NPDES INDIVIDUAL PERMIT APPLICATION NARRATIVE
MUSCATINE EXPANSION FACILITY
Greenfield Agricultural Partners LLC 4200 Prairie Wind Drive, Suite 300 West Des Moines, Iowa 50266
Prepared by:
Calderwood & Harkness LLP 801 Grand Avenue, Suite 4400 Des Moines, Iowa 50309
Prepared on Behalf of:
Greenfield Agricultural Partners LLC 4200 Prairie Wind Drive, Suite 300 West Des Moines, Iowa 50266
Filed with:
Iowa Department of Natural Resources Water Quality Bureau 502 East 9th Street Des Moines, Iowa 50319
Date: May 5, 2023
C&H Matter Number: 1020-00004
Regulatory Authority: Iowa Administrative Code 567—Chapter 64 Clean Water Act § 402, 33 U.S.C. § 1342
Section 1: Introduction and Purpose of Application
1.1 Overview. Greenfield Agricultural Partners LLC ("GAP"), an Iowa limited liability company organized under the laws of the State of Iowa (Iowa Secretary of State Filing No. 548213; Employer Identification Number 46-3827194), hereby submits this application narrative in support of its National Pollutant Discharge Elimination System ("NPDES") Individual Permit application for the Muscatine Expansion Facility (the "MEF" or the "Facility"). This application is submitted to the Iowa Department of Natural Resources ("IDNR"), Water Quality Bureau, pursuant to Section 402 of the Clean Water Act, 33 U.S.C. § 1342, and the implementing regulations set forth in Iowa Administrative Code 567—Chapter 64.
This narrative accompanies and supplements the standard NPDES permit application forms (EPA Forms 1 and 2C) submitted concurrently herewith. The application seeks authorization for two discharge points from the MEF to Sweetland Creek, a tributary of the Mississippi River, in Muscatine County, Iowa:
• Outfall 001: Treated process wastewater, consisting of combined flows from soybean processing wash water, cooling tower blowdown, equipment washdown, floor drains, and laboratory wastes, following treatment through a multi-stage treatment system. Outfall 001 will be a continuous discharge during facility operations, with a design flow of 0.38 million gallons per day ("MGD").
• Outfall 002: Industrial stormwater, consisting of stormwater runoff from paved areas, the fertilizer loadout pad, and the truck wash area. Outfall 002 will be an intermittent discharge, occurring only during and following precipitation events, and will be managed pursuant to a comprehensive Stormwater Pollution Prevention Plan ("SWPPP").
The application is accompanied by a filing fee of $3,600, payable to the IDNR, enclosed with the application materials in accordance with the fee schedule established under Iowa Administrative Code 567—64.16.
GAP respectfully requests that the IDNR proceed with its review of this application, issue public notice in accordance with applicable regulations, and issue the requested NPDES Individual Permit on a schedule consistent with the Department's standard processing timelines. GAP is prepared to respond promptly to any requests for additional information or clarification that may arise during the review process.
1.2 Applicant Information
The applicant for this NPDES Individual Permit is Greenfield Agricultural Partners LLC, an Iowa limited liability company with its principal offices located at 4200 Prairie Wind Drive, Suite 300, West Des Moines, Iowa 50266. GAP's Employer Identification Number is 46-3827194.
GAP operates in the agriculture and specialty chemicals industry, with core business activities encompassing soybean processing, fertilizer blending, and crop-nutrient distribution across the upper Midwest region. The company was founded in 2011 by the Halverson family and has since grown into a significant regional participant in the soybean processing and agricultural input sectors. GAP currently operates three existing soybean crush facilities: two located in Iowa (Cedar Rapids and Fort Dodge) and one in Nebraska (Grand Island). In addition to its soybean processing operations, GAP distributes specialty fertilizer products across Iowa, Nebraska, Minnesota, South Dakota, and Wisconsin.
For the fiscal year ending December 31, 2022, GAP reported consolidated revenues of approximately $485 million and earnings before interest, taxes, depreciation, and amortization ("EBITDA") of approximately $62 million. The MEF represents a significant strategic investment for the company and will be GAP's fourth soybean processing facility and its first integrated soybean crush and specialty fertilizer blending operation.
The following individuals serve as key contacts for the Applicant in connection with this application:
Nils Halverson Founder & Chief Executive Officer Greenfield Agricultural Partners LLC 4200 Prairie Wind Drive, Suite 300 West Des Moines, Iowa 50266 Telephone: (515) 555-2200
Email: n.halverson@greenfieldagpartners.com
Patricia Caldwell General Counsel & Vice President of Regulatory Affairs Greenfield Agricultural Partners LLC 4200 Prairie Wind Drive, Suite 300 West Des Moines, Iowa 50266 Telephone: (515) 555-2215
Email: p.caldwell@greenfieldagpartners.com
Derek Yun Director of Environmental, Health & Safety ("EHS") Greenfield Agricultural Partners LLC 4200 Prairie Wind Drive, Suite 300 West Des Moines, Iowa 50266 Telephone: (515) 555-2240
Email: d.yun@greenfieldagpartners.com
Margaret Solberg Vice President of Operations / Muscatine Project Lead Greenfield Agricultural Partners LLC 4200 Prairie Wind Drive, Suite 300 West Des Moines, Iowa 50266 Telephone: (515) 555-2260
Email: m.solberg@greenfieldagpartners.com
Ms. Caldwell, as General Counsel and Vice President of Regulatory Affairs, has been designated as GAP's authorized representative for purposes of this NPDES permit application and has executed the certification statement required under 40 C.F.R. § 122.22, which appears at the conclusion of this narrative.
