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6.4. SR 02-20-2007 Item Description Request by Tiller Corporation for Conditional Use Permit to Amend Existing Hours of Operation, Case No. CU 07-08, Public Hearin Item Number 6.4. Prepared by Rebecca Haug, Environmental Administrator Reviewed by City of Elk River REQUEST FOR COUNCIL ACTION Agenda Section Meeting Date Community Development February 20, 2007 Introduction Tiller Corporation is proposing to amend their Conditional Use Permit to extend their current hours of operation. The volume of material being mined, processed, and sold is expected to be consistent with recent past years. Discussion Tiller is proposing the hour extension to increase efficiency and equipment use. As stated in the memo dated December 26, 2006 from Michael Caron, Tiller Corporation, they operate two facilities. One facility is in the City of Elk River and the other is in Livonia Township. Each facility operates 45 to 50 hours per week (one shift) during the mining season. Their proposal would allow them to work at one site for half the season with two shifts and then move the equipment and crews to the other site for the second half of the season. The Elk River shift would begin in mid March (weather permitting) and end in mid July. Operating hours are proposed to be 4:00 a.m. to 10:00 p.m. Monday through Friday. Operating hours may need to be adjusted if sales increase or decrease. Currently, their CUP allows them to operate from 7:00 a.m. to 7:00 p.m. Monday through Saturday. On occasion, their hours have been extended with approval from the Environmental Administrator. Equipment needing back up alarms will be fitted with visual alarms for night time operations along with a broad based frequency alarm system that the applicant will discuss during their brief presentation. The applicant also conducted a noise assessment which is attached. At the Planning Commission meeting on February 13,2007, a condition was added to require the applicant to conduct another noise assessment after 60 days of operation under the proposed new hours. The proposed changes will not affect trucking or hauling operations. They will remain with the code requirement of 7:00 a.m. to 7:00 p.m. Monday through Saturday. On occasion, their hours may be extended with approval from the Environmental Administrator. A public meeting was held on Tuesday, February 6, 2007 to answer questions the public had in regards to the proposed change. There were no residents in attendance at this meeting. This is not an unusual request for a gravel operation. Aggregate Industries has extended hours for their operation. S:\Council\REQUEST COUNCIL ACTION-feb20.doc This proposal was presented to the Sherburne County Planning Commission on January 18, 2007 and was recommended for approval. At the February 6, 2007 Sherburne County Board of Commission meeting, the project was approved. The City of Elk River Planning Commission recommended approval on February 13,2007. Financial Impact N/A Attachments . Memo dated December 26, 2006 from Michael Caron, Tiller Corp . Location Map . Noise Assessment and letter summarizing the Noise Assessment from Michael Caron, Tiller Corp Action Requested Staff is recommending approval of the applicant's request to extend their hours of operation with an additional condition requiring them to conduct another noise assessment after 60 days of operation. Council Action Motion by _ Second by _ Vote Follow Up S:\Council\REQUEST COUNCIL ACTION-feb20.doc 'Ji'ILLER CORPORATION Tiller Corporation and its opemting divisions Corporate Office: PO Box: 1480 7200 Hemlock Lane, Suite 200 Maple Grove, Minnesota 55311 Barton Sand & Gravel Co. Commercial Asphalt Co. Barton Enterprises, Inc. general: (763) 425-4191 facsimile: (763) 425-7153 web: www.tillercorp.com December 26, 2006 Rebecca Haug Environmental Administrator 13065 Orono Parkway Elk River, MN 55330 Re: Amendment,to Existing CUP Dear Ms. Haug: Enclosed are application forms for amending an existing copditional use permit for mining to allow for an extension of operating hours. The volume of material being mined, processed and sold at the Elk River facility is expected be consistent with recent past years. The only change being requested is in the operating hours for mining and processing activities. Tiller Corporation and its operating division Barton Sand & Gravel Co. operate facilities in the city of Elk River and Livonia Township. Currently, the Elk River site produces mainly washed concrete aggregates while the Livonia site produces mostly bituminous aggregates. Each facility has similar crushing and processing equipment and each site operates 45 to 50 hours per week (one shift) during the entire minin,g season. We are proposing operational changes at these facilities to increase efficiency and equipment use. Instead of mining and processing with one shift at both locations for the entire season, we intend mine and process for first half of the season at one facility utilizing two shifts and then move the equipment an.d crews to the other facility for the second half of the season. Anticipated scheduling has us starting in Elk River around mid March (weather permitting) and completing the year's production around mid July. We would then move to Livonia and operate until the end of the season in mid to late November. Operating hours would be approximately 4:00 a.m. to 10:00 p.m. (two shifts) Monday through Friday. These This Company is