SIGNIFICANT ACCOUNTING POLICIES

The accompanying consolidated financial statements of the Company reflect the application of certain significant accounting policies as described below:

Principles of Consolidation

The accompanying consolidated statements include the accounts of Clean Harbors, Inc. and its majority-owned subsidiaries. All intercompany accounts and transactions have been eliminated in consolidation.

Use of Estimates

The preparation of consolidated financial statements in conformity with accounting principles generally accepted in the United States of America requires management to make estimates and assumptions, which are evaluated on an ongoing basis, that affect the amounts reported in the Company's consolidated financial statements and accompanying notes. Management bases its estimates on historical experience and on various other assumptions it believes to be reasonable at the time under the circumstances, the results of which form the basis for making judgments about the carrying values of assets and liabilities and disclosure, if any, of contingent assets and liabilities and reported amounts of revenues and expenses. Actual results could differ from those estimates and judgments.

Reclassifications

As a result of the adoption of new accounting pronouncements issued in 2015 and discussed further in Note 2 under the heading Recent Accounting Pronouncements, certain balance sheets amounts previously reported in prior period financial statements have been reclassified in accordance with the implemented standards.

Fair Value Valuation Hierarchy

The Company defines fair value as the price that would be received to sell an asset or be paid to transfer a liability in an orderly transaction between market participants at the measurement date. The Company applies the following fair value hierarchy, which prioritizes the inputs used to measure fair value into three levels and bases the categorization within the hierarchy upon the lowest level of input that is available and significant to the fair value measurement. Level 1 inputs are quoted prices in active markets for identical assets or liabilities that the reporting entity has the ability to access at the measurement date. Level 2 utilizes quoted market prices in markets that are not active, broker or dealer quotations, or alternative pricing sources with reasonable levels of price transparency. Level 3 inputs are unobservable inputs for the asset or liability in which there is little, if any, market activity for the asset or liability at the measurement date.

The Company's financial instruments consist of cash and cash equivalents, accounts and unbilled receivable, accounts payable and accrued liabilities and long-term debt obligations. Due to the short-term nature of these instruments, with the exception of long-term debt obligations, their estimated fair value approximates carrying value. Senior unsecured notes are recorded at par.

Cash, Cash Equivalents and Uncashed Checks

Cash and cash equivalents consist primarily of cash on deposit, money market accounts or short-term investments with original maturities of three months or less. The fair value of our cash equivalents is considered a Level 1 measure according to the fair value hierarchy and is adjusted to fair value based on quoted market prices. The Company's cash management program with its revolving credit lender allows for the maintenance of a zero balance in the U.S. bank disbursement accounts that are used to issue vendor and payroll checks. The program can result in checks outstanding in excess of bank balances in the disbursement accounts. When checks are presented to the bank for payment, cash deposits in amounts sufficient to fund the

(2) SIGNIFICANT ACCOUNTING POLICIES (Continued)

checks are made, at the Company's discretion, either from funds provided by other accounts or under the terms of the Company's revolving credit facility. Therefore, until checks are presented for payment, there is no right of offset by the bank and the Company continues to have control over cash relating to both released as well as unreleased checks. Checks that have been written to vendors or employees but have not yet been presented for payment at the Company's bank are classified as uncashed checks as part of accounts payable and added back to cash balances.

Marketable Securities

The Company has classified its marketable securities as available-for-sale and, accordingly, carries such securities at fair value. Unrealized gains and losses are reported, net of tax, as a component of other comprehensive income.

Allowances for Doubtful Accounts

On a regular basis, the Company evaluates its accounts receivable and establishes the allowance for doubtful accounts based on an evaluation of historical collection trends, customer concentration, customer credit ratings, current economic trends and changes in customer payment patterns. Past-due receivable balances are written-off when the Company's internal collection efforts have been deemed unsuccessful in collecting the outstanding balance due.

Credit Concentration

Concentration of credit risks in accounts receivable is limited due to the large number of customers comprising the Company's customer base throughout North America. The Company maintains policies over credit extension that include credit evaluations, credit limits and collection monitoring procedures on a customer-by-customer basis. However, the Company generally does not require collateral before services are performed. As of December 31, 2015 and 2014, no individual customer accounted for more than 10% of accounts receivable. During each of the years ended December 31, 2015, 2014 and 2013, no individual customer accounted for more than 10% of total revenues.

Unbilled Receivables

The Company recognizes unbilled accounts receivable for service and disposal transactions rendered but not invoiced to the customer by the end of the period.

Deferred Costs Relating to Deferred Revenue

Commissions and other incremental direct costs, primarily costs of materials, relating to deferred revenue from the Company’s parts cleaning services, containerized waste services and vacuum services are capitalized and deferred. The deferred costs are included in current assets in the consolidated balance sheet and charged to expense when the related revenues are recognized.