1.3 Legal Counsel
This NPDES Individual Permit Application Narrative has been prepared by Calderwood & Harkness LLP, a law firm with offices in Des Moines, Iowa. Calderwood & Harkness's environmental and natural resources practice group has extensive experience in the preparation of NPDES permit applications, water quality permitting, and Clean Water Act compliance for agricultural and industrial facilities throughout the state of Iowa and the broader Midwest region.
The following attorneys at Calderwood & Harkness LLP have been responsible for the preparation of this narrative:
Rafael Dominguez, Lead Associate Calderwood & Harkness LLP 801 Grand Avenue, Suite 4400 Des Moines, Iowa 50309 Telephone: (515) 555-7800
Email: r.dominguez@calderwoodharkness.com
Cynthia Ho, Working Associate Calderwood & Harkness LLP 801 Grand Avenue, Suite 4400 Des Moines, Iowa 50309 Telephone: (515) 555-7815
Email: c.ho@calderwoodharkness.com
James Prentice, Responsible Partner Calderwood & Harkness LLP 801 Grand Avenue, Suite 4400 Des Moines, Iowa 50309 Telephone: (515) 555-7750
Email: j.prentice@calderwoodharkness.com
All inquiries from the IDNR regarding this application may be directed to Mr. Dominguez or Mr. Prentice at the contact information provided above.
1.4 Technical Consultants
In the preparation of this application, GAP has retained two technical consulting firms with specialized expertise in environmental engineering, water quality analysis, and industrial facility design. The contributions of each firm are described below.
Pinnacle Environmental Consultants Inc. ("Pinnacle"), an Iowa corporation with offices at 1120 Ingersoll Avenue, Suite 210, Des Moines, Iowa 50309, was retained to perform the process wastewater characterization study, develop the expected raw wastewater quality parameters for the MEF based on data from comparable soybean processing and fertilizer blending facilities, and prepare the Stormwater Pollution Prevention Plan. The Senior Water Quality Scientist responsible for this work is Karen Ott. Ms. Ott has over eighteen years of experience in industrial wastewater characterization and NPDES permitting for agricultural processing facilities in Iowa and throughout the Midwest. Pinnacle's process wastewater characterization study is appended to this application as Appendix D, and the SWPPP is appended as Appendix F.
Ridgeline Engineering Group LLC ("Ridgeline"), a Nebraska limited liability company with offices at 7700 Pioneers Boulevard, Suite 105, Lincoln, Nebraska 68506, was retained to provide facility process and civil engineering design services for the MEF. Ridgeline's scope of work includes the preparation of process flow diagrams, mass-balance data, treatment system design drawings and specifications, and stormwater management plans for the facility. The Project Manager for this engagement is Thomas Novak, P.E. Mr. Novak is a licensed professional engineer in both Iowa and Nebraska and has served as lead engineer on several comparable soybean processing and agricultural chemical facility projects throughout the region. Ridgeline's process flow diagrams and mass-balance data are appended as Appendix C, and the treatment system design drawings and specifications are appended as Appendix E.
The technical data and analyses prepared by Pinnacle and Ridgeline form the engineering and scientific foundation for the discharge characterizations, treatment system descriptions, and proposed effluent limitations set forth in this narrative. GAP, Pinnacle, and Ridgeline are available to provide additional technical information or clarification as may be requested by the IDNR during its review of this application.
Section 2: Facility Description
2.1 Project Overview
The Muscatine Expansion Facility is a new greenfield soybean processing and specialty fertilizer blending facility to be constructed by GAP on a 147-acre site in Muscatine County, Iowa. The MEF represents a significant expansion of GAP's existing operations and will be the company's first fully integrated soybean crush and specialty fertilizer blending facility.
The planned production capacity of the MEF is as follows:
• Soybean Crush Capacity: 3,200 tons per day of raw soybeans, producing soybean oil and soybean meal as primary products.
• Granular Fertilizer Blending Line: 450 tons per day of granular fertilizer blending capacity, producing specialty crop-nutrient products for distribution across the upper Midwest.
The total estimated capital cost for the MEF is $178 million, encompassing all site preparation, facility construction, process equipment installation, wastewater treatment infrastructure, stormwater management systems, utility connections, and ancillary support facilities. The project is being financed through a combination of equity contributions from GAP's existing ownership group and a senior secured term facility, as further described in Section 9 of this narrative.
The MEF is expected to create approximately 145 full-time positions upon commencement of operations, including process operators, maintenance technicians, administrative staff, and environmental compliance personnel. GAP anticipates that the facility will also generate significant indirect employment and economic activity in Muscatine County and the surrounding region.
2.2 Site Location and Description
The proposed site for the MEF is located at 14800 Highway 61 North, Muscatine, Iowa 52761, in Muscatine County. The site is identified by Muscatine County Parcel Identification Number 0735-19-200-004.
The site comprises a total of 147 acres situated along the west side of U.S. Highway 61, approximately four miles north of the City of Muscatine. The property is generally flat to gently rolling terrain, with elevations ranging from approximately 580 to 595 feet above mean sea level. Historically, the site has been used for row-crop agriculture, principally corn and soybean production. The site is bordered to the north and west by active agricultural land, to the east by U.S. Highway 61, and to the south by a mix of agricultural land and rural residential properties.