an Equal Opportunity Employer December 26, 2006 Page 2 of2 hours are based on our production goals and anticipated sales. Operating hours may need to be adjusted if sales increase or decrease. Equipment needing backup alarms will be fitted with visual alarms for night time. operations. Audio alarms will be used only during day light hours. Minnesota Pollution Control Agency Rules Chapter 7030 regulating noise will be followed. The proposed operational changes will not impact trucking or hauling operations. All trucking will occur between the hours of 7:00 a:m. and 7:00 p.m. Monday through Saturday. As in the past, any exceptions to these hours will need City approval. Please contact me if you have questions or need additional information. I may be reached at (763) 315-6004. Respectfully, Michael Caron Director of Land.U se Affairs enc: // ~----------/ ~ ----------- v ~,w ow~n'n;r~0L'" ~0~~} ;b ~~~~ 5r ;:.... ~.----~ \' ~ -- A'< '" K~^ 0 ~c-=::..-~~>~- >_~ / )'~ '"000 )I ~"P ,,,,0 ~ ~~b: ( / r-- ~ Vl m 2 0 :-=\l ~ ~ I I'~ :Or~f L-, ~ --~~lrTr z \\ <( --0 =4 \\ I ~7~~ o \ ~ -!---------- ~ 8 ~ <( \ 0 ,,'-..) 71--- ?2 \ ~~ ~ 0 ~ I: ~ \ \ ====( ~ I", \ ^~ ~ \ \ ~ ~ 0/-' ~~h J:<,~G \\ l~~:~,XJI \ \ ~-"'-' flj' r;J c \ \ iV"/(j041~tv:]~ ~ U \~ \ ~41tv ~J:] S Of/O lJotv e~'--l \ ~'i;\'" \ LL 'ON O\fO~ "lNnOO ' f'--.- ~ ~ L ~ (~~ ~{ ~y ~1)~\ ~ ~ ~ \2 ~ =~ ~ ~:i'~ / ~ : IJ / lo"~~c>- ~ ~~ 0 ~ ;y, UfL ~~o, " S ,( '" Q(;% "''2 r ~ '0 r"\ I- L:L::S k{<O, t;:~, ~ NO:di ~~ Z -'-1 ~ '2 A,~ \:-< m "-' ;~ tl~ '" ~~- ~~ /\ljcr !~ '15)\B" ~ ~~ ~~ " z W ::0 Z > <( lOOBd I r- en o N \ '" ::: ~ ~ '" ~ :<; 0:: ~ 2 ~ Q o u '" ~"" o o Q o ~ ~ if. Q ,,~= ~ ~ ~q, "'0 ~ ~~ ~~~ I ~~~ ~ ~ (i~ ~ ~. \Cy ~ ------ 000 ------ '-( ~ ~ ~~G -~ --~ r----, -....J A 1--1 ~ Tiller Corporation Sand and Gravel Operations City of Elk River, MN and Livonia Township, MN Noise Assessment Prepared for the Tiller Corporation by David Braslau Associates, Inc. 1313 5th St. SE Suite 322 Minneapolis, MN 55414 Tel: 612-331-4571 Fax: 612-331-4572 Eml: david@braslau.com 22 January 2007 Tiller Corporation Elk River and Livonia Quarries Noise Assessment Table of Contents 1. 0 INTRODUCTION ............................ .................................................................... ............. 1 1.1. Objectives of this Report ................. ........ ............. ................ ......... ...... .......... ........... ....... 1 1.2. Minnesota Noise Standards ............................................................................................. 1 1.3. Organization of this Report ............................................................................................. 1 2.0 ASSUMPTIONS ON MINING ACTIVITy.................................................................... 2 2.1. Livonia Mining Operation .................... ..................................... ............. ........... .............. 2 2.1.1. 2006 Operations....................................................................................................... 2 2.1.2. 2007 and Future Operations .................................................................................... 2 2.2. Elk River Mining Operation............................................................................................2 2.2.1. 2006 Operations.......................................................................................................2 2.2.2. 2007 and Future Operations .................................................................................... 6 2.3. Elk River Wash Plant Facility .........................................................................................6 2.3.1. 2006 Operations....................................................................................................... 6 2.3.2. 2007 and Future Operations .................................................................................... 6 3.0 NOISE MONITORING PROGRAM ............................................................................ 10 3.1. Noise monitoring locations and results ......................................................................... 10 3.2. Comparison of Monitored and Modeled Levels............................................................ 11 4.0 PREDICTION 2007 AND FUTURE NOISE LEVELS................................................ 13 4.1. Modeling methodology and assumptions...................................................................... 13 4.2. Livonia Mining Operation............................................................................................. 13 4.3. Elk River Mining Operation.......................................................................................... 15 4.4. Elk River Wash Plant Facility ....................................................................................... 17 5.0 SUMMARY OF FINDINGS AND RECOMMENDATIONS...................................... 19 5.1. Sound Levels Associated with 2006 Operations ........................................................... 19 5.1.1. Livonia Mining Operation..................................................................................... 19 5.1.2. Elk River Mining Operation.................................................................................. 19 5.1.3. Elk River Wash Plant Facility ............................................................................... 19 5.2. Estimated Sound Levels Associated with 2007 Operations .......................................... 