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HomeMy WebLinkAboutCapacity Report 2022-07-25 GreatWest E N G 1 N E E R I N G July 25, 2022 Jim Simon, District Manager • Gallatin Solid Waste Management District P.O. Box 461 Three Forks, MT 59752 RE: Gallatin Waste Management District Landfill Task Order No. 6 Annual Compaction, Capacity and Performance Evaluation Dear Jim: Per Task Order No. 6 of the 2022 On-Call Engineering Services Contract, we conducted a GPS topographic survey on June 29, 2022, to estimate the remaining life of the landfill and evaluate the landfill performance. The following data was used to perform this work: 1) Field surveys conducted every six months to a year, 2) As-built surveys of completed Phase 3 cell, 3) As-built surveys of completed Phase 4 cell, HELENA 4) As-built surveys of construction projects at the landfill, •• :. 2501 Belt View Drive 5) Soil usage data provided by the District, Helena, MT •. 6) Waste quantity data provided by District, and • 7) Master Plan for landfill. 0. 449-8631 BILLINGS Class II Waste Area Performance Evaluation (Phases 2, 3, and 4) 6780 Trade Center Avenue Topographic information from the field survey was used to generate a computer model and a Billings, MT •101 contour map of the landfill area on June 29, 2022. Great West Engineering compared the new 0. 000 • model to previous topographic surveys to evaluate the landfill performance over the period. Table 1 shows the Phase 2 landfill performance calculated with GPS surveys over each period BOISE the Phase 2 cell was open and the total since we have been involved in the landfill operation. Portions of the Phase 2 cell were closed in 2013 and has not received any waste since Lane Suite 201 December 2011. Great West Engineering has not surveyed the Phase 2 cell since December Boise, ID 83703 2011. The Phase 2 Closure area was surveyed for the purposes of record drawings that were 576-6646 submitted to the Montana DEQ. GREAT FALLS Great Falls,MT .,0 0. 0• SPOKANE Spokane,9221 N Division Street Suite F 99218 0. 0 www.greatwesteng.com Y:1Shared\Helena Projectsl1-05119-LOGANIPROJECTIcorrespondence\Capacity Report 2022-07-13.docx GreatWest Table 1 Gallatin County Landfill Municipal Solid Waste Phase 2 Cell Performance Analysis Summary 05118105- 10116105- 03131106- 11109106- 10130107- 8122108- 4117109- 11126109- 612912010- 411212011- Phase 2 10/15/05 03/30/06 11/08/06 10/29/07 8/21/08 4/16/09 11/25/09 6/28/2010 4/11/2011 1218/2011 Total Total Fill 123,015 218,970 68,969 61,328 81,190 66,261 842,147 Volume 41,836 CY 56,005 CY CY CY 57,555 CY CY 67,018 CY CY CY CY CY 9,844 17,789 10,526 15,014 9,738 134,777 Soil Volume 0 0 18,732 CY 38,500 CY CY CY 14,634 CY CY CY CY CY Waste to Soil Ratio NA NA 5.6:1 4.7:1 4.85:1 2.88:1 3.58:1 4.83:1 4.41:1 5.80:1 5.25:1 Tonnage 28,720 43,646 77,587 116,490 31,498 36,893 41,560 532,319 Accepted Tons Tons Tons Tons Tons Tons Tons 42,254 Tons 60,187 Tons 53,484 Tons Tons Compacted Waste 1,373 1,559 1,488 1,291 1,320 1,442 1,587 1,663 1,819 1,892 1,505 Density LB/CY LB/CY LB/CY LB/CY LB/CY LB/CY LB/CY LB/CY LB/CY LB/CY LB/CY Volume Per 1.46 1.28 1.59 1.88 1.83 1.87 1.61 1.45 1.35 1.24 1.58 Ton Ratio I CY/Ton CY/Ton I CY/Ton I CY/Ton I CY/Ton CY/Ton I CY/Ton CY/Ton CY/Ton I CY/Ton I CY/Ton Page 2 of 10 GreatWest Gallatin County Landfill Municipal Solid Waste Phase 3 Cell 17 Performance Analysis Summary Phase 3 4117109- 11126109- 121912011- 1011112012- 312112014- 31612015- 411112016- 312512017- 411212018- 611412019- 612612020- 71812021- Total to 11125/09 12/812011 10/1012012 3/2012014 3/512015 4110/2016 3/2412017 4/1112018 6113/2019 6/2512020 7/712021 6/2912022 Date Total Fill 24,465 118,087 181,494 131,209 158,173 138,082 169,187 192,661 210,766 267,452 92,825 1,828,153 Volume CY 0 CY CY CY CY CY CY CY CY CY CY CY 3,708 23,759 27,506 21,786 33,760 365,319 Soil Volume CY 0 CY CY CY CY 31,940 CY 33,588 CY 28,764 CY 49,398 CY 58,140 CY 19,836 CY CY(2) Waste