GAP acquired the site from the Reinholt Family Trust on January 20, 2023, for a purchase price of $3,820,000, representing approximately $25,986 per acre. The title search and closing were handled by Hawkeye Title & Escrow LLC, 220 West 2nd Street, Muscatine, Iowa 52761. Documentation of the title transfer and site ownership is included in Appendix I to this application.
The site is served by adequate transportation infrastructure, including direct access to U.S. Highway 61 and proximity to the Vireo Enterprises Railway right-of-way. Municipal water service will be extended to the site from the City of Muscatine's water distribution system pursuant to a water service agreement currently under negotiation. Natural gas service will be provided by Harborview Corporation. Electrical service will be provided by Vireo Holdings.
A detailed site map and outfall location map, prepared by Ridgeline Engineering Group LLC, are included as Appendix B to this application.
2.3 Zoning and Local Approvals
The 147-acre site is designated as Agricultural-Industrial ("AI") under the Muscatine County zoning ordinance. The AI zoning designation permits agricultural processing and industrial uses subject to the issuance of a conditional use permit by the Muscatine County Board of Supervisors.
GAP applied for a Conditional Use Permit ("CUP") for the MEF in October 2022. Following a public hearing held on November 8, 2022, the Muscatine County Board of Supervisors approved CUP No. MC-2022-041 on November 15, 2022, authorizing the construction and operation of the soybean processing and specialty fertilizer blending facility at the site. The CUP approval was conditioned upon GAP's compliance with all applicable federal, state, and local environmental permit requirements, including the NPDES permit that is the subject of this application.
A complete copy of CUP No. MC-2022-041, including the Board of Supervisors' resolution and all conditions of approval, is included as Appendix A to this application.
No variances, special exceptions, or other land use approvals were required for the MEF beyond the CUP.
2.4 Process Description
The MEF will incorporate the following principal process operations:
Soybean Receiving, Cleaning, and Storage. Raw soybeans will be received at the facility by truck and rail. Upon arrival, soybeans will be weighed, sampled for quality, and transferred to storage silos with a combined capacity of approximately 2.4 million bushels. Prior to processing, soybeans will be cleaned to remove foreign materials, including dirt, stones, and plant debris, using scalpers, screeners, and destoners. Wash water generated during the cleaning process constitutes a process wastewater source addressed in this application.
Soybean Crushing and Oil Extraction. Cleaned soybeans will be cracked, conditioned, and flaked before being processed through a solvent extraction system to separate soybean oil from soybean meal. The crushing and extraction operations will have a design capacity of 3,200 tons per day of raw soybeans. Hexane will be used as the extraction solvent; the hexane recovery and solvent management system is addressed in the PSD air permit application referenced in Section 2.5 below. Process wastewater associated with the crushing and extraction operations includes equipment washdown water and floor drain discharges from the processing areas.
Soybean Meal Drying and Handling. Following oil extraction, the de-oiled soybean flakes will be dried, cooled, and processed into soybean meal for sale as animal feed. The meal drying and handling operations generate minimal process wastewater; however, equipment washdown and floor drain discharges from these areas are included in the combined process wastewater flow.
Specialty Fertilizer Granulation and Blending. The MEF will include a 450-ton-per-day specialty fertilizer granulation and blending line. Raw fertilizer materials, including urea, diammonium phosphate, potash, and micronutrient additives, will be received, stored, and blended into custom granular fertilizer formulations. The blending line includes granulation, screening, coating, and packaging operations. Stormwater runoff from the fertilizer loadout pad constitutes an industrial stormwater source addressed at Outfall 002.
Product Storage and Loadout Operations. Finished soybean oil, soybean meal, and fertilizer products will be stored on-site in dedicated storage facilities and loaded for outbound shipment by truck and rail. The loadout areas, including paved truck staging and loading pads, are potential sources of industrial stormwater addressed in this application.
Detailed process flow diagrams and mass-balance data for all of the above operations, prepared by Ridgeline Engineering Group LLC under the direction of Thomas Novak, P.E., are included as Appendix C to this application.
2.5 Related Permits
In addition to the NPDES Individual Permit that is the subject of this application, the MEF is subject to the following permits and approvals:
Prevention of Significant Deterioration (PSD) Construction Permit. GAP filed a PSD Construction Permit application with the IDNR Air Quality Bureau on April 28, 2023, for the MEF. The PSD application addresses emissions of criteria pollutants and hazardous air pollutants from the soybean processing, meal drying, fertilizer blending, and associated combustion sources at the facility. Of particular relevance to this NPDES application, the cooling tower unit (designated EU-06 in the air permit application) is addressed in both the PSD application (with respect to particulate matter drift emissions) and this NPDES application (with respect to cooling tower blowdown discharge). The PSD permit application is pending before the IDNR Air Quality Bureau in a separate proceeding.
Conditional Use Permit No. MC-2022-041. As described in Section 2.3 above, the Muscatine County Board of Supervisors approved this CUP on November 15, 2022, authorizing the construction and operation of the MEF at the site.
GAP is not aware of any other federal, state, or local permits or approvals required for the MEF that have not been applied for or obtained as of the date of this narrative. GAP will apply for all additional permits and approvals as they are identified during the course of facility design and construction.