Inventories and Supplies

Inventories are stated at the lower of cost or market. The cost of oil and oil products is principally determined on a first-in, first-out ("FIFO") basis. The cost of supplies and drums, solvent and solution and other inventories is determined on a FIFO or a weighted average cost basis. Costs for oil and oil products, solvent and repair parts include purchase costs, fleet and fuel costs, direct labor, transportation costs and production related costs. The Company continually reviews its inventories for obsolete or unsalable items and adjusts its carrying value to reflect estimated realizable values.

Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consist primarily of prepayments for various services, refundable deposits, and income taxes receivable.

Property, Plant and Equipment (excluding landfill assets)

Property, plant and equipment are stated at cost and include amounts capitalized under capital lease obligations. Expenditures for major renewals and improvements which extend the life or usefulness of the asset are capitalized. Items of an ordinary repair or maintenance nature are charged directly to operating expense as incurred. During the construction and development period of an asset, the costs incurred, including applicable interest costs, are classified as construction-in-progress.

(2) SIGNIFICANT ACCOUNTING POLICIES (Continued)

The Company depreciates and amortizes the cost of these assets, using the straight-line method as follows:



Asset Classification		Estimated Useful Life
Buildings and building improvements
Buildings		30–40 years
Leasehold and building improvements		2–40 years
Camp equipment		8–15 years
Vehicles		3–12 years
Equipment
Capitalized software and computer equipment		3–5 years
Solar equipment		20 years
Containers and railcars		15–20 years
All other equipment		8–20 years
Furniture and fixtures		5–8 years

Leasehold and building improvements have a weighted average life of 10.2 years.

Camp equipment consists of industrial lodging facilities that are utilized to provide lodging services to downstream oil and gas companies in Western Canada.

Solar equipment consists of a solar array that is used to provide electric power for a continuously operating groundwater decontamination pump and treatment system at a closed and capped landfill located in New Jersey.

The Company recognizes an impairment in the carrying value of long-lived assets when the expected future undiscounted cash flows derived from the assets, or group of assets, are less than their carrying value. For the years ended December 31, 2015, 2014 and 2013, the Company did not record impairment charges related to long-lived assets. The Company will continue to assess all of its long-lived assets for impairment as necessary.

Goodwill

Goodwill is comprised of the purchase price of business acquisitions in excess of the fair value assigned at acquisition to the net tangible and identifiable intangible assets acquired. Goodwill is not amortized but is reviewed for impairment annually as of December 31, or when events or changes in the business environment indicate that the carrying value of the reporting unit may exceed its fair value, by comparing the fair value of each reporting unit to its carrying value, including goodwill. If the fair value is less than the carrying amount, a Step II goodwill impairment test is performed to determine if goodwill is impaired. The loss, if any, is measured as the excess of the carrying value of the goodwill over the implied value of the goodwill. See Note 6, "Goodwill and Other Intangible Assets," for additional information related to the Company's goodwill impairment tests and the goodwill impairment charges recorded in 2015 and 2014.

Permits and other intangibles

Permits and intangible assets, such as legal fees, site surveys, engineering costs and other expenditures are recorded as cost. Other intangible assets consist primarily of customer and supplier relationships, trademarks and trade names, and non-compete agreements. Permits relating to landfills are amortized on a units-of-consumption basis. All other permits are amortized over periods ranging from 5 to 30 years on a straight-line basis. Other intangible assets are amortized on a straight-line basis over their respective useful lives, which range from 2 to 20 years.

Finite-lived intangible assets are reviewed for impairment whenever events or changes in circumstances indicate that their carrying value may not be entirely recoverable. When such factors and circumstances exist, management compares the projected undiscounted future cash flows associated with the related asset or group of assets over their estimated useful lives against their respective carrying amounts. The impairment loss, if any, is measured as the excess of the carrying amount over the fair value of the asset or group of assets.

(2) SIGNIFICANT ACCOUNTING POLICIES (Continued)

Indefinite-lived intangible assets are not amortized but are reviewed for impairment annually as of December 31, or when events or changes in the business environment indicate that the carrying value may be impaired. If the fair value of the asset is less than the carrying amount, the Company performs a quantitative test to determine the fair value. The impairment loss, if any,

is measured as the excess of the carrying value of the asset over its fair value. The fair value of the indefinite-lived intangible assets exceeded their carrying values at December 31, 2015 and 2014.

Leases

The Company leases rolling stock, rail cars, equipment, real estate and office equipment under operating leases. Certain real estate leases contain rent holidays and rent escalation clauses. Most of the Company's real estate lease agreements include renewal periods at the Company's option. For its operating leases, the Company recognizes rent holiday periods and scheduled rent increases on a straight-line basis over the lease term beginning with the date the Company takes possession of the leased assets.