19 5.2.1. Livonia Mining Operation..................................................................................... 19 5.2.2. Elk River Mining Operation.................................................................................. 19 5.2.3. Elk River Wash Plant Facility ...............................................................................20 5.3. Estimated Sound Levels Associated with Future Operations........................................ 20 5.3.1. Livonia Mining Operation..................................................................................... 20 5.3 .2. Elk River Mining Operation.................................................................................. 20 5.3.3. Elk River Wash Plant Facility ............................................................................... 20 5.4. Concluding Comment.................................................................................................... 20 David Braslau Associates, Inc. Tiller Corporation Elk River and Livonia Quarries Noise Assessment Figure 2.1 Figure 2.2 Figure 2.3 Figure 2.4 Figure 2.5 Figure 2.6 Figure 4.1 Figure 4.2 Figure 4.3 List of Figures Livonia Mining Operation - General Location 2006......................................... 3 Livonia Mining Operation - 2007 and Future Layout....................................... 4 Elk River Mining Operation - General Location 2006...................................... 5 Elk River Mining Operation - 2007 and Future Layout ................................... 7 Elk River Wash Plant Facility - General Location 2006................................... 8 Elk River Wash Plant Facility 2007 and Future Layout .................................. 9 Livonia Mining Operation - 2007 and Future Assumptions ........................... 14 Elk River Mining Operation - 2007 and Future Assumptions ....................... 16 Elk River Wash Plant Facility - 2007 and Future Assumptions..................... 18 David Braslau Associates, Inc. Tiller Corporation Elk River and Livonia Quarries Noise Assessment Table 1.1 Table 3.1 Table 3.2 Table 3.3 Table 4.1 Table 4.2 Table 4.3 List of Tables Minnesota Noise Standards for Residential Land Uses ..................................... 1 Monitored (L50) Sound Levels (dBA) at Non-Mining Sites ............................ 10 Assumed Sound Level Spectra for Mine Sources (dB at 100 feet) .................. 11 Predicted Crusher Complex Sound Levels (dBA) ............................................ 11 Livonia Mining Operation Sound Levels (L50 in dBA) ................................... 13 Elk River Mining Operation Sound Levels (L50 in dBA)................................ 15 Elk River Wash Plant Sound Levels (L50 in dBA)........................................... 17 David Braslau Associates, Inc. Tiller Corporation Elk River and Livonia Ouarries Noise Assessment 1.0 INTRODUCTION 1.1. Objectives of this Report This report evaluates existing and future sound levels associated with the mining and processing of sand and gravel at two locations in Sherburne County, Minnesota. One mine ("Livonia Mining Operation" is located in Livonia Township approximately six miles north of Elk River, Minnesota, on the west side of TH 169. The other mine, which is approximately three miles south of the Livonia Mining Operation has two active mining areas. The "Elk River Mining Operation" is located immediately west ofTH 169 and south ofthe new County Road 33. The "Elk River Washplant Facility" is located west of the Elk River Mining Operation and just east of the Sherburne County recreational trail. This report has two primary objectives: (1) To determine if the existing operations can continue into the nighttime hours as defined in the Minnesota noise standards (10 pm to 7 am) without exceeding the nighttime noise standards at the nearest homes. The L50, or level exceeded 50% of the time (median sound level) is the appropriate metric against which to compare the highest noise levels, which are associated with crushing and screening equipment. (2) To estimate the noise levels from future operations which mining activity is in its closest proximity to adjacent homes. 1.2. Minnesota Noise Standards Noise impacts are evaluated here relative to the Minnesota noise standards for residential land uses, which are presented below in Table 1.1. It is assumed here that both mobile and stationary equipment may operate in one location for at least 30 minutes of an hour, so that daytime L50 standard of 60 dBA is the limit above which exceedances of the standards will occur. This is the most stringent applicable standard. Table 1.1 Minnesota Noise Standards for Residential Land Uses Daytime (7:00 am to 10:00 pm) LIO 65 dBA L50 60 dBA LID is that level exceeded 10% or 6 minutes of an hour. L50 is that level exceeded 50% or 30 minutes of an hour Nighttime (10:00 pm to 7:00 am) 55 dBA 50 dBA 1.3. Organization of this Report Section 2.0 of the report presents assumptions used in this assessment including mine locations and mining activity. Section 3.0 of the report describes noise monitoring that was undertaken on Wednesday, 25 October 2006, before normal mining operations ceased for the calendar year. Section 4.0 presents estimates of noise levels from future mining activity. Potential impacts and mitigation of noise is also discussed. Section 5.0 summarizes the findings and recommendations ofthe study. David Braslau Associates, Inc. Page 1 Tiller Corporation Elk River and Livonia Quarries Noise Assessment 2.0 ASSUMPTIONS ON MINING ACTIVITY To develop quantitative estimates of potential impacts, assumptions as to mining activity within the three quarries must be developed. This section outlines the assumptions that have been used to evaluate noise levels. 