Section 3: Wastewater Sources and Characterization
3.1 Process Wastewater Sources
The MEF will generate process wastewater from several distinct sources within the facility. All process wastewater streams will be combined and routed to the on-site wastewater treatment system for treatment prior to discharge through Outfall 001. The principal process wastewater sources are described below.
Soybean Wash Water. The soybean receiving and cleaning operations will generate wash water containing suspended solids (dirt, soybean hull fragments, and plant debris), organic matter, and trace quantities of oils and greases associated with the soybean material. Soybean wash water is expected to represent the largest single process wastewater stream by volume. Based on the design throughput of 3,200 tons per day of raw soybeans and wash water usage rates observed at comparable soybean processing facilities, the soybean wash water flow is estimated at approximately 0.15 MGD. This stream will be characterized by relatively high total suspended solids ("TSS") concentrations and moderate five-day biochemical oxygen demand ("BOD₅") levels.
Cooling Tower Blowdown. The MEF will operate a two-cell cooling tower system (designated EU-06 in the PSD air permit application) with a combined recirculating flow of approximately 18,000 gallons per minute. The cooling towers will provide process cooling for the soybean oil extraction and meal drying operations. To maintain acceptable water quality within the recirculating cooling water system and to prevent scaling and corrosion, a portion of the recirculating water must be continuously discharged as blowdown. The cooling tower blowdown stream will contain elevated concentrations of dissolved solids (principally calcium, magnesium, sulfate, and chloride), as well as residual biocides (oxidizing and non-oxidizing) and anti-scaling agents used in the cooling water treatment program. The estimated cooling tower blowdown flow rate is approximately 0.10 MGD, based on a design cycles-of-concentration ratio of 5.0.
Additional Process Water Streams. The following additional process water streams will be generated at the MEF and will be combined with the soybean wash water and cooling tower blowdown for treatment:
• Equipment washdown water: Generated from periodic cleaning and washdown of processing equipment, conveyors, tanks, and piping in the soybean crush, oil extraction, meal handling, and fertilizer blending areas.
• Floor drain discharges: Floor drains in the soybean processing, oil extraction, and fertilizer blending buildings will collect incidental spills, washdown water, and accumulated liquids from the processing areas.
• Laboratory wastes: The MEF will include an on-site quality control laboratory that will generate small volumes of laboratory wastewater from analytical testing of soybean, oil, meal, and fertilizer product samples. Laboratory wastes will be pre-screened to ensure that no hazardous wastes or incompatible materials are introduced into the process wastewater treatment system.
Combined Design Flow. The combined design flow for all process wastewater sources routed to the on-site treatment system and discharged through Outfall 001 is 0.38 MGD. This design flow represents the maximum anticipated daily average flow under full production conditions and includes a reasonable contingency factor to account for flow variability associated with batch processing operations, seasonal production changes, and periodic equipment cleaning events.
3.2 Process Wastewater Characterization
A comprehensive process wastewater characterization study was prepared by Pinnacle Environmental Consultants Inc. under the direction of Karen Ott, Senior Water Quality Scientist. The characterization study is based on sampling and analytical data obtained from GAP's three existing soybean crush facilities (Cedar Rapids, Fort Dodge, and Grand Island), supplemented by published data from comparable soybean processing and fertilizer blending operations throughout the Midwest.
Because the MEF is a new greenfield facility that has not yet commenced operations, actual process wastewater samples from the MEF are not available. Accordingly, the characterization study employs a conservative approach, using the upper-range values observed at comparable facilities as the basis for estimating raw wastewater quality prior to treatment. This approach ensures that the proposed treatment system is designed with adequate capacity and that the proposed effluent limits are achievable under worst-case conditions.
The following table summarizes the expected raw wastewater quality parameters for the combined process wastewater stream prior to treatment:
The full characterization report, including the detailed analytical data from comparable facilities, statistical analyses, and the methodology employed in developing the estimated ranges, is included as Appendix D to this application. Pinnacle and GAP are available to provide additional data or analysis as may be requested by the IDNR during its review.
3.3 Stormwater Sources
In addition to the process wastewater sources described above, the MEF will generate industrial stormwater runoff from several areas of the facility. These stormwater sources will be discharged through Outfall 002 and will be managed in accordance with the Stormwater Pollution Prevention Plan prepared by Pinnacle Environmental Consultants Inc.
The principal industrial stormwater sources at the MEF include:
• Stormwater runoff from paved areas surrounding process buildings: The MEF will include approximately 18 acres of paved surfaces, including parking lots, truck staging areas, and access roads surrounding the soybean processing and fertilizer blending buildings. Stormwater from these areas may contain trace quantities of petroleum hydrocarbons, suspended solids, and other pollutants associated with vehicle traffic and outdoor material handling.
• Stormwater from the fertilizer loadout pad: The fertilizer loadout pad will be a paved, outdoor area used for loading granular fertilizer products into trucks for distribution. Stormwater runoff from this area has the potential to contain nutrient-laden residues, including nitrogen and phosphorus compounds, from incidental spillage during loadout operations. This source is of particular significance and is addressed through dedicated best management practices in the SWPPP.
• Truck wash area drainage: The MEF will include a covered truck wash station for cleaning delivery and transport vehicles. Drainage from the truck wash area will be collected and routed through an oil-water separator before discharge. During significant precipitation events, stormwater may also enter the truck wash drainage system.