Landfill Accounting

The Company amortizes landfill improvements, and certain landfill-related permits over their estimated useful lives. The units-of-consumption method is used to amortize land, landfill cell construction, asset retirement costs and remaining landfill cells and sites. The Company also utilizes the units-of-consumption method to record closure and post-closure obligations for landfill cells and sites. Under the units-of-consumption method, the Company includes future estimated construction and asset retirement costs, as well as costs incurred to date, in the amortization base of the landfill assets. Additionally, where appropriate, as described below, the Company includes probable expansion airspace that has yet to be permitted in the calculation of the total remaining useful life of the landfill. If it is determined that expansion capacity should no longer be considered in calculating the recoverability of a landfill asset, the Company may be required to recognize an asset impairment or incur significantly higher amortization expense. If at any time the Company makes the decision to abandon the expansion effort, the capitalized costs related to the expansion effort are expensed immediately.

Landfill assets—Landfill assets include the costs of landfill site acquisition, permits and cell construction incurred to date. These amounts are recorded at cost, which includes capitalized interest as applicable. Landfill assets, net of amortization, are combined with management's estimate of the costs required to complete construction of the landfill to determine the amount to be amortized over the remaining estimated useful economic life of a site. Amortization of landfill assets is recorded on a units-of-consumption basis, such that the landfill assets should be completely amortized at the date the landfill ceases accepting waste. Amortization totaled $11.2 million, $14.1 million and $16.8 million for the years ended December 31, 2015, 2014 and 2013, respectively. Changes in estimated costs to complete construction are applied prospectively to the amortization rate.

Landfill capacity—Landfill capacity, which is the basis for the amortization of landfill assets and for the accrual of final closure and post-closure obligations, represents total permitted airspace plus unpermitted airspace that management believes is probable of ultimately being permitted based on established criteria. The Company applies the following criteria for evaluating the probability of obtaining a permit for future expansion airspace at existing sites, which provides management a basis to evaluate the likelihood of success of unpermitted expansions:


•	Personnel are actively working to obtain the permit or permit modifications (land use, state, provincial and federal) necessary for expansion of an existing landfill, and progress is being made on the project.


•	Management expects to submit the application within the next year and to receive all necessary approvals to accept waste within the next 5 years.


•	At the time the expansion is included in the Company's estimate of the landfill's useful economic life, it is probable that the required approvals will be received within the normal application and processing time periods for approvals in the jurisdiction in which the landfill is located.


•	The Company or other owner of the landfill has a legal right to use or obtain the right to use the land associated with the expansion plan.


•	There are no significant known political, technical, legal or business restrictions or issues that could impair the success of such expansion.

(2) SIGNIFICANT ACCOUNTING POLICIES (Continued)


•	A financial feasibility analysis has been completed and the results demonstrate that the expansion will have a positive financial and operational impact such that management is committed to pursuing the expansion.


•	Additional airspace and related additional costs, including permitting, final closure and post-closure costs, have been estimated based on the conceptual design of the proposed expansion.

As of December 31, 2015, there was one unpermitted expansion at one location included in the Company's landfill accounting model, which represented 3.0% of the Company's remaining airspace at that date. If actual expansion airspace is significantly different from the Company's estimate of expansion airspace, the amortization rates used for the units-of-consumption method would change, therefore impacting the Company's profitability. If the Company determines that there is less actual expansion airspace at a landfill, this would increase amortization expense recorded and decrease profitability, while if the Company determines a landfill has more actual expansion airspace, amortization expense would decrease and profitability would increase.

As of December 31, 2015, the Company had 11 active landfill sites (including the Company's two non-commercial landfills), which have estimated remaining lives (based on anticipated waste volumes and remaining highly probable airspace) as follows:



		Remaining Lives (Years)	Remaining Highly Probable Airspace (cubic yards) (in thousands)
Facility Name	Location	Remaining Lives (Years)	Permitted	Unpermitted	Total
Altair	Texas	6	686	—	686
Buttonwillow	California	20	7,023	—	7,023
Deer Park	Texas	7	268	—	268
Deer Trail	Colorado	28	1,932	—	1,932
Grassy Mountain	Utah	20	1,839	—	1,839
Kimball	Nebraska	9	243	—	243
Lambton	Ontario	37	5,062	—	5,062
Lone Mountain	Oklahoma	32	4,809	—	4,809
Ryley	Alberta	9	608	880	1,488
Sawyer	North Dakota	45	3,704	—	3,704
Westmorland	California	64	2,732	—	2,732
			28,906	880	29,786

At December 31, 2015 and 2014, the Company had no cubic yards of permitted, but not highly probable, airspace.