to Soil Ratio 5.6:1 NA 3.97:1 5.60:1 5.02:1 3.69:1 3.32:1 4.04:1 5.69:1 3.27:1 3.60:1 3.68:1 4.00:1(2) Tonnage 13,458 65,028 115,075 91,371 103,490 97,766 113,160 139,465 120,901 169,514 65,873 1,173,874 Accepted Tons 0 Tons Tons Tons Tons Tons Tons Tons Tons Tons Tons Tons Compacted Waste 1,297 1,379 1,495 1,670 1,664 1,842 1,669 1,701 1,498 1,620 1,805 1,605 Density LB/CY NA LB/CY LB/CY LB/CY LB/CY LB/CY LB/CY LB/CY LB/CY LB/CY LB/CY LB/CY Volume Per 1.82 1.82 1.58 1.44 1.53 1.41 1.50 1.38 1.74 1.58 1.41 1.56 Ton Ratio CY/Ton NA CY/Ton I CY/Ton CY/Ton I CY/Ton I CY/Ton I CY/Ton I CY/Ton I CY/Ton I CY/Ton I CY/Ton I CY/Ton (1) Performance analysis data prior to 2009 has been omitted from Table 2. This data can be found in previous Annual Compaction Reports. (2) Individual soil volume quantities do not add up to the total quantity to date. This is because "recycled soil" is counted during the individual time periods but not in the overall total. 8,352 CY of"recycled soil" has been reported to date. Page 3 of 10 GreatWest E N G I N E E R I N G The Phase 3 and Class IV fill areas have overlapped. With consultation from the District, the Class II and Class IV waste volumes will be combined. All waste placed in Phase 3 and Class IV area will be tracked in the Phase 3 Cell and reported in Table 2. The District began tracking recycled soil in 2019. Recycled soil is generally counted in individual periods but not in the overall total. Removing the recycled soil from the soil usage increases the waste to soil ratio to 4.00:1 in the Phase 3 cell. Recycling soil ultimately increases the life of the site by utilizing less airspace with soil. The District should continue to try to recycle as much soil as possible. Recycled soil was not used in Phase 3 during this time period. Table 2 shows the Phase 3 landfill performance and the overall average of that cell. The Phase 3 cell did not receive any waste for three time periods due primarily to finishing filling the Phase 2 cell. Performance analysis data prior to 2009 has been omitted from Table 2. This data can be found in previous Annual Compaction Reports, or can be provided upon request. Table 4 shows the overall landfill performance for Phases 2, 3, and 4 and the overall landfill performance for Phases 2, 3, and 4 combined. As measured by the volume per ton ratio, the overall space utilization for the Phase 3 cell over the last period was 1.41 CY/Ton. This was 10.8% less air space utilization than last time period. The overall performance of the landfill is measured by the volume per ton ratio. The two components which directly impact the overall landfill performance are the compacted waste density and the waste-to-soil ratio. Phase 4 achieved a compacted waste density of 1,805 pounds per cubic yard over the last period. The staff should be commended for the continued excellent compaction. The industry standard for compacted waste density at landfills that operate 826-equivalent compactors is 1,200 Ib/cy. The District staff is exceeding that metric with the operation. This high compaction is due to the dedicated and consistent application of compaction techniques with quality equipment and operators. The District needs to continue with the compaction techniques it currently uses on the site. The overall waste-to-soil ratio for the period was 3.68:1. This is a 2% decrease in soil usage over the previous period. The District needs to continue to utilize the approved alternative daily cover as often as possible in place of soil. In summary, the industry standard for landfills this size is a compacted waste density of 1,200 Ib/cy and a 3:1 waste-to-soil ratio, resulting in an overall volume per ton performance of 2.22 CY/Ton. The overall performance measured by GPS over this last period was 36.5% better than standard landfill performance metrics. The landfill staff should be commended for obtaining this outstanding waste density and overall landfill performance, ensuring the landfill life is maintained and, in this case, actually extended via excellent performance criteria. This is See what's possible. Page 4 of 10 ImIlo /G^reatW�est E N G I N E E R I N G especially true in this instance because the landfill has begun to commingle Class II and Class IV waste streams. Class IV materials are more difficult to obtain high compaction levels because of the nature of the waste. Table 3 Gallatin County Landfill Municipal Solid Waste Phase 4 Cell Performance Analysis Summary 6/14/2019-6/25/2020 6/26/2020-7/7/2021 7/8/2021-6/29/2022 Phase 4 Total to Date Total Fill Volume 102,186 CY 25,624 CY 210,275 CY 338,085 CY Soil Volume 21,800 CY 4,662 CY 39,348 CY 65,108 CYO) Waste to Soil Ratio 3.69:1 4.50:1 4.34:1 4.19:10 Tonnage Accepted 47,847 Tons 9,844 Tons 112,371 Tons 170,062 Tons Compacted Waste Density 1,190 LB/CY 939 LB/CY 1,315 LB/CY 1,246 LB/CY Volume Per Ton Ratio 2.14 CY/Ton 2.60 CY/Ton 1.87 CY/Ton 1.99 CY/Ton (2) Individual soil volume quantities do not add up to the total quantity to date. This is because "recycled soil" is counted during the individual time periods but not in the overall total. 702 CY of"recycled soil' has been reported to date. Phase 4 began accepting waste in the Spring of 2019. Table 3 shows the Phase 4 landfill performance to date. As measured by the volume per ton ratio, the overall space utilization for the Phase 4 cell over the last period was 1.87 CY/Ton. This is 28.1% less airspace utilized than last time period, and 15.8% less airspace utilized than the industry standard. The large airspace utilization swing can mostly be attributed to previous periods using large amount of gravel and soil used to construct access roads in the Phase 4 cell, not compacting the waste as much to prevent waste from puncturing the liner, and placing soil cover over a thin layer of waste and not achieving a full lift thickness. The Phase 4 area achieved a compacted waste density of 1,315 pounds per cubic yard over the last time period. The industry standard for compacted waste density at landfills which operate 826-equivalent compactors is 1,200 Ib/cy. Landfill staff exceeded this metric in the last year by 9.6%. The waste-to-soil ratio for this time period is 4.34:1. This is 44.7% less soil usage than industry and less soil usage than is typical for the landfill. The District needs to use the approved alternative daily cover as often as possible instead of soil. While ADC was not practical for the first lift in Phase 4, ADC should be used in the future. See what's possible. Page 5 of 10 /G^reatW�est E N G I N E E R I N G Overall, the landfill is performing exceptionally well, and landfill staff should be commended. If landfill staff places waste in Phase 4 as they have done historically throughout other phases of the landfill, performance metrics will return close to where they have been historically. Table 4 Gallatin County Landfill Municipal Solid Waste Phase 2,3,and 4 Cells Performance Analysis Summary Phase 2 Total Phase 3 Total to Date Phase 4 Total to Date Phases 2,3 and 4 Total to Date Total Fill Volume 842,147 CY 1,828,153 CY 338,085 CY 3,008,385 CY Soil Volume 134,777 CY 365,319 CY 65,108 CY 565,204 CY Waste to Soil Ratio 5.25:1 4.00:1 4.19:1 4.32:1 Tonnage Accepted 532,319 Tons 1,173,874 Tons 170,062 Tons 1,876,255 Tons Compacted Waste 1,505 LB/CY 1,605 LB/CY 1,249 LB/CY 1,536 LB/CY Density Volume Per Ton Ratio 1.58 CY/Ton 1.56 CY/Ton 1.99 CY/Ton 1.60 CY/Ton Class IV Area Performance Evaluation Great West has also measured Class IV performance since the Class IV area opened. Class IV materials are much more difficult to obtain high compaction levels because of the nature of the waste. Industry standard metrics for Class IV landfills are 750 Ib/cy compacted waste density and a waste-to-soil ratio of 6:1. This results in an overall volume per ton ratio of 3.1 CY/Ton. Table 5 shows that the landfill has historically exceeded