All industrial stormwater discharges from the MEF will be intermittent in nature, occurring only during and following precipitation events. Discharge volumes will be dependent on the intensity, duration, and frequency of rainfall events at the site. Because these stormwater flows are storm-event driven and distinct from the continuous process wastewater discharge, they are addressed separately as Outfall 002.
The SWPPP, which details the structural and non-structural best management practices to be implemented for stormwater management at the MEF, is included as Appendix F to this application.
Section 4: Receiving Water Characterization
4.1 Receiving Water Identification
The proposed receiving water for both Outfall 001 (treated process wastewater) and Outfall 002 (industrial stormwater) is Sweetland Creek, a perennial stream located in Muscatine County, Iowa. Sweetland Creek originates approximately seven miles northwest of the MEF site, flows generally southeastward through agricultural and rural residential areas of Muscatine County, and discharges into the Mississippi River approximately 3.8 miles downstream of the proposed outfall locations.
The proposed discharge points for Outfall 001 and Outfall 002 are located on the western bank of Sweetland Creek at the eastern boundary of the MEF site. The specific coordinates and locations of the outfall structures are depicted on the Outfall Location Map prepared by Ridgeline Engineering Group LLC and included as Appendix B to this application. The discharge points are positioned along a reach of Sweetland Creek characterized by a moderate gradient, a predominantly sand and gravel substrate, and forested riparian buffers along both banks.
Sweetland Creek at the point of discharge has an estimated drainage area of approximately 14 square miles. The channel width at the proposed discharge location is approximately 15 to 20 feet during normal flow conditions, with a bankfull width of approximately 30 feet.
4.2 Iowa DNR Water Quality Classifications
Sweetland Creek, at and downstream of the proposed discharge points, has been assigned the following designated use classifications by the IDNR pursuant to Iowa Administrative Code 567—Chapter 61:
• Class A1 — Primary Contact Recreation: This classification designates waters in which recreational activities involving prolonged and direct contact with the water, such as swimming, water skiing, and similar activities, may occur. Waters designated as Class A1 are subject to bacteriological water quality criteria, including a fecal coliform standard of 200 colony-forming units ("CFU") per 100 milliliters as a monthly geometric mean during the recreation season (March 15 through November 15).
• Class B(WW) — Warm Water Aquatic Life: This classification designates waters capable of supporting and maintaining a balanced, integrated, adaptive community of warm water fish and other aquatic organisms. Waters designated as Class B(WW) are subject to water quality criteria for ammonia-nitrogen, dissolved oxygen, temperature, and other parameters necessary to protect warm water aquatic life.
These designated use classifications are the basis for the water quality-based effluent limitations proposed in Section 7 of this narrative.
4.3 Receiving Water Quality
Existing ambient water quality data for Sweetland Creek are available from the IDNR's ambient water quality monitoring network and from periodic monitoring studies conducted by the Muscatine County Soil and Water Conservation District. A compilation of available ambient water quality data for the reach of Sweetland Creek at and downstream of the proposed discharge points is included as Appendix H to this application.
Based on the available data, Sweetland Creek generally exhibits water quality conditions consistent with its designated uses. Dissolved oxygen concentrations have historically met or exceeded the Class B(WW) criterion of 5.0 mg/L, and ammonia-nitrogen concentrations are generally low during the growing season. The stream experiences elevated turbidity and suspended sediment concentrations during spring runoff and significant precipitation events, which is characteristic of streams in agricultural watersheds in eastern Iowa.
Sweetland Creek exhibits seasonal flow variability typical of streams in the eastern Iowa landscape. Baseflow during late summer and early fall is estimated at approximately 3.5 to 5.0 cubic feet per second ("cfs"), while spring flows commonly exceed 50 cfs during snowmelt and major rainfall events. The 7-day, 10-year low flow ("7Q10") for Sweetland Creek at the proposed discharge location is estimated at approximately 1.8 cfs, based on regression analyses performed by Pinnacle Environmental Consultants using USGS regional flow data and site-specific drainage area.
As of the date of this application, Sweetland Creek is not listed on Iowa's current Section 303(d) list of impaired waters for the reach at or downstream of the proposed discharge points. The creek is not subject to any approved or pending Total Maximum Daily Load ("TMDL") analyses. The most recent Iowa Integrated Report (2022) identifies Sweetland Creek as "supporting" its designated uses for both primary contact recreation and warm water aquatic life.
The confluence of Sweetland Creek with the Mississippi River is located approximately 3.8 miles downstream of the proposed discharge points. The Mississippi River at this location is designated for multiple uses, including Class A1 (Primary Contact Recreation), Class B(WW) (Warm Water Aquatic Life), and Class C (Drinking Water). The proposed discharge from the MEF, following treatment, is not anticipated to have any measurable impact on water quality in the Mississippi River given the significant dilution available at the confluence.
4.4 Nearest Sensitive Receptors
The nearest residence to the proposed MEF site is located approximately 0.42 miles (2,218 feet) east-northeast of the facility, on the east side of U.S. Highway 61. This residence was also identified as the nearest sensitive receptor in the PSD air permit application filed on April 28, 2023. No residential structures are located between the MEF site and the proposed discharge points on Sweetland Creek.
GAP is not aware of any downstream water users with known surface water intake structures on Sweetland Creek between the proposed discharge points and the creek's confluence with the Mississippi River. There are no known municipal water supply intakes on Sweetland Creek. Agricultural irrigation in the Sweetland Creek watershed is predominantly sourced from groundwater wells rather than surface water withdrawals.
