization represents the optimum balance considering energy, environmental, and cost parameters considering the cost of building sufficient winter biosolids storage, energy required to process and transport biosolids versus energy recovery from incineration, and incineration’s lower potential for emitting odorous compounds. See also the responses to Comments 34 and 36. COMMENT 57: “The public was mislead to believe that replacing the incinerators would solve the odor problem. The 1995 MWWTP Odor Control Study – Final Report showed that a significant source of odors was from Zimpro, the process by which the sludge is dewatered prior to incineration. Replacing Zimpro with centrifuges, as is being proposed, would significantly reduce the odor problems. Replacing the incinerators was not necessary to solve the odor problem but the method of dewatering was.” RESPONSE 57: Decommissioning of the Zimpro sludge thermal conditioning process is a component of the Solids Processing Improvements Project that will greatly reduce the odors associated with the plant. The plant's neighbors residing in the Indian Mounds Park, Dayton's Bluff, and East Side neighborhoods were presented the options of replacing the existing Zimpro thermal conditioning process and multiple hearth incinerators with either fluidized bed incineration or heat drying as the primary solids processing technology. The neighbors overwhelmingly favored fluidized bed incineration because heat drying has a greater potential for creating new odors. Comments No. 58 Submitted by Sharon Anderson, Transportation Planner, Minnesota Department of Transportation, Metro Division, Letter dated February 15, 2001. COMMENT 58: “We find the assessment acceptable, as it should have little or no impact to the State Highway System or its right of way.” RESPONSE 58: None necessary. Comments No. 59 Submitted by Helen A. Boyer, Director, Environmental Services, Metropolitan Council, Letter dated March 5, 2001. COMMENT 59: “The staff review has concluded that the EAW is complete and accurate with respect to regional concerns and raises no issues of controversy with Council policies. An EIS is not necessary for regional concerns.” RESPONSE 59: None necessary.

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Metropolitan Wastewater Treatment Plant Solids Processing Responses to Comments on the St. Paul, Minnesota Environmental Assessment Worksheet

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Comments No. 60 Submitted by Larry Zangs, City of Saint Paul, E-mail dated March 7, 2001 COMMENT 60: In reviewing the EAW for this project, it appears that a city review and approval step is missing. The referenced project is located in the Saint Paul River Corridor District. Section 62.108(a)(8) of the City's Legislative Code requires Site Plan Review for any development in this district as a prerequisite to obtaining building permits for the construction. Site Plan Review is conducted by staff and takes approximately four weeks to complete. Table 1 of the EAW document listing potential permits does not mention this city review process. Tom Beach from our office is the contact on this. You may call him at (651) 266-9086. If you need to call me, my number is (651) 266-9109. RESPONSE 60: Comment Noted. The MCES has been so advised.

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