The following table presents the remaining highly probable airspace from January 1, 2013 through December 31, 2015 (in thousands of cubic yards):



	2015		2014		2013
Remaining capacity at January 1,	30,544		29,323		29,643
Addition of highly probable airspace, net	516		2,809		1,218
Consumed	(1,274	)	(1,588	)	(1,538	)
Remaining capacity at December 31,	29,786		30,544		29,323

Amortization of cell construction costs and accrual of cell closure obligations—Landfills are typically comprised of a number of cells, which are constructed within a defined acreage (or footprint). The cells are typically discrete units, which require both separate construction and separate capping and closure procedures. Cell construction costs are the costs required to excavate and construct the landfill cell. These costs are typically amortized on a units-of-consumption basis, such that they are completely amortized when the specific cell ceases accepting waste. In some instances, the Company has landfills that are engineered and constructed as "progressive trenches." In progressive trench landfills, a number of contiguous cells form a progressive trench. In those instances, the Company amortizes cell construction costs over the airspace within the entire trench, such that the cell construction costs will be fully amortized at the end of the trench useful life.

(2) SIGNIFICANT ACCOUNTING POLICIES (Continued)

The design and construction of a landfill does not create a landfill asset retirement obligation. Rather, the asset retirement obligation for cell closure (the cost associated with capping each cell) is incurred in relatively small increments as waste is placed in the landfill. Therefore, the cost required to construct the cell cap is capitalized as an asset retirement cost and a liability of an equal amount is established, based on the discounted cash flow associated with each capping event, as airspace is consumed. Spending for cell capping is reflected as environmental expenditures within operating activities in the statement of cash flows.

Landfill final closure and post-closure liabilities—The balance of landfill final closure and post-closure liabilities at December 31, 2015 and 2014 was $32.0 million and $29.9 million, respectively. The Company has material financial commitments for the costs associated with requirements of the Environmental Protection Agency ("EPA") and the comparable regulatory agency in Canada for landfill final closure and post-closure activities. In the United States, the landfill final closure and post-closure requirements are established under the standards of the EPA, and are implemented and applied on a state-by-state basis. The Company develops estimates for the cost of these activities based on an evaluation of site-specific facts and circumstances, including the Company's interpretation of current regulatory requirements and proposed regulatory changes. Such estimates may change in the future due to various circumstances including, but not limited to, permit modifications, changes in legislation or regulations, technological changes and results of environmental studies.

Final closure costs are the costs incurred after the site ceases to accept waste, but before the landfill is certified as closed by the applicable state regulatory agency. These costs generally include the costs required to cap the final cell of the landfill (if not included in cell closure), the costs required to dismantle certain structures for landfills and other landfill improvements, and regulation-mandated groundwater monitoring, and leachate management. Post-closure costs involve the maintenance and monitoring of a landfill site that has been certified closed by the applicable regulatory agency. These costs generally include groundwater monitoring and leachate management. Regulatory post-closure periods are generally 30 years after landfill closure. Final closure and post-closure obligations are accrued on a units-of-consumption basis, such that the present value of the final closure and post-closure obligations are fully accrued at the date the landfill discontinues accepting waste.

Cell closure, final closure and post closure costs (also referred to as "asset retirement obligations") are calculated by estimating the total obligation in current dollars, adjusted for inflation (1.02% during 2015 and 2014) and discounted at the Company's credit-adjusted risk-free interest rate (5.99% and 6.54% during 2015 and 2014, respectively.)

Non-Landfill Closure and Post-Closure Liabilities

Non-landfill closure costs include costs required to dismantle and decontaminate certain structures and other costs incurred during the closure process. Post-closure costs, if required, include associated maintenance and monitoring costs as required by the closure permit. Post-closure periods are performance-based and are not generally specified in terms of years in the closure permit, but generally range from 10 to 30 years or more.

The Company records its non-landfill closure and post-closure liability by: (i) estimating the current cost of closing a non-landfill facility and the post-closure care of that facility, if required, based upon the closure plan that the Company is required to follow under its operating permit, or in the event the facility operates with a permit that does not contain a closure plan, based upon legally enforceable closure commitments made by the Company to various governmental agencies; (ii) using probability scenarios as to when in the future operations may cease; (iii) inflating the current cost of closing the non-landfill facility on a probability weighted basis using the inflation rate to the time of closing under each probability scenario; and (iv) discounting the future value of each closing scenario back to the present using the credit-adjusted risk-free interest rate. Non-landfill closure and post-closure obligations arise when the Company commences operations.