2.1. Livonia Mining Operation 2.1.1. 2006 Operations General location of the Livonia Mining Operation adjacent to TH 169 is shown in Figure 2.1. The only residential land use potentially impacted by mining in this area is the Spencer residence identified in the figure at an elevation of approximately 1035 feet. Also shown in the figure are two noise monitoring sites used to help establish existing noise levels. The primary noise sources in this operation (primary crusher and cone/screening) are also shown on the figure. Secondary noise sources are loaders and trucks. The pit floor elevation is approximately 965 feet. Noise monitoring sites are also shown on Figure 2.1. 2.1.2. 2007 and Future Operations In 2007, the primary crusher will move slightly to a new location as shown in Figure 2.2. In the future the cone crusher and screen as well the primary crusher will move towards the north along with the mine face ending at a final location also shown in Figure 2.2. The Spencer residence is assumed to be the closest residential land use adjacent to this operation in the future. The pit floor elevation will remain at approximately 965 feet. 2.2. Elk River Mining Operation 2.2.1. 2006 Operations General location of the Elk River Mining Operation is shown in Figure 2.3. The primary noise source at this location is the crushing complex which includes crushing and screening operations. Secondary noise sources are loaders and trucks. The closest residential receptors are located to the south of the mining crusher complex as seen in the figure. The elevations of the three closest homes range from 1070 to 1098 feet. The pit floor elevation is 990 feet. Noise monitoring sites are also shown on Figure 2.3. David Braslau Associates, Inc. Page 2 @ Spencer monitoring site @ NE corner monitoring site FIGURE 2.1 Livonia Mining Operation - General Location 2006 . I III ~liPll$( t I!'a!llILTDlIWL .... .N ~ [ =~ ~~ . e=-~ ~fW;u;j:Viim ~".<<l(l'.;l,tiMh FIGURE 2.2 Livonia Mining Operation - 2007 and Future Layout @ Monitoring site FIGURE 2.3 Elk River Mining Operation - General Location 2006 Tiller Corporation Elk River and Livonia Ouarries Noise Assessment 2.2.2. 2007 and Future Operations In 2007, it is assumed that the crushing complex will move towards the SSW along with the mine face. The shielding of some noise from the complex by existing topography is assumed to be removed and a berm constructed with a peak elevation of 1110 feet as shown in Figure 2.4. Longer term future operations will shift to a new location on the other side of the road and eventually move towards the SE closer to the homes as shown in Figure 2.4. The pit floor elevation is expected to be 990 feet. 2.3. Elk River Wash Plant Facility 2.3.1. 2006 Operations General location of the Elk River Wash Plant Facility is shown in Figure 2.5. In 2006 the primary noise sources were the shale jig and wash plant. Secondary sources include loaders and trucks. The closest residential receptors are located just west of the recreational trail which runs generally north-south at the west boundary of the wash plant property. These homes range in elevation from 960 to 978 feet. These elevations of the three closest homes range from 1070 to 1098 feet. Elevation of the shale jig is 998 feet while the wash plant is at 999 feet. In 2006, stockpiles up to 40 feet in height were distributed along the west side of the wash plant area, providing some noise shielding of wash plant operations. Noise monitoring sites are also shown on Figure 2.5. 2.3.2. 2007 and Future Operations In 2007, it is assumed that shale jig and wash plant will remain in the 2006 location but the cone crusher from the Livonia Mining Operation will be relocated to this area as shown in Figure 2.6. Upon removal of the stockpiles, an earth berm will be constructed along the west boundary of the wash plant area as shown in Figure 2.6 to provide shielding of the homes to the west. Height of the berm will be discussed below in Section 5.3. David Braslau Associates, Inc. Page 6 FIGURE 2.4 Elk River Mining Operation - 2007 and Future Layout @Trail monitoring site FIGURE 2.5 Elk River Wash Plant Facility - General Location 2006 I ! / I I I , ) \, ( "..-"" ~ ~'~~jJ._...... p~r.r.f ./ .~. ..:t~ ___....J .~ ..::.:~.~. -- -- i , I I .,[.--..-..--- -.'-. -..,/ {J CJ FIGURE 2.6 Elk River Wash Plant Facility - 2007 and Future Layout Tiller Corporation Elk River and Livonia Quarries Noise Assessment 3.0 NOISE MONITORING PROGRAM 3.1. Noise monitoring locations and results Sound levels were monitored on and near the quarries on Wednesday, 25 October 2006. Continuously recording meters were located at the "Spencer site" shown on Figure 2.1 and the "Trail site" show on Figure 2.5. Larson Davis Model 700 Type 2 logging sound level meters were used at these locations to record sound levels during each one minute interval. These data were used to establish the existing ambient noise in two of the most critical sites. Spot sound level spectra were measured at these locations as well as at the NE comer of the Livonia Mining Operation, and at a home south of the Elk River Mining Operation shown on Figure 2.3, using a Casella CEL Model 593 Type I sound level analyzer. Octave Band or One- Third Octave Band data were taken every second for periods ranging from 30 seconds to 2 minutes, depending upon the variability of the noise source being monitored. These readings were used to establish source levels of the processing equipment and loaders, to confirm the continuous readings, and to establish ambient readings in other locations. Sound level readings taken near the mine property lines or off-site are listed in Table 3.1. The other readings were taken in the vicinity of process equipment and used to establish sound source levels for this equipment. Table 3.1 Monitored (L50) Sound Levels (dBA) at Non-Mining Sites Reading Time Location eEL 593 LD700 1/1 Octave 1 14:34 Trail site 45.1 44 2 15:15 Spencer site 47.1 52 3 15:16 Spencer site 49.7 52 8 15:53 NE corner of mine 64.8 11 16:44 Spencer site 51.6 12 16:45 Spencer site 49.2 13 17:03 NE corner (shutdown) 65.2 14 17:13 NE corner (shutdown) 67.3 15 17:25 Spencer site (shutdown) 47.4 50 16 17:50 Trail site (shutdown) 37.8 37 17 18:13 South home site (shutdown) 48.0 1/3 Octave 1 14:39 Trail site 46.3 2 18:15 South home site (shutdown) 46.7 Based upon an analysis of sound levels in the vicinity of mining equipment, the assumed source levels for this assessment are presented in Table 3.2. David Braslau Associates, Inc. Page 10 ----- Tiller Corporation Elk River and Livonia Quarries Noise Assessment Table 3.2 Assumed Sound Level Spectra for Mine Sources (dB at 100 feet) Octave Band Freauencv (Hz) Source 32 63 125 250 500 1000 2000 4000 8000 dBA Livonia Primary 81.2 81.5 83.6 78.9 74.7 72.2 69.0 62.3 52.8 77.8 Livonia Twin Screens 75.3 73.4 78.1 72.8 75.4 77.9 71.9 65.3 59.8 80.3 Elk River processing 79.3 80.2 79.0 78.2 79.2 79.0 74.7 65.1 50.7 82.4 Elk River Shale jig/wash plant 81.4 77.5 82.9 70.8 77.4 71.8 68.0 61.7 57.4 77.7 Loader 79.9 74.2 82.7 78.3 73.4 66.6 70.0 62.0 43.2 76.4 3.2. Comparison of Monitored and Modeled Levels Sound levels at the monitoring sites were also modeled using the source levels in Table 3.2 and the location of mining activity. Locations of monitoring sites and process equipment in 2006 when readings were taken are shown in Figure 2.1, Figure 2.3, and Figure 2.5. The modeling methodology for theoretical prediction of sound levels is discussed in Section 4.0. Table 3.3 compares the monitored and modeled L50 sound levels at each of the affected monitoring sites. Modeled levels refer to an outdoor propagation model for point sources while Road Model refers to predictions using the MinnNoise highway noise model, based upon estimated traffic volumes from the MnDOT traffic flow map for TH 169, and simplified geometry assumptions. Predictions by this model were divided into off-peak (readings #2 and #3 taken close to 3 pm) and other readings taken at 4 pm and later. Table 3.3 Predicted Crusher Complex Sound Levels (dBA) Reading Time Location Road eEL 593 LD 700 Modeled Model Octave 1 14:34 Trail site 45.1 44 62.6 2 15:15 Spencer site 47.1 52 44.2 59.6 3 15:16 Spencer site 49.7 52 44.2 59.6 8 15:53 NE corner of mine 64.8 55.7 67.9 11 16:44 Spencer site 51.6 44.2 62.6 12 16:45 Spencer site 49.2 44.2 62.6 13 17:03 NE corner (shutdown) 65.2 70.9 14 17:13 NE corner (shutdown) 67.3 70.9 15 17:25 Spencer site (shutdown) 47.4 50 62.6 16 17:50 Trail site (shutdown) 37.8 37 17 18:13 South home site (shutdown) 48.0 68.7 1/3 Octave 1 14:39 Trail site 46.3 2 18: 15 South home site (shutdown) 46.7 For readings #1 and #1 (1/3 Octave), the modeled level was well above the monitored level, which is attributed to insufficient shielding assumed by the stockpiles. The data did demonstrate, David Braslau Associates, Inc. Page 11 Tiller Corporation Elk River and Livonia Quarries Noise Assessment however, that with appropriate shielding, the sound level could be kept below the L50 50 dBA nighttime limit. The levels were well below the daytime L50 60 dBA limit. Reading #16 at the Trail site (after shutdown) represents the ambient or background sound and suggests that the shale jig and wash plant increased the sound level by only 7 dBA. Readings #2 and #3 near the Spencer residence were above the modeled levels and were dominated by traffic noise from TH 169 but were still below the daytime and nighttime noise standard, except for an L50 52 reading at the continuous monitor. The modeled road noise level was higher than the observed level due to limited information on road elevation, topography east of TH 169 and actual traffic volumes. The table shows that mining levels were below ambient levels and had little impact on levels at the Spencer site since later readings (#11 and #12 and the post-shutdown reading at 17:50 were essentially unchanged from the earlier readings. This same conclusion can be drawn for readings at the NE comer of the Livonia property (readings #8, #13 and #14) since the pre- and post-shutdown values were essentially the same. At the south home site readings were taken after shutdown (# 17 and #2 (1/3 octave)) and it was not possible to accurately model levels since, while the crushing complex was not operating, some loaders or other mobile equipment not visible from the monitoring site were still operating. David Braslau Associates, Inc. Page 12 Tiller Corporation Elk River and Livonia Quarries Noise Assessment 4.0 PREDICTION 2007 AND FUTURE NOISE LEVELS 4.1. Modeling methodology and assumptions The computer prediction model used takes into account the decay of sound