industry metrics with the Class IV operation. Considering the landfill has begun commingling Class II and Class IV waste streams, the Class IV area performance is being accounted for with Phase 3 performance. See what's possible. Page 6 of 10 0000* GreatWest E N G I N E E R I N G Countyle 5 • Gallatin Class IV Performance Analysis 411712009- 1112612009- 71812010- 411512011- 121912011- 1011112012- 312112014- 31612015- 411112016- 312512017- 411212018- 11125/2009 7/712010 4114/2011 1218/2011 10/10/2012 3/20/2014 3/512015 4/1012016 3/2412017 4111/2018 6113/2019 Total Total Fill Volume 33,767 CY 20,768 CY 46,752 CY 51,699 CY 28,538 CY 69,737 CY 58,665 CY 65,472 CY 61,868 CY 74,763 CY 111,849 CY 523,878 CY Soil Volume 3,780 CY 2,285 CY 6,432 CY 6,977 CY 6,225 CY 13,739 CY 8,465 CY 13,940 CY 13,960 CY 15,624 CY 21,834 CY 113,261 CY Waste to Soil Ratio 7.93:1 8.09:1 6.27:1 6.40:1 3.58:1 4.08:1 5.93:1 3.70:1 3.43:1 3.79:1 4.12:1 4.51:1 Tonnage 29,381 27,577 27,197 26,721 277,000 Accepted 1 14,557 Tons 9,175 Tons Tons Tons 14,622 Tons 25,957 Tons 21,787 Tons Tons Tons 33,105 Tons 46,921 Tons Tons Compacted Waste 1,457 1,233 1,056 1,116 1,084 Density 970 LB/CY 993 LB/CY LB/CY LB/CY 1,310 LB/CY 927 LB/CY 868 LB/CY LB/CY LB/CY 1,120 LB/CY 1,042 LB/CY LB/CY Volume Per 2.32 1.59 1.87 2.41 2.32 Ton Ratio I CY/Ton 1 2.26 CY/Ton I CY/Ton I CY/Ton 1 1.95 CY/Ton 2.69 CY/Ton 2.69 CY/Ton CY/Ton CY/Ton 2.26 CY/Ton 2.38 CY/Ton 2.25 CY/Ton Page 7 of 10 GreatWest E N G I N E E R I N G Life Estimates The performance data, tonnage and the Landfill Master Plan were used to estimate the remaining life of Phase 3, the Class IV area, Phase 4, and the overall landfill. To estimate the remaining life of Phase 3, the first step is to calculate the remaining air space in the cell. The computer-generated land surface model from the June 29, 2022 survey was compared to the interim fill plan for Phase 3 to determine the remaining air space. The interim fill slopes for Phase 3 in the master plan were designed at a 5:1 grade. The slopes, thus far, have been built at a 4:1 grade. To accommodate this change, Great West Engineering, with consultation from the District, changed the interim fill slope design to a 4:1 grade. This does not impact the overall life of the facility but changes the life expectancy of the Phase 3 cell. This meets the requirements of the seismic design demonstration. In order to estimate the remaining life of Phase 3, we needed to project the waste generation throughout the remaining life of this cell. Currently 180,000 tons/year is the best estimate of the annual tonnage for projections on remaining site life. This has increased from 160,000 tons/year from the previous estimates. The total air space includes the final cover for the portion of Phase 3 fill which reaches the final proposed elevations, so this is subtracted out of the air space available for waste and daily/intermediate soil cover. The overall performance of Phases 2 and 3 is the best estimate of how much daily and intermediate cover will be utilized at the site. However, the District must continue to use alternative daily cover(ADC)to the extent possible to minimize the landfill's air space usage. We estimate that the landfill will be able to utilize soil long term at a 4:1 waste to soil ratio. The landfill nearly achieved this goal this period. To date, the landfill is slightly above this ratio and needs to continue reducing the soil usage to achieve a 4:1 waste to soil ratio consistently. The estimated daily and intermediate soil cover usage is then subtracted from the available air space to determine the volume available for waste. The last variable to determine is the compacted waste density. The landfill averages 1,536 Ib/cy historically. The industry standard for compacted waste density for a landfill of this size with an 826 equivalent compactor is 1,200 Ib/cy. It appears from the last 19 periods that the District should be able to