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Home My WebLink About0201_AlexanderCDLF_LFGPlan_DIN26614_20160812Landfill Gas Monitoring Plan Prepared for Alexander County Active Construction and Demolition Landfill over/and Closed Unlined Municipal Solid Waste Landfill Taylorsville, North Carolina Permit 0201-CDLF-1997 Prepared by: Municipal Engineering Services Company PO Box 97 Garner, NC 27529 Corporate License Number: C-0281 MESCO Project Number: G16031.0 Submitted: August 11, 2016 This revised plan supersedes all previous approved landfill gas monitoring plans DIN 26614 Approved by SWS August 12, 2016 1 TABLE OF CONTENTS 1 INTRODUCTION 2 1.1 BACKGROUND ................................................................................................................................... 2 1.2 SITE GEOLOGY AND HYDROGEOLOGY ...................................................................................... 2 1.3 REGULATORY LIMITS ..................................................................................................................... 3 2 LANDFILL GAS MONITORING 3 2.1 LANDFILL GAS PROBES .................................................................................................................. 3 2.1.1 LANDFILL GAS PROBE LOCATIONS .................................................................................. 3 2.1.2 LANDFILL GAS PROBE CONSTRUCTION SPECIFICATIONS .......................................... 4 2.2 STRUCTURE MONITORING ............................................................................................................. 4 2.3 LANDFILL GAS MONITORING FREQUENCY ............................................................................... 4 3 LANDFILL GAS SAMPLING PROCEDURE 4 3.1 EQUIPMENT ........................................................................................................................................ 4 3.2 MONITORING PROCEDURE ........................................................................................................... 5 4 RECORD KEEPING AND REPORTING 5 4.1 MONITORING DATA FORM ............................................................................................................. 5 4.2 MONITORING REPORTS ................................................................................................................... 5 4.3 PERMANENT RECORD KEEPING ................................................................................................... 5 5 CONTINGENCY PLAN 6 TABLES LFG MONTORING LOCATION DETAILS …………………………………………………….…..... Table 1 FIGURES POTENTIOMETRIC MAP OF UPPERMOST AQUIFER ………………………………......................Figure 1 LANDFILL GAS MONITORING LOCATIONS ……………………………………..............…..........Figure 2 APPENDICES SWS LANDFILL GAS MONITORING (NOVEMBER 2010)…………………………………..…Appendix A LANDFILL GAS MONITORING DATA FORM (EXAMPLE)…………………………………... Appendix B LANDFILL GAS MONITORING PROBE COMPLETION LOGS ………………………….……Appendix C 2 1 INTRODUCTION 1.1 BACKGROUND North Carolina Solid Waste Management Rules 15A NCAC 13B require quarterly monitoring of methane gas (at MSW landfills) and quarterly monitoring of methane and other explosive landfill gases (LFG) (at C&D and other landfills) to ensure that methane does not exceed the lower explosive limit (LEL) in the soil at the facility property boundary or 25 percent of the lower explosive limit within facility structures. If the concentration exceeds the specified limits, steps must be taken to ensure the protection of public health and a remediation plan must be implemented immediately. A LFG monitoring plan is necessary to ensure that these performance standards are met. LFG monitoring has been performed at this facility on a quarterly basis since at least 1993 in compliance with Rule .1626 (4)(b). The unlined MSW landfill south of the access road was capped with a cohesive cover and passive LFG venting system in 2008. A small-scale active LFG extraction system has been in operation along the northern edge of the closed unlined MSWLF as part of corrective action for volatile organic compounds detected hydraulically upgradient since 2010. The active LFG extraction system has proven to improve water quality and reduce LFG migration through the vadose along the northern property line. This Landfill Gas Monitoring Plan’s objective is to provide clear guidelines and procedures for field personnel when performing explosive gas monitoring. This plan applies to the entire Alexander County Solid Waste Facility located in Taylorsville, NC which consists of a closed unlined MSWLF and an active construction and demolition (C&D) landfill operating under permit 02-01. Facility conditions or unforeseen sampling variables may warrant deviation from standard procedures in which case alternative sampling procedures will conform to the most current NC Solid Waste Section guidelines and industry Standards. This LFG monitoring plan complies with the current version of the NC Solid Waste Section Landfill Gas Monitoring Guidance referenced henceforth as the SWS Guidance Document. 1.2 SITE GEOLOGY AND HYDROGEOLOGY Alexander County is located in the located in the NC Inner Piedmont Belt (Inner Piedmont). The hydrogeologic terrain of the site is one of massive and foliated crystalline rocks mantled by a thick regolith. The subsurface conditions consist of residual soils and partially weathered rock (PWR) which has formed by in-place weathering of the parent bedrock. The residual soils grade with depth into an indistinct transition zone which consists of PWR and saprolite that overlie the underlying bedrock. Neither PWR nor bedrock is suspected to influence LFG migration at this facility since it is beneath the water table at most locations which 3 serves as the lower LFG confining feature. The hydrogeology of the facility is discussed in greater detail in the Assessment of Corrective Measures (ACM) and Corrective Action Plan (CAP) previously submitted to the SWS under separate cover. The uppermost aquifer across the site has been identified to be generally within the unconsolidated regolith. The vertical LFG migration potential extent is the water table which ranges from approximately 0 to 49 feet below ground. Groundwater generally mirrors topography and a potentiometric map of the uppermost aquifer from groundwater elevations recorded in January 2016 is shown on Figure 1. Per the SWS Guidance Document, subsurface gas typically migrates above the groundwater table and is restricted laterally by streams. Perennial streams are located southeast and northwest of the landfill which decreases the potential for LFG migration beyond Alexander County’s property boundaries. 