The balance of non-landfill closure and post-closure liabilities at December 31, 2015 and 2014 was $24.2 million and $20.8 million, respectively. Management bases estimates for non-landfill closure and post-closure liabilities on its interpretation of existing permit and regulatory requirements for closure and post-closure maintenance and monitoring. The Company's cost estimates are calculated using internal sources as well as input from third party experts. Management uses probability scenarios to estimate when future operations will cease and inflates the current cost of closing the non-landfill facility on a probability weighted basis using the appropriate inflation rate and then discounting the future value to arrive at an estimated present value of closure and post-closure costs. The estimates for non-landfill closure and post-closure liabilities are inherently uncertain due to the possibility that permit and regulatory requirements will change in the future, impacting the estimation of total costs and the timing of the expenditures. Management reviews non-landfill closure and post-closure liabilities for changes to key assumptions that would impact the amount of the recorded liabilities. Changes that would prompt management to revise a liability estimate include changes in legal requirements that impact the Company's expected closure plan or scope of work, in

(2) SIGNIFICANT ACCOUNTING POLICIES (Continued)

the market price of a significant cost item, in the probability scenarios as to when future operations at a location might cease, or in the expected timing of the cost expenditures. Changes in estimates for non-landfill closure and post-closure events immediately impact the required liability and the value of the corresponding asset. If a change is made to a fully-consumed asset, the adjustment is charged immediately to expense. When a change in estimate relates to an asset that has not been fully consumed, the adjustment to the asset is recognized in income prospectively as a component of amortization. Historically, material changes to non-landfill closure and post-closure estimates have been infrequent.

Remedial Liabilities

The balance of remedial liabilities at December 31, 2015 and 2014 was $132.0 million and $155.1 million, respectively. Remedial liabilities, including Superfund liabilities, include the costs of removal or containment of contaminated material, treatment of potentially contaminated groundwater and maintenance and monitoring costs necessary to comply with regulatory requirements. Most of the Company's remedial liabilities relate to the active and inactive hazardous waste treatment and disposal facilities which the Company acquired in the last 14 years and 35 Superfund sites owned by third parties for which the Company agreed to indemnify certain remedial liabilities owed or potentially owed to governmental entities by the sellers of certain assets (the "CSD assets") which the Company acquired in 2002. The Company performed extensive due diligence to estimate accurately the aggregate liability for remedial liabilities to which the Company became potentially liable as a result of the acquisitions. The Company's estimate of remedial liabilities involved an analysis of such factors as: (i) the nature and extent of environmental contamination (if any); (ii) the terms of applicable permits and agreements with regulatory authorities as to cleanup procedures and whether modifications to such permits and agreements will likely need to be negotiated; (iii) the cost of performing anticipated cleanup activities based upon current technology; and (iv) in the case of Superfund and other sites where other parties will also be responsible for a portion of the cleanup costs, the likely allocation of such costs and the ability of such other parties to pay their share. Remedial liabilities and on-going operations are reviewed quarterly and adjustments are made as necessary.

The Company periodically evaluates potential remedial liabilities at sites that it owns or operates or to which the Company or the sellers of the CSD assets (or the respective predecessors of the Company or such sellers) transported or disposed of waste, including 128 Superfund sites as of December 31, 2015. The Company periodically reviews and evaluates sites requiring remediation, including Superfund sites, giving consideration to the nature (i.e., owner, operator, arranger, transporter or generator) and the extent (i.e., amount and nature of waste hauled to the location, number of years of site operations or other relevant factors) of the Company's (or such sellers') alleged connection with the site, the extent (if any) to which the Company believes it may have an obligation to indemnify cleanup costs in connection with the site, the regulatory context surrounding the site, the accuracy and strength of evidence connecting the Company (or such sellers) to the location, the number, connection and financial ability of other named and unnamed potentially responsible parties ("PRPs") and the nature and estimated cost of the likely remedy. Where the Company concludes that it is probable that a liability has been incurred and an amount can be estimated, a provision is made, based upon management's judgment and prior experience, of such estimated liability.

Remedial liabilities are inherently difficult to estimate. Estimating remedial liabilities requires that the existing environmental contamination be understood. There are risks that the actual quantities of contaminants differ from the results of the site investigation, and that contaminants exist that have not been identified by the site investigation. In addition, the amount of remedial liabilities recorded is dependent on the remedial method selected. There is a risk that funds will be expended on a remedial solution that is not successful, which could result in the additional incremental costs of an alternative solution. Such estimates, which are subject to change, are subsequently revised if and when additional or new information becomes available.

Remedial liabilities are discounted only when the timing of the payments is estimable and the amounts are determinable. Management's experience has been that the timing of payments for remedial liabilities is not usually estimable, and therefore the amounts of remedial liabilities are not generally discounted. In the case of remedial liabilities assumed in connection with acquisitions, acquired liabilities are recorded under purchase accounting at fair value. Accordingly, as of the respective acquisition dates, the Company recorded the remedial liabilities assumed as part of acquisitions at their fair value, which were calculated by inflating costs in current dollars using an estimate of future inflation rates as of the respective acquisition dates until the expected time of payment, and then discounting the amount of the payments to their present value using a risk-free discount rate as of the acquisition dates. Discounts were and will be applied to the environmental liabilities as follows:

(2) SIGNIFICANT ACCOUNTING POLICIES (Continued)


•	Remedial liabilities assumed relating to acquisitions are and will continue to be inflated using the inflation rates at the time of each acquisition (ranging from 1.01% to 2.57%) until the expected time of payment, then discounted at the risk-free interest rate at the time of such acquisition (ranging from 2.88% to 5.99%).


•	Remedial liabilities incurred subsequent to the acquisitions and remedial liabilities of the Company that existed prior to the acquisitions have been and will continue to be recorded at the estimated current value of the liabilities, which is usually neither increased for inflation nor reduced for discounting.

Foreign Currency

During the year ended December 31, 2015 and 2014, the Company had operations in Canada, and to a much lesser extent, Mexico and Trinidad. Assets and liabilities are translated to U.S. dollars at the exchange rate in effect at the balance sheet date and revenue and expenses at the average exchange rate for the period. Gains and losses from the translation of the consolidated financial statements of foreign subsidiaries into U.S. dollars are included in stockholders' equity as a component of accumulated other comprehensive income. Gains and losses resulting from foreign currency transactions are recognized in the consolidated statements of income. Recorded balances that are denominated in a currency other than the functional currency are remeasured to the functional currency using the exchange rate at the balance sheet date and gains or losses are recorded in the statements of income.

Revenue Recognition and Deferred Revenue

During 2015, the Company provided environmental, energy, lodging and industrial services through six segments: Technical Services, Industrial and Field Services, Kleen Performance Products, SK Environmental Services, Lodging Services, and Oil and Gas Field Services. The Company recognizes revenue when persuasive evidence of an arrangement exists, delivery has occurred or services have been rendered, the price is fixed or determinable, and collection is reasonably assured. Revenue is recognized net of estimated allowances. Revenue is generated by short-term projects, most of which are governed by master service agreements that are long-term in nature. The master service agreements are typically entered into with the Company's larger customers and outline the pricing and legal frameworks for such arrangements.

Due to the nature of the Company's business and the invoices that result from the services provided, customers may withhold payments and attempt to renegotiate amounts invoiced. Accordingly, management establishes a revenue allowance to cover the estimated amounts of revenue that may need to be credited to customers' accounts in future periods. The Company records a provision for revenue allowances based on specific review of particular customers, historical trends and other relevant information.

Technical Services revenue is generated from fees charged for hazardous material management and disposal services including onsite environmental management services, collection and transportation, packaging, recycling, treatment and disposal of hazardous and non-hazardous waste. Services are provided based on purchase orders or agreements with the customer and include prices based upon units of volume of waste, and transportation and other fees. Collection and transportation, and packaging revenues are recognized when the transported waste is received at the disposal facility. Revenues for treatment and disposal of hazardous waste are recognized upon completion of wastewater treatment, final disposition in a landfill or incineration of the waste, all at Company-owned sites, or when the waste is shipped to a third party for processing and disposal. Revenues from recycled oil and recycled catalyst are recognized upon shipment to the customer. Revenue for all other Technical Services is recognized when services are rendered. The Company, at the request of a customer, periodically enters into bundled arrangements for the collection and transportation and disposal of waste. The Company accounts for such arrangements as multiple-element arrangements with separate units of accounting. The Company measures and allocates the consideration from the arrangement to the separate units, based on evidence of the estimated selling price for each deliverable. Revenues from waste that is not yet completely processed and disposed and the related costs are deferred. The revenue is recognized and the deferred costs are expensed when the related services are completed.

Industrial Services provides industrial and specialty services, such as high-pressure and chemical cleaning, catalyst handling, decoking and pigging to refineries, chemical plants, oil sands facilities, pulp and paper mills, and other industrial facilities. These services are provided based on purchase orders or agreements with the customer and include prices based upon daily, hourly or job rates for equipment, materials and personnel. Revenues are recognized over the term of the agreements or as services are performed. Field Services provides cleanup services on customer sites or other locations on a scheduled or

(2) SIGNIFICANT ACCOUNTING POLICIES (Continued)

emergency response basis. The Company's services are provided based on purchase orders or agreements with the customer and include prices based upon daily, hourly or job rates for equipment, materials and personnel. Revenues are recorded as services are performed. Revenue is recognized on contracts with retainage when services have been rendered and collectability is reasonably assured.

Kleen Performance Products revenue is generated from re-refining used oil to produce high quality base and blended lubricating oils, and recycling used oil collected in excess of the Company's re-refining capacity into recycled fuel oil. The high quality base and blended lubricating oils are sold to third-party distributors, retailers, government agencies, fleets, railroads and industrial customers. The recycled fuel oil is sold to asphalt plants, industrial plants, blenders, pulp and paper companies, vacuum gas oil producers and marine diesel oil producers. Revenue is recognized upon the transfer of title.

SK Environmental Services revenue is generated from providing parts cleaning services, containerized waste services, oil collection services and other complementary products and services. Revenue is recognized when products are delivered and services are performed. Parts cleaning services generally consist of placing a specially designed parts washer at a customer's premises and then, on a recurring basis, delivering clean solvent or aqueous-based washing fluid, cleaning and servicing the parts washer and removing the used solvent or aqueous fluid. The Company also services customer-owned parts washers. Revenue from parts cleaning services is recognized over the service interval. Service intervals represent the actual amount of time between service visits to a particular parts cleaning customer. Average service intervals vary from seven to 14 weeks depending on several factors, such as customer accommodation, types of machines serviced and frequency of use. Containerized waste services consist of profiling, collecting, transporting and recycling or disposing of a wide variety of hazardous and non-hazardous wastes. Collection and transportation, and packaging revenues are recognized when the transported waste is received at the disposal facility. Revenues for treatment and disposal of the waste is recognized upon disposal, or when the waste is shipped to a third party for processing and disposal. Other complementary products and services include vacuum services, sale of allied supply products and other environmental services.

Lodging Services provides accommodation services, along with catering and hospitality primarily in remote areas of Western Canada. In addition, within Lodging Services is a manufacturing unit that provides construction of modular buildings including modular camp accommodations and wastewater solutions. Revenue for lodging and related services is recognized in the period each room is used by the customer based on the related lodging agreements. Revenue for manufacturing services is recognized based on contracted terms resulting in either a percentage of completion methodology or upon transfer of ownership of completed units.

Oil and Gas Field Services provides fluid handling, fluid hauling, production servicing, surface rentals, seismic services, and directional boring services to the energy sector serving oil and gas exploration and production and power generation. These services are provided based on purchase orders or agreements with the customer and include prices based upon daily, hourly or job rates for equipment, materials and personnel. Revenues for such services are recognized over the term of the agreements or as services are performed. Oil and Gas Field Services also provides equipment rentals to support drill sites. Revenue from rentals is recognized ratably over the rental period.

For all periods presented, amounts billed to customers related to shipping and handling are classified as revenue and the Company's shipping and handling costs are included in costs of revenues. In the course of the Company's operations, it collects sales tax from its customers and recognizes a current liability which is then relieved when the taxes are remitted to the appropriate governmental authorities. The Company excludes the sales tax collected from its revenues.

Advertising Expense

Advertising costs are expensed as incurred. Advertising expense was approximately $15.0 million in 2015, $11.3 million in 2014 and $10.8 million in 2013.

Stock-Based Compensation

Stock-based compensation cost is measured at the grant date based on the fair value of the award and is recognized as expense over the requisite service period, which generally represents the vesting period, and includes an estimate of awards that will be forfeited. In addition, the Company issues awards with performance targets which are recognized as expense over the requisite service period when management believes it is probable those targets will be achieved. The fair value of the

(2) SIGNIFICANT ACCOUNTING POLICIES (Continued)

Company's grants of restricted stock are based on the quoted market price for the Company's common stock on the respective dates of grant. The fair value of stock options is calculated using the Black-Scholes option-pricing model. Compensation

expense is based on the number of awards expected to vest. Forfeitures estimated when recognizing compensation expense are adjusted when actual forfeitures differ from the estimate.

Income Taxes

There are two major components of income tax expense, current and deferred. Current income tax expense approximates cash to be paid or refunded for taxes for the applicable period. Deferred tax expense or benefit is the result of changes between deferred tax assets and liabilities. Deferred tax assets and liabilities are determined based upon the temporary differences between the financial statement basis and tax basis of assets and liabilities as well as from net operating loss and tax credit carryforwards as measured by the enacted tax rates, which will be in effect when these differences reverse. The Company evaluates the recoverability of future tax deductions and credits and a valuation allowance is established by tax jurisdiction when, based on an evaluation of objective verifiable evidence, it is more likely than not that some portion or all of deferred tax assets will not be realized.

The Company recognizes and measures a tax benefit from uncertain tax positions when it is more likely than not that the tax position will be sustained on examination by the taxing authorities, based on the technical merits of the position. The Company recognizes a liability for unrecognized tax benefits resulting from uncertain tax positions taken or expected to be taken in a tax return. The Company adjusts these liabilities when its judgment changes as a result of the evaluation of new information not previously available. Due to the complexity of some of these uncertainties, the ultimate resolution may result in a payment that is materially different from the current estimate or future recognition of an unrecognized benefit. These differences will be reflected as increases or decreases to income tax expense in the period in which they are determined.