The nearest public water supply intake on the Mississippi River downstream of the Sweetland Creek confluence is operated by the City of Muscatine, located approximately 6.2 river miles downstream. Given the extensive dilution and treatment provided by both the MEF's wastewater treatment system and the natural assimilative capacity of Sweetland Creek and the Mississippi River, the proposed discharge is not anticipated to affect the City of Muscatine's drinking water supply or any other downstream sensitive receptors.
Section 5: Discharge Points — Outfall Descriptions
5.1 Outfall 001 — Treated Process Wastewater
Outfall 001 will serve as the discharge point for all treated process wastewater from the MEF. The characteristics of Outfall 001 are summarized below:
Discharge Type: Continuous during facility operations. The facility is expected to operate approximately 345 days per year, with approximately 20 days of scheduled downtime for maintenance and seasonal adjustments. During scheduled and unscheduled facility shutdowns, the discharge flow will be reduced or temporarily suspended.
Design Flow: 0.38 MGD (maximum daily average flow under full production conditions).
Sources: Combined treated effluent from the on-site wastewater treatment system, which receives and treats all process wastewater generated at the MEF, including soybean wash water, cooling tower blowdown, equipment washdown, floor drain discharges, and laboratory wastes.
Discharge Location: Outfall 001 will be located on the western bank of Sweetland Creek at a point approximately 1,450 feet east of the eastern boundary of the MEF process building complex. The approximate coordinates of the outfall are Latitude 41.4728° N, Longitude 91.0015° W (WGS 84 datum). The precise coordinates and outfall location are depicted on the Outfall Location Map included as Appendix B.
Outfall Structure: The outfall structure will consist of a 12-inch diameter Schedule 40 polyvinyl chloride ("PVC") pipe terminating in a concrete headwall with a flared-end section and riprap erosion protection at the point of discharge. The pipe invert elevation will be set at or slightly above the normal water surface elevation of Sweetland Creek to prevent backflow during normal flow conditions. A flap valve will be installed to prevent backflow during elevated stream conditions.
Monitoring Point: A dedicated monitoring point (designated Monitoring Point 001A) will be installed in the treated effluent pipe immediately upstream of the outfall structure, within the outfall manhole. The monitoring point will include provisions for the collection of representative grab and composite samples and for the installation of a flow measurement device (magnetic flowmeter). All self-monitoring samples required by the permit will be collected at Monitoring Point 001A.
5.2 Outfall 002 — Industrial Stormwater
Outfall 002 will serve as the discharge point for industrial stormwater from the MEF. The characteristics of Outfall 002 are summarized below:
Discharge Type: Intermittent, storm-event driven. Discharges through Outfall 002 will occur only during and following precipitation events of sufficient magnitude to generate stormwater runoff from the contributing drainage areas at the MEF.
Sources: Stormwater runoff from paved areas surrounding process buildings, the fertilizer loadout pad, and the truck wash area. All stormwater from these areas will be collected by the facility's stormwater conveyance system and routed to Outfall 002 through a series of stormwater inlets, pipes, sediment basins, and vegetated swales, as detailed in the SWPPP (Appendix F).
Discharge Location: Outfall 002 will be located on the western bank of Sweetland Creek at a point approximately 850 feet south of Outfall 001. The approximate coordinates of Outfall 002 are Latitude 41.4720° N, Longitude 91.0012° W (WGS 84 datum). The precise coordinates and location are depicted on the Outfall Location Map included as Appendix B.
Outfall Structure: The outfall structure will consist of a 24-inch diameter reinforced concrete pipe terminating in a concrete headwall with riprap erosion protection. The larger pipe diameter is necessary to accommodate peak stormwater flow rates during design storm events.
Best Management Practices: Stormwater discharges through Outfall 002 will be managed in accordance with the SWPPP prepared by Pinnacle Environmental Consultants Inc. The SWPPP identifies structural and non-structural BMPs designed to minimize the discharge of pollutants in stormwater, including sediment basins, vegetated swales, containment berms around the fertilizer loadout pad, and a covered truck wash area equipped with an oil-water separator. The full SWPPP is included as Appendix F, and the principal BMPs are summarized in Section 6.6 of this narrative.
Section 6: Wastewater Treatment System Design
6.1 Treatment System Overview
The MEF wastewater treatment system has been designed to treat the combined process wastewater flow of 0.38 MGD from all process wastewater sources identified in Section 3.1 of this narrative. The treatment system will produce a treated effluent suitable for discharge through Outfall 001 that meets or exceeds the proposed effluent limitations set forth in Section 7 of this narrative.
The treatment system employs a sequential, multi-stage treatment train consisting of the following unit processes:
1. Equalization Basin — Flow and load equalization to dampen peak flows and concentration variations associated with batch processing operations.
2. Dissolved Air Flotation (DAF) Unit — Physical-chemical separation of oils, greases, and suspended solids from the equalized wastewater.
3. Aerated Lagoon System (Three-Cell) — Biological treatment for BOD₅ removal, nitrification of ammonia-nitrogen, and additional settling and polishing.
4. UV Disinfection System — Ultraviolet disinfection for reduction of fecal coliform bacteria to meet Class A1 bacteriological criteria.