level with distance, atmospheric absorption of sound, shielding by barriers and topography and ground impedance. No additional attenuation from vegetation was assumed in the model since vegetation between mining operations and the closest residential receptor sites is limited and is assumed to have little effect in reducing sound level. The source levels in Table 3.2 which are based upon measurements at know distances from the equipment are assumed in the modeling of existing and future sound levels. The sound source elevation for the primary crushing equipment is assumed to be 12 feet above ground level. The source level for the cone crusher and screens is assumed to be 10 feet above ground level. The source level for the shale jig is also assumed to be 10 feet above ground level, while the loader is assumed to be 8 feet above ground level. In all cases, standard atmospheric conditions and a temperature of 590 F and 70% humidity are assumed. Since distances from equipment to nearby sources are less than 2000 ft, atmospheric absorption does not playa major role. The ground effect portion of the model assumes a slight downwind condition, although this adjustment to sound level is also relatively small. 4.2. Livonia Mining Operation Assumed process equipment locations for 2007 and the future location closest to the Spencer resident are shown on Figure 4.1. The break in topography presented by the perimeter haul road along the easterly and northerly boundaries of the mining area is considered as a topographic barrier for noise from equipment in the pit. As noted in Section 2.1.2 a pit floor elevation of 965 feet is assumed. Predicted L50 levels from each source and the overall L50 level at the Spencer residence in 2007 and in the future when the process equipment is closest to the residence are shown in Table 4.1. Table 4.1 Livonia Mining Operation Sound Levels (L50 in dBA) 2007 Future Spencer residence 46.4 49.9 Primary crusher 42.2 48.2 Cone and screens 41.9 42.4 Loader 40.4 41.2 From Table 4.1, it can be seen the L50 50 dBA level associated mining activity is not expected to be approached at the Spencer residence until the process equipment is moved to the far north boundary of the mining area. Traffic noise from TH 169 is likely 50 dBA or higher during much of the day and will mask noise from the mine. Ifnecessary, a small berm approximately 5 feet in height could be located along the west edge ofthe perimeter haul road to meet the nighttime L50 standard at the Spencer residence when traffic on TH 169 is minimal. However, the operation should be in compliance with the daytime L50 60 dBA level since the predicted levels are 10 dBA below that limit. David Braslau Associates, Inc. Page 13 . ....-.. , .. ,_' 1- ~--.: .. , ~~..._.." t l ~1ill.ZlWlll'.~ ~ ! [ ~~ ~~ . e~~~ ~j'lJ.l(;4~>tM f'{f'_~~_4rt... FIGURE 4.1 Livonia Mining Operation - 2007 and Future Assumptions Tiller Corporation Elk River and Livonia Quarries Noise Assessment 4.3. Elk River Mining Operation Assumed locations of the crushing complex in 2007 (or when this area has been fully mined) and the future location closest to the nearest homes are shown on Figure 4.2. The berm with peak elevation of 1110 feet is shown just north of home sites 2 and 3 in the figure. The break in topography presented by the road along the eastern boundary of the future mining area is considered as a topographic barrier for noise from equipment in the pit. As noted in Section 2.2.2 a pit floor elevation of 990 feet is assumed. The L50 levels at the nearest homes have been estimated for 2007 or the most southerly location of process equipment in the current mining area, and for future locations in the new mining area. Predicted L50 levels from each source and the overall L50 levels at the nearest homes are shown in Table 4.2. Table 4.2 Elk River Mining Operation Sound Levels (L50 in dBA) Time Period - 2007 Home1 43.9 Home2 50.0 Home3 49.5 Process 42.3 Process 48.6 Process 47.9 Loaders 38.9 Loaders 44.7 Loaders 44.3 Time Period - Future (with 10 foot berm aloll roadwav) Home1 49.0 Home2 49.9 Home3 46.0 Process 47.6 Process 48.4 Process 44.3 Loaders 43.4 Loaders 44.7 Loaders 41.0 Time Period - Future (600 ft from closest am roach) Home1 48.4 Home2 50.6 Home3 47.2 Process 47.0 Process 49.3 Process 45.7 Loaders 42.7 Loaders 44.8 Loaders 41.8 The predictions for 2007 assume that the process equipment is as far south as possible within the current mining area. The predicted L50 level is 50.0 dBA at Home2 and 49.5 dBA at Home3. Increasing the proposed berm height from 1110 to 1115 feet should keep the levels below 50 dBA. For process equipment at its most southeasterly location in the new mining area, a 10 foot berm along the west side of the road separating mining from the homes will be needed to keep the L50 level below 50 dBA. With no additional berm, the L50 level in Table 4.2 is slightly over 50 dBA with the equipment located 600 feet to WNW of the closest location (see Figure 4.2). Therefore, to comply with the L50 50 dBA nighttime standard, the equipment would have to be at least 600 feet from the closest approach. For 2007 and the future, sound levels will be well below the L50 60 dBA daytime standard even without a berm along the west side ofthe road. Only nighttime operations will require some additional measures. David Braslau Associates, Inc. Page 15 t~'" ~, 1 [Location to meet ". L50 50 dBA '",/ l\,without berm) FIGURE 4.2 Elk River Mining Operation - 2007 and Future Assumptions Tiller Corporation Elk River and Livonia Quarries Noise Assessment 4.4. Elk River Wash Plant Facility The existing locations of the shale jig and wash plant are shown in Figure 4.3. These will remain the same in 2007 and the future, but, as shown in the figure, will be complemented in 2007 and the future with the relocated cone crusher and screens from the Elk River Mining Operation. An earth berm to replace the stockpiles will be located along the western perimeter of the wash plant and processing area. The berm was initially analyzed with a height of 12 feet above grade but was modified as discussed below to keep the noise at the homes to the west below the L50 50 dBA nighttime standard. As seen from the figure, grade increases generally from the south to a high point of 1001 feet before dropping again to the north. Pre L50 levels by source and the overall L50 level at the nearest homes in 2007 and beyond are shown in Table 4.3. Levels with an opening in the berm are shown to demonstrate the importance of shielding the adjacent homes from process equipment noise. Table 4.3 Elk River Wash Plant Sound Levels (L50 in dBA) Wash Plant - 12 Foot Berm (with onen l!an for vehicle access) Home1 54.7 Home2 57.5 Home3 48.4 Home4 49.6 Jig 53.9 Cone 54.8 Jig 45.2 Jig 46.4 Cone 44.5 Loader 52.8 Cone 42.6 Cone 43.8 Loader 43.8 Jig 48.6 Loader 42.5 Loader 43.5 Wash Plant - 12 Foot Berm (without onen l!al Home1 49.8 Home2 51.8 Home3 48.4 Home4 49.6 Jig 46.5 Jig 48.6 Jig 45.2 Jill 46.4 Cone 44.4 Cone 46.4 Cone 42.6 Cone 43.8 Loader 43.8 Loader 45.6 Loader 42.5 Loader 43.5 Wash Plant - 12 Foot Berm with 21 foot center section and no onen un Home1 48.1 Home2 49.9 Home3 46.7 Home4 49.0 Jig 44.7 Jig 46.6 Jig 43.4 Jig 45.8 Cone 42.5 Cone 44.2 Cone 41.1 Cone 43.1 Loader 42.4 Loader 44.1 Loader 40.8 Loader 43.0 A continuous 12-foot berm will not be sufficient to bring the L50 at Home2 (with the highest elevation) down to 50 dBA. The analysis suggests that constructing a berm with a 21- foot center section will be needed. Even with an opening in the 12-foot berm, however, sound levels will comply with the L50 60 dBA daytime noise standard. Unless homes are constructed south of Home 1, it may be possible to stop the berm approximately 200 feet from the south property line to provide for vehicle access to the west of the berm. Otherwise, a gap can be provided in the berm provided that the gap is shielded on both sides to prevent a direct noise path through the opening. y:\jobs\2006jobs\2061 02\report\tiller _quarries_noise _ assessment.doc David Braslau Associates, Inc. Page 17 I l / I I CJ(1': ,-_/ i \'".l..//) F:,'~rJ / .. .~(. - .' .." l --..-'- ~-~- ~./" ~ 9 300' I FIGURE 4.3 Elk River Wash Plant Facility - 2007 and Future Assumptions Tiller Corporation Elk River and Livonia Quarries Noise Assessment 5.0 SUMMARY OF FINDINGS AND RECOMMENDATIONS 5.1. Sound Levels Associated with 2006 Operations 5.1.1. Livonia Mining Operation Sound levels were monitored near the Livonia Mining Operation and Elk River Wash Plant Facility during mining operations. The monitored sound level at the closest receptor to the Livonia operation (Spencer residence) was generally below 50 dBA, even though the sound level was dominated by noise from traffic on TH 169. Thus, mining operations in 2006 complied with both daytime (L50 60 dBA) and nighttime (L50 50 dBA) state noise standards. The observed level at the northeast corner of the mining operation property was just under 65 dBA during mining operation but was just over 67 dBA after mining shutdown. Thus, noise from mining did not appear to have any significant impact at the northeast corner of the property. 5.1.2. Elk River Mining Operation No readings were taken at the Elk River Mining Operation boundary during operation although a reading taken following (partial) shutdown when some mobile equipment was still operating registered as high as 48 dBA. The monitoring site had some direct exposure to TH 169 which contributed to the ambient level at this location. 5.1.3. Elk River Wash Plant Facility Sound levels on the property line west of the Elk River Wash Plant were as high as 45 dBA during mining operation and 37 dBA after shutdown, suggesting that mining activity increased the level by about 8 dBA. However, the level was below the nighttime L50 50 dBA standard, and well below the daytime L50 60 dBA standard. 5.2. Estimated Sound Levels Associated with 2007 Operations 5.2.1. Livonia Mining Operation At the Livonia Mining Operation, the primary crusher is the loudest piece of equipment. It will remain in essentially the same location, so that 2007 levels will be similar to those in 2006. As noted above, mining activity will have limited impact on the Spencer residence and is estimated to be in compliance with the nighttime and daytime noise standards. 