consistently achieve waste densities of 1,280 Ib/cy and above. The landfill staff does an excellent job of placing the waste in thin lifts and compacting the waste with multiple equipment passes in both directions. For the basis of these life estimates, we used a 1,280 Ib/cy waste density. The life estimate analysis is summarized in Table 6. The estimates assume there will be no large "one-time" disposal projects. An example would be a large hailstorm or earthquake generating a great deal of construction and demolition wastes. The capacity estimate also assumes that the District will not expand its service area during the remaining landfill life. If the District does expand its service area in the future, the life estimate would need to be updated. The ultimate life of the site will be highly dependent on the waste tonnage received Page 8 of 10 See what's possible. GreatWest E N G I N E E R I N G at the site and the landfill performance. If the tonnage increases over this estimate or the landfill performance drops, the District will have less life than predicted. In September 2010, an Addendum to the Landfill Master Plan was designed to include the Class IV Expansion. During this Master Plan update, a new life estimate was developed. Table 6 uses the updated Master Plan numbers to determine life projection estimates. The volumes used to create Table 6 were calculated using CAD applications. The Class IV area has been built with slightly steeper slopes (-3.5:1)than 4:1 which increased height and the capacity of the Class IV area. To accommodate this change, Great West Engineering, with consultation with the District, redesigned the remainder of the final fill slope of the Class IV area to a 4:1 slope from the current elevation. The redesign of the final fill for the Class IV was combined with the final fill for the Phase 3 cell to determine the life expectancy. The redesign was completed July 23, 2019. Based on the waste streams received prior to combining Class IV waste and Class II waste volumes, the landfill accepts approximately 20% Class IV waste and 80% Class II waste on average. An effective combined density will be used to estimate the remaining life. Therefore, the life was estimated using 80% of 180,000 tons/year(144,000 tons/year)for Class II waste and 20% of 180,000 tons/year(36,000 tons/year)for the Class IV waste estimates. The life of each area was calculated and is shown in Table 6. The life estimates for the waste accepted in Phases 3 and 4 shown in Table 6 are based on an effective volume per ton ratio of Class 11 and Class IV wastes. The Class II wastes are estimated at a 1,350 Ib/CY compacted waste density, 4:1 waste-to-soil ratio and an overall volume per ton ratio of 1.85 CY/Ton. The Class IV waste are estimated with a 1,000 Ib/CY compacted waste density, 5.5:1 waste-to-soil ratio and an overall volume per ton ratio of 2.36 CY/Ton. An effective volume per ton ratio of Class II and Class IV wastes based on 80% Class II and 20% Class IV equals 1.95 CY/Ton. The Phase 3 and Phase 4 cells will accept both Class 11 and Class IV waste streams at 180,000 tons/year. The Phase 3 cell will reach capacity in 0.17 years and the Phase 4 cell will reach capacity in 3.43 years. Therefore, the total life of the landfill is 3.6 years (Phase 3 —0.17 years + Phase 4—3.43 years). Gallatin County Landfill Life Projection Estimates(July Table 6 Phase 3 and Class IV Life(Based on 180,000 Tons/Year) 0.17 years Phase 4 Life(Based on 180,000 Tons/Year) 3.43 years Total Life(Based on 180,000 Tons/Year) 3.6 years Page 9 of 10 See what's possible. /G^reatWest E N G I N E E R I N G Thank you for the opportunity to assist the District in the operation and planning of the landfill. If we can be of any further assistance or you have any questions or comments, please contact me at my office. Sincerely, Great West Engineering, Inc. Stephanie Beckert, PE Project Manager Page 10 of 10 See what's possible.