5. Outfall 001 — Discharge of treated effluent to Sweetland Creek.
The treatment system was designed by Ridgeline Engineering Group LLC under the direction of Thomas Novak, P.E., with wastewater characterization inputs provided by Pinnacle Environmental Consultants Inc. The treatment system design drawings and specifications are included as Appendix E, and the process flow diagrams and mass-balance data are included as Appendix C. The design incorporates conservative sizing criteria and redundancy provisions to ensure reliable performance under the full range of anticipated operating conditions, including seasonal temperature variations, peak loading events, and equipment maintenance periods.
6.2 Equalization Basin
The equalization basin is the first unit process in the treatment train and serves to dampen variations in wastewater flow rate and pollutant concentrations that result from the batch nature of certain processing operations at the MEF, particularly soybean cleaning, equipment washdown, and periodic cooling tower blowdown events.
Design Capacity: The equalization basin has been designed with an effective volume of approximately 380,000 gallons, providing approximately 24 hours of hydraulic retention time at the design flow of 0.38 MGD. This retention time is sufficient to equalize flow and load variations over a 24-hour operating cycle and to provide surge capacity for peak flow events.
Construction: The equalization basin will be an in-ground, concrete-lined structure with a minimum freeboard of two feet above the maximum operating water level. The basin will be equipped with submersible mixers to prevent solids settling and to maintain homogeneous conditions throughout the basin volume. The basin will include level instrumentation and automated flow control to regulate the feed rate to the downstream DAF unit.
Operation: Influent wastewater from the facility's process wastewater collection system will be received at the equalization basin continuously during facility operations. The submersible mixers will operate continuously to maintain the wastewater in a well-mixed condition. Effluent from the equalization basin will be pumped to the DAF unit at a controlled, uniform flow rate using variable-frequency-drive-equipped centrifugal pumps.
6.3 Dissolved Air Flotation (DAF) Unit
The DAF unit is the second unit process in the treatment train and is designed for the removal of oils, greases, and suspended solids from the equalized process wastewater.
Purpose: The DAF unit serves as the primary physical-chemical treatment step for the removal of emulsified and free oils and greases generated by the soybean processing operations, as well as for the reduction of suspended solids. The DAF unit will significantly reduce the oil and grease and TSS loading to the downstream aerated lagoon system, thereby protecting the biological treatment process and improving overall treatment system performance.
Design Parameters:
• Hydraulic loading rate: 2.5 gallons per minute per square foot (gpm/ft²) at design flow.
• Solids loading rate: 1.0 pounds per square foot per hour (lb/ft²/hr) at design loading.
• Air-to-solids ratio: 0.03 to 0.05 (by weight), optimized during commissioning.
• Recycle ratio: Approximately 30% of the DAF effluent will be recycled and pressurized for air saturation.
Chemical Addition: A coagulant (aluminum sulfate or polyaluminum chloride) and a polymer flocculant will be added upstream of the DAF unit to enhance floc formation and improve separation efficiency. Chemical dosing rates will be optimized during the commissioning period based on jar testing of actual wastewater and operational experience.
Expected Removal Efficiencies:
• Oil & Grease: Greater than 90% removal, reducing effluent oil and grease concentrations to less than 15 mg/L.
• TSS: Greater than 80% removal, reducing effluent TSS concentrations to less than 100 mg/L.
Solids Handling: Skimmed float (containing oils, greases, and solids) will be removed from the DAF unit surface by a mechanical skimmer and collected in a float sludge holding tank. The float sludge will be dewatered and disposed of or recycled in accordance with applicable solid waste management requirements.
6.4 Aerated Lagoon System
The aerated lagoon system is the biological treatment component of the treatment train and is designed for the removal of BOD₅, nitrification of ammonia-nitrogen, and further reduction of TSS through biological settling and polishing.
Configuration: The aerated lagoon system consists of three cells operating in series:
• Cell 1 — Primary Aeration and BOD₅ Removal
• Cell 2 — Secondary Aeration and Nitrification
• Cell 3 — Settling and Polishing
Total Surface Area: The three cells have a combined surface area of approximately 4.2 acres, with individual cell surface areas of approximately 1.6 acres (Cell 1), 1.4 acres (Cell 2), and 1.2 acres (Cell 3).
Hydraulic Retention Time: The total hydraulic retention time through the three-cell system at the design flow of 0.38 MGD is 18 days. This extended retention time provides ample contact time for biological oxidation of BOD₅, nitrification of ammonia-nitrogen, and gravitational settling of biological solids.
Aeration System: Cells 1 and 2 will be equipped with diffused aeration systems consisting of fine-bubble membrane diffusers mounted on the lagoon floor, supplied by positive-displacement blowers. Cell 1 will receive a higher aeration rate to support the primary BOD₅ oxidation step, while Cell 2 will be operated at a moderate aeration rate optimized for nitrification of ammonia-nitrogen. Cell 3 will not be actively aerated and will function primarily as a quiescent settling and polishing cell.
Cell-by-Cell Description:
Cell 1 — Primary Aeration and BOD₅ Removal: Cell 1 is the primary biological treatment cell, designed to achieve the majority of BOD₅ removal through aerobic biological oxidation. The cell will be operated at a dissolved oxygen concentration of 2.0 to 4.0 mg/L. The design BOD₅ loading rate is based on conservative criteria for aerated lagoon systems operating in the upper Midwest, accounting for reduced biological activity during cold weather months. Expected BOD₅ removal in Cell 1 is approximately 80 to 85%.