5.2.2. Elk River Mining Operation The sound level associated with the crushing complex at the Elk River Mining Operation will be higher than in 2006 since the equipment will be moved closer to the homes south of the pit. A berm with a peak elevation of 1110 feet will be constructed south of the pit to help reduce sound levels at the nearest homes. A sound level of 50 dBA is estimated at the nearest home and just under 50 dBA at another home. A small increase in the height of the berm could provide additional shielding and allow mining to continue during nighttime hours in compliance with the state noise standard. David Braslau Associates, Inc. Page 19 Tiller Corporation Elk River and Livonia Quarries Noise Assessment 5.2.3. Elk River Wash Plant Facility The large stockpiles shielding homes west ofthe shale jig and wash plant will be replaced in 2007 by a lower earth berm, and addition of the cone crusher and screens will increase the overall source level. In order to maintain compliance with the nighttime sound level at the nearest homes to the west, a berm height of at least 21 feet is recommended for the central portion of the berm which lies between the process equipment and the homes. The south end ofthe berm could be terminated short of the property line to allow vehicle access, or an opening with overlapping berms on either side could also provide vehicle access while maintaining the effectiveness of the berm. 5.3. Estimated Sound Levels Associated with Future Operations 5.3 .1. Livonia Mining Operation At the Livonia Mining Operation, the primary crusher, cone crusher and screens will eventually be located near the north property line of the operation, much closer to the Spencer residence. The estimated sound level at the Spencer residence for this equipment location is 49.9 dBA, just under the L50 50 dBA limit. Placement of a small berm approximately 5 feet in height along the west side of the perimeter haul road would provide additional shielding and allow compliance with the nighttime standard. 5.3 .2. Elk River Mining Operation In the future, the process equipment at the Elk River Mining Operation will be relocated to the west side of the road separating the current and future pits. With processing equipment just west of the nearest homes, a 10 foot berm will be needed along the west side of the road to enable the equipment to operate at night while complying with the nighttime noise standards. If the equipment is to operate at night in compliance with the nighttime standard without an additional berm, the equipment will have to be located at least 600 feet to the WNW of the closest approach shown in Figure 4.2. 5.3.3. Elk River Wash Plant Facility Since the equipment at the Elk River Wash Plant Facility will not change in the future, the sound levels and berm recommendations for 2007 operations will also apply to future operations at this location. 5.4. Concluding Comment The emphasis of this study was an assessment of mining noise relative to the Minnesota nighttime noise standard L50 50 dBA and recommendations to comply with this level. Since the daytime noise standard is 10 dBA higher (L50 60 dBA), compliance with the nighttime standard ensures compliance with the daytime standard. Since none of the monitored levels near the mine in 2006 or predicted level in 2007 and beyond exceeded 60 dBA, the mining operations as planned should be in compliance with the state daytime standards at the existing homes in the vicinity of the mines. y:\jobs\2006jobs\2061 02\report\tiller _quarries_noise _ assessment.doc David Braslau Associates, Inc. Page 20 TILL ORPORATION Tiller Corporation (llId its operating divisiolls Corporate Office: PO Box 1480 7200 Hemlock Lane, Suite 200 Maple Grove, Mimlesota 55311 B.lfton Sand &: Gravel Co. Commercial Asphalt Co. Barton Ellterprises, Inc. general: (763) 425-4191 facsimile: (763) 425-7153 web: www.illlercorp.com February 8, 2007 Rebecca Haug City of Elk River Environmental Administrator 13065 Orono Parkway Elk River, MN 55330 Re: Noise Assessment Dear Ms. Haug: Tiller Corporation (Tiller) and its operating division Barton Sand & Gravel Co. engaged David Braslau Associates Incorporated to conduct a noise assessment (enclosed) of our facilities in the city of Elk River. Among other things, the purpose of the assessment was to (I) monitor noise levels from existing operations relative to Minnesota daytime noise standards, (2) predict noise levels from future operations as equipment moves closer to property boundaries and (3) determine compliance with Minnesota's nighttime noise standards. Following is a brief summary of the assessment. Existin2 Operations Noise levels from equipment that processes and washes sand and gravel was measured near residences closest to the equipment. The noise levels measured show compliance with the allowed state daytime noise standards. Future Operations As operations move toward the boundaries of the facility, equipment may be closer to residences. Modeling was used to predict noise levels at different locations near residences. The predicted noise levels also show compliance with the allowed state daytime noise standards. Compliance witb Ni2bttime Standards The assessment shows that compliance with nighttime noise standards can be achieved with slight modifications to existing conditions. Because Tiller is requesting permission to operate during a time period when nighttime noise standards apply, it is Tiller's intention to This Company is an Equal Opportunity Employer February 8, 2007 Page 2 oi2 fully comply with the recommendations in the assessment. These modifications will be implemented before operating at times when nighttime standards apply. Future Noise Assessments If permission is granted to operate as requested, Tiller will conduct an additional noise assessment to confirm that the recommended modifications are achieving compliance with nighttime noise standards. The results from this assessment will be supplied to City staff. Please contact me if you need more information or clarifications. I may be reached at (763) 315-6004.