1.3 REGULATORY LIMITS In accordance with Rule 15A NCAC 13B LFG readings will be recorded quarterly and results will be kept in the facility operating records. Alexander County will follow all operational requirements for MSWLF facilities; ensuring the measured concentrations of methane gas does not exceed the lower explosive limit (100% LEL or 5% by volume) at the facility boundary and (25% LEL or 1.25% by volume) in structures. Hydrogen sulfide gas should not exceed the lower explosive limit (100% LEL or 4.00% by volume) at the facility boundary and (25% LEL or 1% by volume) in structures. LFG records will be submitted to the SWS in the event that stabilized methane or hydrogen sulfide levels exceed these limits or upon SWS request. 2 LANDFILL GAS MONITORING 2.1 LANDFILL GAS PROBES 2.1.1 LANDFILL GAS PROBE LOCATIONS Alexander County Landfill facility located in Taylorsville, NC consists of two waste units. An active construction and demolition (C&D) landfill vertical expansion atop an unlined landfill and a closed sanitary landfill. LFG migration has been monitored by a network of probes and within structures surrounding each unit. A comprehensive facility wide color-coded drawing with an embedded table detailing the LFG monitoring locations is shown on Figure 2. The locations of monitoring points in this new LFG monitoring plan were chosen following careful consideration of spatial relationship between property boundaries and both on and off-site structures. 4 Active CDLF and closed unlined landfill units shall be monitored by 5 existing LFG probes (MP-1, MP-A, MP-B, MP-C and MP-D). Monitoring probe MP-1 monitors along the northeast property boundary, MP-A monitors the eastern property boundary, MP-B monitors south of the landfill, MP-C monitors beyond the northwest portion of the landfill and MP-D monitors the area north of the landfill. Five on-site structures will also be monitored as described in Section 2.2 No additional monitoring locations are currently proposed at the site. 2.1.2 LANDFILL GAS PROBE CONSTRUCTION SPECIFICATIONS Details of the existing LFG probe construction are shown on Table 1 and Appendix C. New probes are not proposed to be installed. All probes will be equipped with a stopcock ball valve bushed to the well casing, quick connect coupling threaded into the well cap or an equivalent device that allows air flow to be controlled at the wellhead as shown on Figure 3. 2.2 STRUCTURE MONITORING The inside of five on-site non-residential (restricted use) structures (OFFICE 1, SCALEHOUSE, SHOP, TS, and TS OFFICE) will be monitored quarterly for LFG accumulation in accordance with the Guidance Document. If new on-site structures are erected in the future they will be monitored along with the existing ones. All on-site structures are detailed on Figures 1 & 2 and Table 1. 2.3 LANDFILL GAS MONITORING FREQUENCY LFG monitoring will be performed and documented on at least a quarterly basis (four times annually approximately three months apart). Monitoring frequency will not be decreased without pre-authorization by the SWS. 3 LANDFILL GAS SAMPLING PROCEDURE 3.1 EQUIPMENT Instrumentation must be capable of accurately reading percent methane, percent hydrogen sulfide, percent oxygen and percent carbon dioxide. Instruments shall be calibrated according to manufacturer’s specifications prior to performing monitoring. Although other instrument(s) maybe available which meet or exceed these requirements that would also be deemed acceptable the most common instrument is a Landfill Gas Analyzer manufactured by LANDTEC which includes models such as GEM500, GEM2000 and GEM5000. Stopcock valves on monitoring probes should remain in a closed position until instrument tubing is tightly sealed. 5 3.2 MONITORING PROCEDURE LFG monitoring will be performed by personnel that understand the principles of operation and use instruments per manufacturer’s instructions. LFG monitoring shall be performed in accordance with procedures outlined in the most current NC SWS issued Landfill Gas Monitoring Guidance Document. A copy of the current SWS Guidance Document dated November 2010 is included in Appendix A. Deviation from procedures outlined in this plan may be warranted depending on facility conditions or unforeseen variables. Any variance from the methodology contained in the current SWS Guidance Document will be consistent with industry standards and be described in the associated LFG monitoring report. 4 RECORD KEEPING AND REPORTING 4.1 MONITORING DATA FORM LFG monitoring event results shall be recorded on a Landfill Gas Monitoring Data Form. The monitoring data form should contain at least the information outlined in the SWS Guidance Document as shown on the example form in Appendix B. 4.2 MONITORING REPORTS A landfill gas monitoring report consisting of at a minimum the completed Landfill Gas Monitoring Report Form and a site drawing showing the location of each monitoring location shall be drafted shortly following every quarterly monitoring event. 4.3 PERMANENT RECORD KEEPING Landfill gas monitoring records including monitoring plans, monitoring reports and remediation plans will be retained at the facility in an operating record and updated as the information becomes available. Reports will be sent to the SWS only in the event methane or hydrogen sulfide is detected above allowable limits or per request. 6 5 CONTINGENCY PLAN If stabilized methane or hydrogen sulfide levels are detected above regulatory compliance levels, additional probe(s) will be installed closer towards the property boundary in order to determine the LFG extent. If stabilized methane or hydrogen sulfide readings are detected above regulatory limits at the facility boundary remedial actions will be implemented per Rule 15A NCAC 13B .1626(4)(c). The specific remedial actions taken to abate LFG migration will be chosen based on site specific circumstances and consistent with industry protocols. In the event facility conditions change which may hinder the effectiveness of this monitoring plan including but not limited to property relinquishment or construction of structures the plan will be revised and the SWS notified. Tables Table 1: Existing Landfill Gas Monitoring Location Details Top Bottom MP-A Probe Unlined and C&D 1363998.4100 766538.0400 2 6 6 Silty Sand MP-B Probe Unlined and C&D 1362839.9200 765304.5900 2 8.8 >10 Silty Sand MP-C Probe Unlined and C&D 1361934.5700 766716.9800 2 7 8 Silty Sand MP-D Probe Unlined and C&D 1362713.2500 767218.4200 2 9 ~37 Clayey Silt MP-1 Probe Unlined and C&D 1363388.7100 767124.9900 2 7.5 ~38 Silty Sand OFFICE 1 Structure Unlined and C&D 1363272.1300 767031.8000 --18 - SCALEHOUSE Structure Unlined and C&D 1363278.2600 766997.4700 --21 - TS Structure Unlined and C&D 1362378.7700 765965.1800 --17 - TS OFFICE Structure Unlined and C&D 1362334.8600 765990.1100 --21 - SHOP Structure Unlined and C&D 1363175.7900 766849.0900 --21 - Information compiled from prior hydrogeologic investigations, well construction records and field measurements. LFG Monitoring Location ID Sand Interval Exposed to LFG (ft BGS) Depth to Groundwater (ft BGS) Predominant Screened Lithology Monitored UnitType Northing Easting Figures OR Equivalent Figure 3 Ball Valve Quick Connect Coupling (Threaded into Cap) (Bushed onto Well Casing) Well Well Instrument Instrument Stop-Cock Valve Construction Details Keep Closed Between Events OR Appendix A SWS Landfill Gas Monitoring Guidance Document (Intended to be most recent version) 1 NORTH CAROLINA DEPARTMENT OF ENVIRONMENT AND NATURAL RESOURCES DIVISION OF WASTE MANAGEMENT SOLID WASTE SECTION LANDFILL GAS MONITORING GUIDANCE NOVEMBER 2010 TABLE OF CONTENTS Section 1 – Introduction ………………………………………………………...............................Page 2 Section 2 – Factors Influencing Landfill Gas Generation and Migration …………………………Page 3 Section 3 - Current Solid Waste Section Rules Pertaining to Landfill Gas Monitoring ……….