Cell 2 — Secondary Aeration and Nitrification: Cell 2 is designed to provide additional BOD₅ removal and, more importantly, to achieve nitrification of ammonia-nitrogen. Nitrification is the biological oxidation of ammonia (NH₃) to nitrite (NO₂⁻) and subsequently to nitrate (NO₃⁻) by autotrophic nitrifying bacteria. The cell will be operated at a dissolved oxygen concentration of 3.0 to 5.0 mg/L to support the oxygen demands of the nitrifying bacteria. The design of Cell 2 accounts for the temperature-dependent kinetics of nitrification, with the most challenging conditions occurring during the cold weather months (November through March) when water temperatures in the lagoon may drop to approximately 35 to 40°F. The seasonal ammonia-nitrogen limits proposed in Section 7 reflect these temperature-dependent kinetics, with a more stringent limit of 3.5 mg/L during the warm season (April through October) when nitrification rates are higher, and a relaxed limit of 8.0 mg/L during the cold season (November through March).
Cell 3 — Settling and Polishing: Cell 3 is a quiescent settling and polishing cell designed to achieve additional TSS removal through gravitational settling of biological solids (biosolids) generated in Cells 1 and 2. The cell will also provide additional BOD₅ polishing and some ammonia removal through endogenous respiration. Accumulated biosolids in Cell 3 will be periodically removed and disposed of in accordance with applicable regulations.
Lagoon Construction: All three cells will be constructed with compacted clay liners meeting the Iowa DNR's minimum requirements for lagoon liner systems, with a minimum clay liner thickness of 12 inches and a maximum in-place hydraulic conductivity of 1 x 10⁻⁷ cm/sec. The lagoon embankments will be constructed to provide a minimum of three feet of freeboard above the maximum operating water level.
6.5 UV Disinfection System
The UV disinfection system is the final unit process in the treatment train prior to discharge through Outfall 001.
Purpose: The UV disinfection system is designed to reduce fecal coliform bacteria in the treated effluent to meet the 200 CFU/100 mL monthly geometric mean limit required by the Class A1 (Primary Contact Recreation) designation of Sweetland Creek.
Design Capacity: The UV system is designed to treat the full design flow of 0.38 MGD.
UV Dose: The system is designed to deliver a minimum UV dose of 30 millijoules per square centimeter (mJ/cm²) at the design flow rate and at a UV transmittance of 65% (conservatively estimated for the lagoon effluent). This UV dose is consistent with established design standards for fecal coliform disinfection in wastewater applications.
Lamp Configuration: The UV system will consist of a closed-vessel, medium-pressure UV reactor housing multiple UV lamps arranged in a cross-flow configuration. The system will include automatic intensity monitoring, lamp-out alarm capabilities, and automated lamp cleaning mechanisms.
Backup and Redundancy: The UV system will include a minimum of one redundant UV reactor (duty/standby configuration) to allow for continuous operation during lamp replacement, reactor cleaning, or equipment maintenance. In the event of a UV system failure, a manual bypass with chemical disinfection capability (sodium hypochlorite) will be available as an emergency backup, subject to IDNR notification and approval.
6.6 Stormwater Management — Outfall 002
Stormwater discharges from the MEF will be managed in accordance with a comprehensive Stormwater Pollution Prevention Plan prepared by Pinnacle Environmental Consultants Inc. The SWPPP identifies the potential sources of stormwater pollutants at the MEF and prescribes structural and non-structural best management practices to minimize the discharge of pollutants in stormwater through Outfall 002. The full SWPPP is included as Appendix F to this application.
The key BMPs incorporated into the MEF stormwater management system include:
• Sediment Basins: Two sediment basins will be constructed in the stormwater conveyance system upstream of Outfall 002 to capture and retain sediment from stormwater runoff before discharge. The basins are sized to capture the first 0.5 inch of runoff from the contributing drainage areas.
• Vegetated Swales: Vegetated swales lined with native grass species will be used to convey stormwater from paved areas to the sediment basins, providing additional filtration and pollutant attenuation through sheet flow over vegetated surfaces.
• Containment Berms Around Fertilizer Loadout Pad: The fertilizer loadout pad will be surrounded by six-inch curbed containment berms designed to contain and collect stormwater runoff that may come into contact with fertilizer materials during loadout operations. Collected runoff from the loadout pad will be routed to a dedicated stormwater collection sump and directed to the sediment basins prior to discharge.
• Covered Truck Wash Area with Oil-Water Separator: The truck wash station will be located under a covered structure to minimize the volume of stormwater that enters the wash area drainage system. Drainage from the truck wash station will be routed through an oil-water separator to remove petroleum hydrocarbons and suspended solids before discharge.
• Good Housekeeping Practices: The SWPPP prescribes standard good housekeeping practices, including prompt cleanup of spills, regular sweeping of paved areas, proper storage and containment of materials, and employee training on stormwater pollution prevention.
Monitoring and Inspection Requirements: The SWPPP includes a monitoring and inspection program that requires quarterly visual inspections of all stormwater BMPs and drainage areas, semi-annual analytical sampling of stormwater discharges during qualifying storm events, and annual comprehensive SWPPP reviews and updates. Inspection and monitoring records will be maintained on-site and made available to the IDNR upon request.
Section 7: Proposed Effluent Limits
7.1 Basis for Proposed Limits
The proposed effluent limitations for Outfall 001 have been developed based on the following considerations: