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HomeMy WebLinkAboutDWQ-2025-003266 Mango II-Milford Sludge Disposal and Farm Closure Plan March 25, 2025 Mango II-Milford Table of Contents Section Page 1.0 General 3 1.1 Routine Sludge Removal 3 1.2 Farm Closure 3 1.3 Option Selection…………………………………………… 3 1.4 Scheduling of Disposal Operations 3 2.0 Projected Annual Disposal Quantities 4 3.0 Routine Removal Options 4 3.1 General 4 3.2 Sludge Drying 4 4.0 Farm Closure 6 4.1 In-Situ Management 6 4.1.1 Requirements for In-Situ management of Sludge and permit closure ………………………………………………6 4.1.2 Justification for long term in-situ management of sludge and permit closure…………………………………7 4.2 Other Waste Handling Facilities Abandonment 8 5.0 Sludge Monitoring 9 5.1 Monitoring Schedule & Methodology 9 5.2 Sludge Sampling and Testing 9 5.3 Reporting 9 GENERAL This plan identifies disposal options for lagoon sludge for on-going farm operation, and farm closure scenarios for all Mango II-Milford farm sites, and, as well as abandonment practices for lagoon and/or farm closure. Routine Sludge Removal Mango II-Milford currently owns numerous agricultural properties in Beaver, Iron, and Millard Counties, which have historically operated as hog farms. Each of these propertyies contains at least one primary treatment lagoon or digester and one secondary treatment lagoon/evaporation basin. It has and will be necessary to dispose of accumulated solids on a routine basis for continued operation. Each primary treatment lagoon has approximately 1/3 of the total lagoon volume dedicated to solids accumulation. Over time, accumulation will continue until the storage capacity is reached. The principal utilization option presented in this plan is to land apply the solids at agronomic rates onto agricultural crop land after it has been dried within engineered drying pads. The target is to dispose of solids at 100% of design storage volume. However, disposal may occur for any accumulation amount up to 120 percent of design storage accumulation. Farm Closure Should Mango II-Milford discontinue operations at any farm or totally discontinue operations altogether, it will be necessary to close down the waste handling systems and to properly address the remaining liquid. Sludge Management In-situ management of the sludge is the preferred method of managing the remaining sludge after site closure. Land application/sludge removal in compliance with the Manure Drying Plan (included in section 3.2 of this document) is the preferred method for periodic removal of solids during operation and the optional removal of solids post-closure. Scheduling of Disposal Operations Actual accumulation rates and volumes to be disposed of will vary with continued operation of Mango II-Milford sites. The amount to be disposed of in any given year, or disposal event may be a determining factor in selection of the method utilized. Mango II-Milford is required by permit to monitor and submit sludge accumulation reports on an annual basis to the DEQ. The monitoring and reporting program will determine accumulation rates and assist in forecasting disposal operations (see section 5). It is anticipated that approximately 20 years of farm operation may be allowed before accumulation will require disposal. However, actual accelerated (or decelerated) accumulation rates may determine that disposal events may occur prior to, or after 20 years of farm operation. 2.0 PROJECTED ANNUAL DISPOSAL QUANTITIES The anticipated annual volume of sludge to be disposed can be estimated using development rates of Mango II-Milford production facilities. Mango II-Milford profiles the sludge layers at every farm every third year. Sludge profiling is completed according to the most recently approved version of the Sampling and Analysis Plan. Mango II-Milford submits an Annual Sludge monitoring report as required by our permits. This report details the measured sludge layer results as well asand the anticipated removal dates. 3.0 ROUTINE SLUDGE REMOVAL The routine removal procedures outlined in this section include land application and sludge drying. 3.1 Land Application Land application of solids is the primary option for sludge utilization. Land application will be done taking into consideration two principal nutrient parameters, nitrogen and phosphorus, as well as taking into consideration the metals content of the solids. Because it is not known what the actual chemical constituency of the solids will be until the material is tested and ready for disposal. Land application will normally be done by the farmer to whom the solids are sold to and should be done at agronomic rates. If the solids are applied to property owned by Mango II-Milford, then the application will be done according to the most recently approved Nutrient Management Plan. 3.2 Sludge Drying Due to liquid hauling costs, it is more economical to dry the solids before applying them at agronomic rates. Below areis the approved procedures and requirements for the Sludge Drying Program at Mango II-Milford: Manure Drying Program Plan Currently, Mango II-Milford has numerous farm sites in operation covered under multiple DEQ permits; each farm site has at least one primary lagoon or digester where manure solids are collected. It is necessary to periodically remove accumulated solids from the bottom of each primary lagoon at the farm sites. Mango II-Milford has implemented a program to remove the solids from the lagoons and dry the manure on a drying pad near the lagoon. The manure is a valuable nutrient source and the drying of the manure will allow the nutrients to be applied to local cropland at agronomic rates without posing a risk to groundwater. This manure drying program is applicable every time a lagoon is de-sludged. Below are the minimum criteria for construction and operation of the sludge drying pad: Depth to groundwater must be at least 20 feet below the bottom of the lagoon liner. Drying pads will not be located in stream beds or washes The drying pad will be located near the primary lagoon at the selected farm site so manure transportation distances will be minimized. Once a site has been selected, a drying pad will be constructed to the below criteria: The existing vegetation will be cleared and grubbed. The existing soil will be scarified to a minimum of 10 to 12 inches below the existing ground surface. The ground surface will be conditioned with 0 to 5 percent above optimum moisture content. The soil will be compacted to a minimum of 90 percent of ASTM D698 on both the outside berms and the floor of the sludge drying pad. Density testing will be performed at a minimum of every 10,000 square feet of surface area. Infiltrometer testing will also be performed prior to any manure transfer. Infiltrometer results must be less than 1.8x10-5 cm/sec. Soil compaction and infiltrometer testing results will be submitted to the DWQ. The sludge pad will not be put into use until the State DWQ has approved its use. Berms will be constructed on the downhill side of the drying area with lateral berms to contain any leachate or run-off from precipitation. Pre- and post- soil sampling is not required by the DWQ, unless a sensitive area is proposed as a drying site. There will be a total of five soil sample locations in the manure drying pad when soil sampling is required. They will be located in each corner of the pad and one in the center. Soils will be sampled (if required) at 1 foot1-foot intervals to a depth of 10 feet below ground surface and then sent for laboratory testing. Soil samples will be collected from the area of greatest impact and analyzed by a certified laboratory for: Phosphorous, Potassium, TKN, Ammonia, Nitrate plus Nitrite as Nitrogen, pH, Calcium, Chloride, Magnesium, Sodium, Sulfate Sumps, or pumping areas, will be strategically placed inside the berm area, and leachate or precipitation will be pumped into a permitted lagoon. While in the liquid stage, manure will not be more than 2 feet in depth. However, in the final stage of drying, stacked manure in windrows may be up to 6-8 feet in height. To sufficiently dry the manure, it may remain on the drying area for up to 9 months. However, it is anticipated that within 30 to 60 days, the decanted and free or excess water will be gone. Once the leachate has been removed, and the manure is dry, it will be formed into wind rows. Wind rows will be periodically turned by a composter until it is ready to be hauled to agricultural fields for application. 4.0 FARM CLOSURE This portion of the plan addresses the event of farm closure at an individual farm, or shutdown of all of Mango II-Milford’s permitted facilities. Ifn the event that a farm is closed, the primary option for sludge management/disposal is in-situ management. By allowing in-situ management of sludge material within the lined lagoons and/or digesters, without destroying and abandoning the lagoon berms and liners, it will allow for future use of the lagoons and/or digesters to meet the evolving business needs of future owners or tenants over time. 4.1 In-Situ Management The operation for in-situ stabilization at farm closure would be the removal of liquid from the system. This could be done by transferring the liquid to the evaporation ponds or by natural evaporation. Land application of lagoon liquids and/or solids shall be done according to the most recently approved version of the Nutrient Management Plan and the Manure Drying Plan. Naturally high evaporation rates in the area will be utilized to dry out the liquid from the lagoons, and facilitate final drying of the solids. Historic sludge samples taken over the years verify that sludge contains approximately 10-15% solids. Thus, once the sludge is dried, the dried sludge volume should only be 10-15 % of the total amount originally measured. For example, a 10-foot sludge layer would evaporate down to 1-1.5 feet of dried sludge. 4.1.1 Requirements for In-Situ Management of Sludge and Permit Closure For in-situ management of sludge to be considered, the following conditions should be met: The farm site should be depopulated, and any remaining pumpable liquid in the primary lagoon or digester (above the sludge layer) should be removed and/or evaporated. Site groundwater monitoring wells must be in -compliance after depopulation. Monitoring wells will continue to be monitored according to the permit requirements until the pumpable liquid has been removed and/or evaporated. Once the pumpable liquid has been removed and/or evaporated, the site’s monitoring wells will be monitored annually for a period of two years. If the site’s monitoring wells are out of compliance at the time of depopulation, or if they exceed the site-specific Protection Levels outlined in the permit, during the post depopulation monitoring period, they must continue to be monitored according to the permit requirements until the monitoring wells have been in compliance for a minimum of two years. If the above conditions are met, then the individual farm site can be removed from the permit at the option of Mango II-Milford. After the farm site has been removed from the permit,. Mango II will: Cap the monitor wells in such a way as to prevent any contamination from entering the wells, and Secure and lock each monitoring well monument. After permit closure, if a new owner, tenant, or the current owner desires to use the lagoons or digesters again, a new application for a groundwater discharge permit and liner integrity assessment (for both primary and secondary lagoons) will have to be submitted and approved by the DWQ before the lagoons or digesters could be put back into use. 4.1.2 Justification for long- term in-situ management of sludge and permit closure Below are the justifications explaining how the in-situ management of dried sludge in a lagoon is protective of groundwater: Once the farm is depopulated, and the pumpable liquids are removed from the sludge layer, and no new liquids are introduced by the farm, there willould likely be insufficient hydraulic head to facilitate transport of contaminants into the groundwater. Once the sludge layer is dried, no water will be present to allow for the transport of contaminants to groundwater. According to the USGS, inwith cooperation with the Utah Department of Natural Rresources Division of Wwater Rrights, in a report titled ”Water Resources of the Milford Area, Utah, with emphasis on ground water” Technical publication number 43,. uUnder the heading “Infiltration from precipitation on the valley floor” it says, “The average annual precipitation on most of the valley floor is less than 10 inches (254mm) (pl.1), far less than could be consumed by evapotranspiration under normal conditions. Contributions to recharge from precipitation probably are so small everywhere on the valley floor, except on irrigated fields, that it may be considered nil.” Page 21 With negligible recharge to the aquifer from precipitation, it is unlikely that contaminants are unlikely tocould reach the aquifer once the water is removed from the lagoons. Milford valleyValley pan evaporation is 78 inches per year. The first unconfined aquifer ranges from around 30-200 feet below the bottom of the lagoons. The drinking water aquifers are 500-800 feet below the bottom of the lagoons, with some confining layers in between. Per the DWQ- issued construction permits, underlying the synthetic liner is a compacted 8-inch layer of soil that was compacted to 90% dry density. The above reasons demonstrate that the in-situ management of sludge in dormant lagoons will not present an ongoing risk to human health or the environment, groundwater quality, or future beneficial uses of groundwater.  4.2 Other Waste Handling Facilities Abandonment Farm closure will require abandonment of other regulated on-farm waste retention and conveyance facilities. The concrete pits under the slatted or grated flooring of the production building will be emptied of waste. The pits will be filled once with fresh water and then once again drained. The pipeline into the lagoon systems will be permanently capped so that no further inflow will be introduced into the abandoned lagoon area. 4.7 Notification of Closure and Abandonment In the event a farm or treatment system is to be closed, an application requesting removal from the permits will be submitted to the DEQ. Detailed information shall be presented in the request and approval shall be received prior to closure. 5.0 SLUDGE MONITORING Mango II-Milford will commence a detailed sludge monitoring program. The purpose of the monitoring program will be to monitor accumulation rates, calculate the remaining sludge storage capacity remaining, and project future sludge disposal events. In addition, sludge samples will be taken and analyzed for chemical composition. The monitoring will result in an annual report, which shall be submitted to the DEQ by February 1, of each year. 5.1 Sludge Monitoring Schedule and& Methodology Sludge accumulation monitoring will occur at each currently populated farm at least once every 3 years. Sludge monitoring is not required once a farm has been depopulated. Preferred monitoring will occur in the fall of the year. At Mango II-Milford’s option, spring monitoring may be done. This will provide data on undigested materials in the lagoon due to the seasonal cooling and digestive inactivity in the treatment ponds. If spring monitoring is done, the data from this monitoring will be included in the annual report. Fall monitoring will provide a comparison of accumulation rates after seasonally high digestion activity during the summer months. The method used to monitor sludge accumulation shall be detailed in the most recently approved Sampling and Analysis Plan. Sludge Sampling and Testing Sludge sampling shall be done at the representative farm sites as outlined in the Groundwater Discharge Permits issued by the DWQ. Sampling will be done according to the most recently approved Sampling and Analysis Plan. Reporting Results from sludge monitoring shall be combined and reported on a spreadsheet indicating all data obtained. The report shall include columnar data for each of the following: farm site, initial site population date, site depopulation date, the date of last sludge removal, overall liquid depth, sludge depth measurements, average depth, volume of accumulated solids, design storage volume, percentage of design volume taken, and projected sludge capacity/disposal date. The projected sludge capacity/disposal date shall be preliminarily calculated in linear accumulation rates.