….Page 5 Section 4 – Landfill Gas Incidents and Explosions ………………………………………………..Page 9 Section 5 – Landfill Gas Monitoring Wells……………..………………………………………….Page 11 Section 6 – Landfill Gas Monitoring Instrumentation ……………………………………………..Page 14 Section 7 – References ……………………………………………………………………………..Page 17 Section 8 – Suggested Outline for a Landfill Gas Monitoring Plan ………………………………..Page 18 Section 9 – Checklist of Items to be Included in a Landfill Gas Monitoring Plan ………………....Page 19 2 SECTION 1 - Introduction North Carolina Solid Waste Management Rules 15A NCAC 13B require quarterly monitoring of methane gas (at MSW landfills) and quarterly monitoring of methane and other explosive landfill gases (LFG) (at C&D and other landfills) to ensure that landfill gas does not exceed the lower explosive limit (LEL) at the facility property boundary or 25 percent of the lower explosive limit in facility structures. If the concentration exceeds the specified limits, steps must be taken to ensure the protection of public health and a remediation plan must be implemented immediately. A landfill gas monitoring plan is necessary to ensure that these performance standards are met and this guidance document was developed to assist in establishing a standardized procedure for the monitoring of landfill gas. Background Organic matter in landfills begins to decompose almost immediately after being placed in a disposal site. Putrescible wastes such as food products and sewage sludges begin to break down by biological processes very rapidly whereas paper, cardboard or cellulose based materials are slower to decompose. However, when conditions become favorable, most organic matter will decompose. The decomposition process typically goes through several stages that depend on conditions such as pH, temperature, and moisture content. The final stage results in the production of methane and although the rate of production may vary, most landfills produce methane. Landfill Gas Generation Landfill gas is a natural by-product of the anaerobic decomposition of organic waste in a landfill. The composition, quantity and rate of landfill gas generation are dependent on the types of waste that are decomposing and the level of microbial activity within the wastes. The decomposition of biodegradable waste begins with aerobic decomposition which lasts until the oxygen in the landfill is depleted. The anaerobic phase then begins, resulting in landfill gas production. There are four stages of landfill gas composition: the first stage is characterized by elevated nitrogen levels and occurs when the landfill is new. The second stage is characterized by elevated carbon dioxide levels and occurs for a relatively short period of time after the initial stage is complete. The third and fourth stages are characterized by elevated methane concentrations and represent the active life of a landfill and the post-closure time frame. Landfill gas is generally composed of 50-55% methane (CH4); 45-50% carbon dioxide (CO2); less than 5% nitrogen (N2); and less than 1% non-methane organic compounds. These individual gases generally remain co-mingled and do not naturally separate. The Solid Waste Section (SWS) Rules typically focus on methane (CH4) and its explosive properties due to public safety issues. Hydrogen sulfide (H2S) is also of particular concern in landfills and is typically recognized by its rotten egg odor. H2S is immediately dangerous to life and health at concentrations of 100 parts per million (ppm). Landfill Gas Migration The production of landfill gas creates a positive pressure within the landfill that forces the gas to migrate. Landfill gas migrates from place to place by diffusion and pressure gradient and will follow the path of least resistance. Subsurface gas typically migrates above the groundwater table and is restricted laterally by streams. Porous soils lying above the bedrock can serve as pathways to transmit large volumes of gas. Underground off-site migration is common and can be facilitated by the presence of pipelines, buried utility corridors or trenches located within or adjacent to the landfill boundaries. Movement depends on soil type and moisture, and migration distances of 1,500 feet have been observed. Barometric pressure also influences movement. Falling barometric pressure allows methane to migrate out of the landfill and into surrounding areas. 3 SECTION 2 - Factors Influencing Landfill Gas Generation and Migration Factors that affect landfill gas generation and migration through the subsurface include the following: Waste Composition The production of landfill gas is directly related to the amount of organic matter present in waste. The bacteria that break down the waste require small amounts of specific minerals such as calcium, potassium, magnesium and other micronutrients. Bacteria are able to thrive and produce landfill gas if the minerals/micronutrients are present. If the minerals/micronutrients are not present or if substances that inhibit bacterial growth exist, landfill gas production will occur at a reduced rate. Some forms of organic matter such as cellulose break down quickly whereas matter such as lignin breaks down more slowly. The rate at which landfill gas is produced depends on the proportions of each type of organic matter present in the waste. Moisture Content Landfills with higher moisture content generate higher concentrations of landfill gas in earlier stages of development (such as during leachate recirculation). Moisture accelerates the methanogenic process. Temperature Landfill bacteria are temperature dependant. They are able to survive and function below the freezing point, but they also function well at temperatures up to 65°C. Anaerobic bacteria produce small amounts of heat and may not be able to maintain the temperature of a shallow landfill when external temperatures decrease, so LFG generation may exhibit seasonal variations. Saturated landfills may not achieve ideal temperatures because the bacteria do not generate sufficient heat to raise the temperature of the excess water. Higher temperatures promote volatilization and chemical reactions with the waste so the trace gas component of landfill gas tends to increase with higher landfill temperatures. Age of Landfill Typically, landfills have an increasing generation of landfill gas for a number of years until closure at which time landfill gas generation reaches a peak and begins to subside. An evaluation of the age of the landfill and use of a landfill gas generation curve can be helpful in determining the likelihood of significant landfill gas concentrations from the landfill. Landfill Cap The type or presence of landfill cover can influence landfill gas generation and migration. Although a low permeability cap will reduce moisture and landfill gas generation over the longer term, initially, the installation of a landfill cap could drive landfill gas migration further from the landfill in the subsurface without proper ventilation (either passive or active). This is especially true in the case of unlined (unvented) landfills. Water Table Landfill gas movement in unlined landfills may be influenced by groundwater table variations. A rising water table could cause displacement and force upward movement of landfill gas. 4 Man-made and Natural Conduits Structures such as drains, trenches, and buried utility corridors can act as conduits for landfill gas migration. Geologic features including fractured bedrock, porous soil, and permeable strata also provide conduits for landfill gas migration Landfill Liner Conditions The presence of a Subtitle-D (or equivalent) landfill liner has the capability to limit the lateral migration of landfill gas in the subsurface. Unlined landfills have no barrier to prevent lateral landfill gas migration in the subsurface. Weather Conditions Barometric pressure and precipitation have significant effects on landfill gas migration. Increased barometric pressure yields decreased landfill gas venting from the subsurface, until the pressure within the subsurface is greater than the atmospheric (barometric) pressure. Conversely, as the barometric pressure decreases, the landfill will vent the stored gas until pressure equilibrium is reached. Capping of a landfill can influence the effect of barometric pressure on landfill gas migration. Generally, a more permeable landfill cap will allow greater influence by barometric pressure than a less permeable landfill cap. 5 SECTION 3 – Current Solid Waste Section Rules Pertaining to Landfill Gas Monitoring Web link to the 15A NCAC 13B rules - http://portal.ncdenr.org/web/wm/sw/rules 15A NCAC 13B .0101- DEFINITIONS .0101 (14) "Explosive gas" means Methane (CH4) .0101(25) "Lower explosive limit" (LEL) means the lowest percent by volume of a mixture of explosive gases which will propagate a flame in air at 25 degrees Celsius and atmospheric pressure. .0503 - SITING AND DESIGN REQUIREMENTS FOR DISPOSAL FACILITIES .0503(2) A site shall meet the following design requirements: (a) The concentration of explosive gases generated by the site shall not exceed: (i) twenty-five percent of the limit for the gases in site structures (excluding gas control or recovery system components); and (ii) the lower explosive limit for the gases at the property boundary; .0543 - CLOSURE AND POST-CLOSURE REQUIREMENTS FOR C&DLF FACILITIES .0543(e) Post-closure criteria. (1) Following closure of each C&DLF unit, the owner and operator must conduct post-closure care. Postclosure care must be conducted for 30 years, except as provided under Subparagraph (2) of this Paragraph, and consist of at least the following: (C) maintaining and operating the gas monitoring system in accordance with the requirements of Rule .0544 of this Section; and (2) The length of the post-closure care period may be: (A) decreased by the Division if the owner or operator demonstrates that the reduced period is sufficient to protect human health and the environment and this demonstration is approved by the Division; or (B) increased by the Division if the Division determines that the lengthened period is necessary to protect human health and the environment. .0544 - MONITORING PLANS AND REQUIREMENTS FOR C&DLF FACILITIES .0544(d) Gas Control Plan (1) Owners and operators of all C&DLF units must ensure that: (A) the concentration of methane gas or other explosive gases generated by the facility does not exceed 25 percent of the lower explosive limit in on-site facility structures (excluding gas control or recovery system components); (B) the concentration of methane gas or other explosive gases does not exceed the lower explosive limit for methane or other explosive gases at the facility property boundary; and (C) the facility does not release methane gas or other explosive gases in any concentration that can be detected in offsite structures. (2) Owners and operators of all C&DLF units must implement a routine methane monitoring program to ensure that the standards of this Paragraph are met. (A) The type of monitoring must be determined based on soil conditions, the Hydrogeologic conditions under and surrounding the facility, hydraulic conditions on and surrounding the facility, the location of facility structures and property boundaries, and the location of all offsite structures adjacent to property boundaries. 6 (B) The frequency of monitoring shall be quarterly or as approved by the Division. (3) If methane or explosive gas levels exceeding the limits specified in Subparagraph (d)(1) of this Rule are detected, the owner and operator must: (A) immediately take all steps necessary to ensure protection of human health and notify the Division; (B) within seven days of detection, place in the operating record the methane or explosive gas levels detected and a description of the steps taken to protect human health; and (C) within 60 days of detection, implement a remediation plan for the methane or explosive gas releases, place a copy of the plan in the operating record, and notify the Division that the plan has been implemented. The plan must describe the nature and extent of the problem and the proposed remedy. (4) Based on the need for an extension demonstrated by the operator, the Division may establish alternative schedules for demonstrating compliance with Parts (3)(B) and (3)(C) of this Paragraph. (5) For purposes of this Item, "lower explosive limit" means the lowest percent by volume of a mixture of explosive gases in air that will propagate a flame at 25 C and atmospheric pressure. .0566 - OPERATIONAL REQUIREMENTS FOR LAND CLEARING/INERT DEBRIS (LCID) LANDFILLS .0566(13) The concentration of explosive gases generated by the facility shall not exceed: (a) Twenty-five percent of the lower explosive limit for the gases in facility structures. (b) The lower explosive limit for the gases at the property boundary. .1626 – OPERATIONAL REQUIREMENTS FOR MSWLF FACILITIES .1626(4) Explosive gases control. (a) Owners or operators of all MSWLF units must ensure that: (i) The concentration of methane gas generated by the facility does not exceed 25 percent of the lower explosive limit for methane in facility structures (excluding gas control or recovery system components); and (ii) The concentration of methane gas does not exceed the lower explosive limit for methane at the facility property boundary. (b) Owners or operators of all MSWLF units must implement a routine methane monitoring program to ensure that the standards of (4)(a) are met. A permanent monitoring system shall be constructed on or before October 9, 1994. A temporary monitoring system shall be used prior to construction of the permanent system. (i) The type and frequency of monitoring must be determined based on the following factors: (A) Soil conditions; (B) The hydrogeologic conditions surrounding the facility; (C) The hydraulic conditions surrounding the facility; and (D) The location of facility structures and property boundaries. (ii) The minimum frequency of monitoring shall be quarterly. (c) If methane gas levels exceeding the limits specified in (4)(a) are detected, the owner or operator must: (i) Immediately take all necessary steps to ensure protection of human health and notify the Division; (ii) Within seven days of detection, place in the operating record the methane gas levels detected and a description of the steps taken to protect human health; and (iii) Within 60 days of detection, implement a remediation plan for the methane gas releases, place a copy of the plan in the operating record, and notify the Division that the 7 plan has been implemented. The plan shall describe the nature and extent of the problem and the proposed remedy. (iv) Based on the need for an extension demonstrated by the operator, the Division may establish alternative schedules for demonstrating compliance with (4)(c)(ii) and (iii) of this Rule. (d) For purposes of this Item, "lower explosive limit" means the lowest percent by volume of a mixture of explosive gases in air that will propagate a flame at 25°C and atmospheric pressure. .1626(10) Recordkeeping requirements. (a) The owner or operator of a MSWLF unit must record and retain at the facility, or an alternative location near the facility approved by the Division, in an operating record the following information as it becomes available: (iii) Gas monitoring results and any remediation plans required by Item (4) of this Rule; .1627 – CLOSURE AND POST CLOSURE REQUIREMENTS FOR MSWLF ACTIVITES .1627(d) Post-Closure Criteria (1) Following closure of each MSWLF unit, the owner or operator shall conduct post-closure care. Post-closure care shall be conducted for 30 years, except as provided under Subparagraph (2) of this Paragraph, and consist of at least the following: (D)-Maintaining and operating the gas monitoring system in accordance with the requirements of Rule .1626 of this Section. (2) The length of the post-closure care period may be: (A) Decreased by the Division if the owner or operator demonstrates that the reduced period is sufficient to protect human health and the environment and this demonstration is approved by the Division; or (B) Increased by the Division if the Division determines that the lengthened period is necessary to protect human health and the environment. (3) Following completion of the post-closure care period for each MSWLF unit, the owner or operator shall notify the Division that a certification, signed by a registered professional engineer, verifying that post-closure care has been completed in accordance with the post-closure plan, has been placed in the operating record. NOTES: Based on the referenced rules above, the following words / phrases are presently in the Solid Waste Section rules pertaining to methane and explosive landfill gas. Rule .0101(14) states: “Explosive gas means Methane (CH)”. Rule .0503 (2)(a) refers to “explosive gases”. Rule .0544(d) refers to “Gas Control Plan” Rule .0544(d)(1) refers to “methane or other explosive gases”. Rule .0544(d)(2) refers to “methane monitoring program” Rule .0544(d)(3) refers to “methane or explosive gas levels” Rule .0566 (13) refers to “explosive gases”. Rule .1626 (4) refers to “explosive gases control” Rule .1626(4)(a-b) refers to “methane monitoring” and “methane monitoring program”. 8 Monitoring Goals Landfill design and landfill gas monitoring regulations in North Carolina require that there not be an exceedance of 100% of the Lower Explosion Limit (LEL) (equivalent to 5% methane) at the property boundary, or 25% LEL in on-site structures. These regulations were developed over time to protect the health and safety of the citizens of North Carolina and the U.S. from the asphyxiation and explosive hazards of landfill gas. NC Rule History A review of NC landfill guidance documents and regulations from 1972 to the present indicates that from 1972 through 1982, there was no mention of design requirements regarding the control of landfill gas, nor were there any landfill monitoring requirements for landfill gas. In 1982, the regulations were changed to require that sanitary landfill design prevent landfill gas concentrations of 100% LEL at the property boundary line and 25% inside on-site structures. Although a design requirement was added, no design requirement was established to determine if the design requirement was being met. In 1993 with the establishment of .1600 rules, requirements for designs to limit landfill gas levels to below 100% at the property boundary line and 25% in on-site structures and monitoring of landfill gas concentrations around the perimeter of the landfill and inside on-site structures were adopted. 9 SECTION 4 – Landfill Gas Incidents and Explosions Hazards Involving Landfill Gas Landfill fires may or may not be directly caused by landfill gas. The primary concern with these fires is air contamination from the resulting smoke; however they also present a variety of additional problems. In addition to concerns with containing and extinguishing landfill fires, potential reactions involving unknown chemicals in the landfill can cause uncertain hazards. Discarded consumer products in a landfill, such as pesticides, paints, solvents, cleaners, and other material can be the source of chemical releases. Heat from the fire can cause chemicals to volatilize, breakdown, and enter the environment. Also to be considered is the presence of other combustible gases in addition to methane. Whenever an environmental investigation of a landfill is prompted by odorous compounds or explosive gases, the presence of toxic substances should also be investigated. One example is hydrogen sulfide (H2S) that can cause asphyxiation and is flammable. An analysis should include alkyl benzenes, sulfur compounds, vinyl chloride, and methane, and other products associated with industrial wastes, construction and debris waste, and normal organic and inorganic waste. Fires and explosion hazards become a concern when gases collect in confined spaces. Buildings, basements, and pits are typically regarded as confined spaces. However, landfill gases also collect in and migrate to cracks in the landfill cover, leachate “springs”, cracks in adjacent structures, paved parking areas, etc. Fires can occur on the surface and underground. Surface fires involve recently buried waste near the surface in an aerobic decomposing layer, typically 1 to 4 feet below ground. These fires can be intensified by subsurface landfill gas and spread throughout the landfill. Subsurface fires occur deeper within the landfill, involve material buried for months or years, and can burn for days and months. The following is a brief summary of some incidents involving landfill gas migration from landfills: 2007 Four employees died as a result of exposure to high concentrations of hydrogen sulfide while attempting to repair a leachate pump at a C&D landfill in Superior, Wisconsin (Journal of Environmental Heath 2008). 1999 An 8-year old girl was burned on her arms and legs when playing in an Atlanta, Georgia playground. The area was reportedly used as an illegal dumping ground many years ago (Atlanta Journal-Constitution 1999). 1994 While playing soccer in a park built over an old landfill in Charlotte, North Carolina, a woman was seriously burned by a methane explosion (Charlotte Observer 1994). 1987 Offsite landfill gas migration is suspected to have caused a house to explode in Pittsburgh, Pennsylvania (EPA 1991). 1984 Landfill gas migrated to and destroyed one house near a landfill in Akron, Ohio. Ten houses were temporarily evacuated (EPA 1991). 1983 An explosion destroyed a residence across the street from a landfill in Cincinnati, Ohio. Minor injuries were reported (EPA 1991). 1975 In Sheridan, Colorado, landfill gas accumulated in a storm drain pipe that ran through a landfill. An explosion occurred when several children playing in the pipe lit a candle, resulting in serious injury. 10 1969 Methane gas migrated from an adjacent landfill into the basement of an armory in Winston-Salem, North Carolina. A lit cigarette caused the gas to explode, killing three men and seriously injuring five others (USACE 1984). 11 SECTION 5 - Landfill Gas Monitoring Wells Locations Landfill gas monitoring well locations will be site specific depending upon site geology, depth to groundwater, surface water features, on-site and off-site structures and sensitive receptors. The landfill gas monitoring wells must be spaced no more than 500 feet apart depending upon site specifics. A readily accessible, unobstructed path must be maintained so that landfill gas monitoring wells are always accessible using four-wheel drive vehicles. Regardless of site specifics, the permittee must obtain approval from the Solid Waste Section for the design and installation of any landfill gas monitoring well system. Well Construction and Installation Landfill gas monitoring wells are the same as groundwater monitoring wells with two exceptions. Landfill gas monitoring wells are installed just above the water table within the unsaturated zone and are equipped with a stopcock valve or a quick connect coupling on the cap, which allows for accurate landfill gas measurements. The stopcock valve must be equipped with flexible tubing and a barb connection that will fit the gas meter’s inlet tube. The stopcock valve or a quick connect coupling must be closed between monitoring events. The landfill gas monitoring well must also be capped, locked, and labeled with a permanently affixed identification plate stating the well contractor name and certification number, date of well competition, total depth of well, screen length and well ID number. See detailed schematics of a landfill gas monitoring well (Figure 1). The depth of each landfill gas monitoring well will be site specific depending upon depth to groundwater. Landfill gas monitoring wells must be constructed the same as groundwater monitoring wells as described in 15A NCAC Subchapter 2C. Typically landfill gas monitoring wells must be installed using 2” PVC piping and screen. The screen length, also site specific, must span the majority of the unsaturated zone while still allowing for proper well construction. A North Carolina Licensed/Professional Geologist must be present to supervise the installation of all landfill gas monitoring wells. The exact locations, screened intervals, and nesting of the wells must be approved by the Solid Waste Section Hydrogeologist prior to landfill gas monitoring well installation. Each landfill gas monitoring well must be surveyed for location and elevation by a North Carolina Registered Land Surveyor. Within thirty (30) days of the completed construction of each new landfill gas monitoring well, the well construction record (Division of Water Quality form GW-1b) and the boring log/well detail diagram of each well must be submitted to the Solid Waste Section. The submittal must also include a scaled topographic map showing the location and identification of new, existing and abandoned landfill gas monitoring wells. Nested and Clustered Landfill Gas Monitoring Wells Nested and/or clustered landfill gas monitoring wells may be required in unsaturated zones of 45 feet or more to measure specific depths of the unsaturated zone. Initially, the installation of one long screen shall be sufficient. If a monitoring event shows an exceedance of the lower explosive limit, then the Solid Waste Section may require the installation of nested and/or clustered landfill gas monitoring wells. Abandonment of Wells An abandonment record must be submitted to the Solid Waste Section within 30 (thirty) days of the abandonment of a landfill gas monitoring well. The landfill gas monitoring well(s) must be overdrilled and sealed with grout in accordance with 15A NCAC 2C .0113(d) and certified by a North Carolina Licensed/Professional Geologist. 12 Professional Certification The certification statement below must be signed and sealed by a Professional Geologist and submitted with the Landfill Gas Monitoring Plan. The landfill gas monitoring plan for this facility has been prepared by a qualified geologist who is licensed to practice in the State of North Carolina. The plan has been prepared based on first-hand knowledge of site conditions and familiarity with North Carolina solid waste rules and industry standard protocol. This certification is made in accordance with North Carolina Solid Waste Regulations, indicating this Landfill Gas Monitoring Plan should provide early detection of any release of hazardous constituents to the uppermost aquifer, so as to be protective of public health and the environment. No other warranties, expressed or implied, are made. Signed _______________________________ Printed _______________________________ Date _________________________________ Not valid unless this document bears the seal of the above mentioned licensed professional. 13 Figure 1 – Landfill Gas Monitoring Well Detail 14 SECTION 6 – Landfill Gas Monitoring Instrumentation The person using the landfill gas monitoring instrument must understand the principles of operation and follow the manufacturer's instructions. This includes calibrating the instrument according to the manufacturer’s specifications. Include the following on the top portion of the landfill gas monitoring form (See example below) : facility name, permit number, type and serial number of gas monitoring instrument, calibration date of the instrument, date and time of field calibration, type of gas used for field calibration (15/15 or 35/50), expiration date of field calibration gas canister, date of landfill gas monitoring event, name and position of sample collector, pump rate of instrument being used, ambient air temperature, and general weather conditions. Verification that the equipment was calibrated in accordance with the manufacturer’s specifications is also required. When determining which field calibration gas to use, take into consideration the expected levels of methane in the landfill gas monitoring wells. If the methane levels are expected to be low, use the 15/15 gas canister (15% CO2/15% CH4). If the methane levels are expected to be high, use the 35/50 gas canister (35% CO2/50% CH4). For every landfill gas monitoring well, please include the following: verification of sample tube purge prior to each sample taken (should be one minute), the time pumped in seconds (should be at least one minute), barometric pressure, time stabilized reading collected, percent lower explosive limit, percent methane by volume, percent oxygen, percent carbon dioxide, and any observations or comments. Most modern gas monitoring instruments will measure percent oxygen and carbon dioxide in addition to the methane and display the results on the same instrument. Recording the levels of percent oxygen and carbon dioxide should require little or no extra effort. The landfill gas monitoring data form (See example below) and results should be retained in the facility’s operating record unless an exceedance has occurred and/or is requested by the Solid Waste Section. Landfill gas monitoring readings from non-calibrated or inaccurately calibrated instruments are not reliable, and will therefore be rejected by the Solid Waste Section. Landfill gas monitoring readings collected with monitoring equipment that was not designed for landfill gas monitoring will also be rejected by the Solid Waste Section. There are several different landfill gas monitoring instruments on the market which may be used in order to obtain all of the information required by the Solid Waste Section. Monitoring Times Monitoring times are also important when conducting landfill gas monitoring. Proper landfill gas monitoring should include sampling during times when landfill gas is most likely to migrate. Landfill gas can migrate and accumulate not only in landfill gas monitoring wells; it can also migrate and accumulate in buildings and other structures. Because subsurface gas pressures are considered to be at a maximum during the afternoon hours, monitoring should be conducted in the afternoon or whenever the barometric pressure is low. Scientific evidence also indicates that weather and soil conditions influence the migration of landfill gas. Barometric pressure and precipitation have significant effects on landfill gas migration. Increased barometric pressure generates decreased landfill gas venting from the subsurface, until the pressure within the subsurface is greater than the atmospheric (barometric) pressure. On the other hand, when the barometric pressure decreases, the landfill will vent the stored gas until a pressure equilibrium is reached. Capping of a landfill can influence the effect of barometric pressure on landfill gas migration. Generally, a more permeable landfill cap will allow greater influence by barometric pressure than a less permeable 15 landfill cap. As a result, landfill gas monitoring should be conducted when the barometric pressure is low and soils are saturated. During the winter season when snow cover is just beginning to melt or when the ground is frozen or ice covered, landfill gas monitoring should be conducted when the barometric pressure is low. Landfill Gas Sampling Procedures Any accumulation of landfill gas in the landfill gas monitoring wells is the result of landfill gas migration. The following procedure is a recommended example for conducting landfill gas monitoring well sampling, but always read and follow the manufacturer’s instructions because each instrument will be different. Step 1 – Calibrate the instrument according to the manufacturer’s specifications. In addition, prepare the instrument for monitoring by allowing it to properly warm up as directed by the manufacturer. Make sure the static pressure shows a reading of zero on the instrument prior to taking the first sample. Step 2 – Purge sample tube for at least one minute prior to taking reading. Connect the instrument tubing to the landfill gas monitoring well cap fitted with a stopcock valve or quick connect coupling. Step 3 – Open the valve and record the initial reading and then the stabilized reading. A stable reading is one that does not vary more than 0.5 percent by volume on the instrument’s scale. Step 4 - Record the stabilized reading including the oxygen concentration and barometric pressure. A proper reading should have two percent oxygen by volume or less. If levels of oxygen are higher, it may indicate that air is being drawn into the system giving a false reading. Step 5 – Turn the stopcock valve to the off position and disconnect the tubing. Step 6 – Proceed to the next landfill gas monitoring well and repeat Steps 2 – 5. Landfill Gas Constituent Sampling and Analysis Sampling of landfill gas to determine volume percentages/concentrations of each constituent can be accomplished through the use of canisters which are specifically designed for landfill gas analysis. Several analytical methods are available to determine the concentrations of a variety of constituents. Typically, landfill gas analysis of this type is performed to determine the non-methane organic compounds emission rate for Tier 2 testing under the Clean Air Act (Title V Subpart WWW 60.754). Isotropic identification of landfill methane can be accomplished to identify one source of methane from another. In this case, isotopes of carbon and hydrogen in the methane are analyzed to determine the methane source. 16 NC Division of Waste Management - Solid Waste Section Landfill Gas Monitoring Data Form Notice: This form and any information attached to it are "Public Records" as defined in NC General Statute 132-1. As such, these documents are available for inspection and examination by any person upon request (NC General Statute 132-6). Facility Name: ______________________________________________ Permit Number: ____________________________ Date of Sampling: ___________________ NC Landfill Rule (.0500 or .1600): _____________________________________ Name and Position of Sample Collector: _________________________________________ Type and Serial Number of Gas Meter: _______________________________ Calibration Date of Gas Meter: ___________ Date and Time of Field Calibration: _____________________ Type of Field Calibration Gas (15/15 or 35/50): ____________ Expiration Date of Field Calibration Gas Canister: ________ Pump Rate of Gas Meter: _____________ Ambient Air Temperature: __________ Barometric Pressure: ______________ General Weather Conditions: _____________ Instructions: Under “Location or LFG Well” identify the monitoring wells or describe the location for other tests (e.g., inside buildings). A drawing showing the location of test must be attached. Report methane readings in both % LEL and % methane by volume. A reading in percent methane by volume can be converted to % LEL as follows: % methane by volume = % LEL/20 If your facility has more gas monitoring locations than there is room on this form, please attach additional sheets listing the same information as contained on this form. Certification To the best of my knowledge, the information reported and statements made on this data submittal and attachments are true and correct. I am aware that there are significant penalties for making any false statement, representation, or certification including the possibility of a fine and imprisonment. _________________________________________ _________________________________________ SIGNATURE TITLE 17 SECTION 7 - References Agency for Toxic Substances & Disease Registry. “Landfill Gas Primer- An Overview for Environmental Health Professionals. 2001.” http://www.atsdr.cdc.gov/HAC/landfill/html/toc.html (accessed February 24. 2010). California Environmental Protection Agency. “Landfill Gas Monitoring Well Functionality at 20 California Landfills, 2008”. http://www.calrecycle.ca.gov/Publications/Organics/2008022.pdf (accessed February 24 2010). Florida Department of Environmental Protection. Gas Management Systems, under Rule 62-701.530. http://www.dep.state.fl.us/waste/quick_topics/rules/default.htm (accessed February 24, 2010). Missouri Department of Natural Resources, Flood Grant Team. “An Analysis of Landfill Gas Monitoring Well Design and Construction, 2007”. http://www.clu- in.org/conf/itrc/directpush/prez/Missouri_Study.pdf (accessed February 24, 2010). Missouri Department of Natural Resources. “Design and Construction of Landfill Gas Monitoring Wells”. http://www.dnr.missouri.gov/pubs/pub2054.pdf (accessed February 24. 2010). Wisconsin Department of Natural Resources. Environmental Monitoring for Landfills, under Chapter NR 507.22. http://www.dnr.state.wi.us/org/aw/wm/information/wiacsss.htm (accessed February 24, 2010). “Landfill Gas-an Overview” Landfill-gas.com. Web, 22, Feb. 2010 http://www.landfill-gas.com/webpage -LFG-overview.doc 18 SECTION 8 – Suggested Outline for a Landfill Gas Monitoring Plan 1. Introduction 1.1. Background (project overview, site observations, NCDENR rules referenced) 1.2. Site Geology with discussion of groundwater depth and flow (potentiometric surface map) 1.3. Regulatory Limits 2. Landfill Gas Monitoring 2.1. Landfill Gas Monitoring Well Locations (discussion of reasoning behind proposed locations, discussion of well construction, reference map showing proposed locations, reference table displaying well ID, well depth, screen interval and depth to groundwater) 2.2. Structure and Ambient Sampling 2.3. Landfill Gas Monitoring Frequency 3. Landfill Gas Sampling Procedures 3.1. Detection Equipment Used (discussion of calibration procedures) 3.2. Landfill Gas Sampling Procedure 4. Record Keeping and Reporting 4.1. Landfill Gas Monitoring Data Form 4.2. Sampling Reports 4.3. Permanent Record Keeping 5. Contingency Plan 6. Certification of Professional Geologist 7. Certification of Registered Land Surveyor Figures Map displaying proposed landfill gas monitoring well locations Potentiometric Surface Map Diagram showing construction of stopcock valve or quick connect coupling on well cap Diagram showing well construction of each landfill gas monitoring well Table Table displaying well ID, well depth, screen interval, depth to groundwater Example of landfill gas monitoring data form 19 SECTION 9 – Checklist of Items to be Included in a Landfill Gas Monitoring Plan 1. Depth to groundwater discussion 2. Well locations a. Number of wells b. Well spacing 3. Instrumentation being used a. Calibration procedures 4. Sampling procedures as per the manufacture’s instructions 5. Map of well locations 6. Table describing each well location a. Well ID b. Well depth c. Screen interval d. Depth to groundwater e. Subsurface lithology 7. Diagram of cap construction w/ stopcock valve or quick connect coupling 8. Diagram of well construction 9. Potentiometric surface map 10. Professional Geologist certification 11. Registered Land Surveyor certification Appendix B Landfill Gas Monitoring Data Form (Intended to be most recent version) NC Division of Waste Management – Solid Waste Section Landfill Gas Monitoring Data Form Facility Name:Alexander Co. Landfill Permit Number:02-01 Date of Sampling:NC Landfill Rule (.0500 or .1600):0.1600 Name & Position of Sample Collector: Type & Serial Number of Gas Meter:Calibration Date of Gas Meter: Date & Time of Field Calibration: Type of Field Calibration Gas (15/15 or 35/50):Expiration Date of Field Calibration Gas Canister: Pump Rate of Gas Meter: Ambient Air Temperature: Barometric Pressure:General Weather Conditions: Location or LFG Well ID Sample Tube Purge Time Reading Taken Time Pumped in Seconds Initial CH4 LEL (%) Stabilized CH4 LEL (%) CH4 by Volume (%) O2 (%/Vol) CO2 (%/Vol) H2S (%/Vol)Notes OFFICE 1 SCALEHOUSE TS TS OFFICE SHOP MP-A MP-B MP-C MP-D MP-1 Methane Standard at property line 100% LEL, 5% By Volume, 50,000 PPM Methane Standard in Buildings 25% LEL, 1.25% By Volume, 12,500 PPM of Methane H2S Standard at property line 100% LEL, 4% By Volume, 40,000 PPM H2S Standard in Buildings 25% LEL, 1% By Volume, 10,000 PPM Certification To the best of my knowledge, the information reported and statements made on this data submittal and Attachments are true and correct. I am aware that there are significant penalties for making any false statement, representation, or certification including the possibility of a fine and imprisonment. SIGNATURE TITLE Notice:This form and any information attached to it are “Public Records” as defined in NC General Statute 132-1. As such, these documents are available for inspection and examination by any person upon request (NC General Statute 132-6). Instructions: Under “Location or LFG Well” identify the monitoring wells or describe the location for other tests (e.g., inside buildings). A drawing showing the location of test must be attached. Report CH4 readings in both %LEL and % methane by vol Appendix C LFG Probe Completion Logs