The Company recognizes interest and penalties related to unrecognized tax benefits within the income tax expense line in the consolidated statements of income. Accrued interest and penalties are included within deferred taxes, unrecognized tax benefits and other long-term liabilities line in the consolidated balance sheet.

Earnings (Loss) per Share ("EPS")

Basic EPS is calculated by dividing income available to common stockholders by the weighted average number of common shares outstanding during the period. Diluted EPS gives effect to all potentially dilutive common shares that were outstanding during the period.

Business Combinations

For all business combinations, the Company records 100% of all assets and liabilities of the acquired business, including goodwill, at their estimated fair values. Acquisition-related costs are expensed in the period in which the costs are incurred and the services are received.

Recent Accounting Pronouncements

Standards implemented

In April 2014, the Financial Accounting Standards Board (“FASB”) issued Accounting Standard Update (“ASU”)

2014-08, Presentation of Financial Statements (Topic 205) and Property, Plant, and Equipment (Topic 360). The amendments in ASU 2014-08 provide guidance for the recognition and disclosure of discontinued operations. The adoption of ASU 2014-08 did not have an impact on the Company's consolidated financial statements.

In April 2015, the FASB issued ASU 2015-03, Interest-Imputation of Interest (Subtopic 835-30): Simplifying the Presentation of Debt Issuance Costs (ASU 2015-03). ASU 2015-03 requires that debt issuance costs related to a recognized liability in the balance sheet be presented as a direct deduction to that liability rather than as an asset. Final guidance on this standard, issued as ASU 2015-15 in August 2015, includes an SEC staff announcement that the SEC staff will not object to an entity presenting the cost of securing a revolving line of credit as an asset, regardless of whether a balance is outstanding. The Company elected to early adopt this new standard beginning December 31, 2015 and retrospectively reclassified $14.9 million of debt issuance costs associated with the Company's long-term obligations as of December 31, 2014 from other assets to long-term obligations. This reclassification only affected presentation and therefore did not have an impact on the Company’s results

(2) SIGNIFICANT ACCOUNTING POLICIES (Continued)

of operations. Costs associated with securing the Company’s revolving credit facility remained presented as Deferred financing costs within the Other assets section of the consolidated balance sheets for all periods presented.

In November 2015, FASB issued ASU 2015-17, Income Taxes (Topic 740). The amendment provides guidance to simplify the presentation of deferred taxes by requiring that deferred liabilities and assets be classified as noncurrent in a classified balance sheet. The Company elected to early adopt this new standard beginning December 31, 2015 and prospectively applied ASU 2015-17, therefore deferred tax balances presented for periods prior to December 31, 2015 have not been recast in connection with the implementation of this standard. The adoption of this standard only affects the classification of deferred tax amounts and has no impact on the Company’s results of operations.

Standards to be implemented

In May 2014, FASB issued ASU 2014-09, Revenue from Contracts with Customers (Topic 606). ASU 2014-09 outlines a single comprehensive model for entities to use in accounting for revenue arising from contracts with customers and supersedes most current revenue recognition guidance, including industry-specific guidance. In August 2015, FASB issued ASU 2015-14 which deferred the effective date of ASU 2014-09 for all entities by one year. This new guidance is currently effective for annual reporting periods (including interim reporting periods within those periods) beginning after December 15, 2017.

In February 2015, the FASB issued ASU 2015-02, Consolidation (Topic 810). The amendment provides guidance regarding amendments to the consolidation analysis. The amendments in this update are currently effective for annual reporting periods (including interim reporting periods within those periods) beginning after December 15, 2015.

In January 2016, FASB issued ASU 2016-01, Financial Instruments - Overall (Subtopic 825-10). The amendment provides guidance to enhance the reporting model for financial instruments to provide users of financial statements with more decision-useful information. The amendment in this update is effective for fiscal years beginning after December 15, 2018, and interim periods within fiscal years beginning after December 15, 2019.

The Company is currently evaluating the impact that the above standards to be implemented will have on the Company's consolidated financial statements.

In July 2015, FASB issued ASU 2015-11, Inventory (Topic 330). The amendment provides guidance regarding the measurement of inventory. Entities should measure inventory within the scope of this update at the lower of cost and net realizable value. The amendments in this update are currently effective for annual reporting periods (including interim reporting periods within those periods) beginning after December 15, 2016. Adoption is not expected to have a material impact on the Company's consolidated financial statements.

In September 2015, FASB issued ASU 2015-16, Business Combinations (Topic 805). The amendment provides guidance to simplify the accounting for adjustments made to provisional amounts recognized in a business combination. This amendment eliminates the requirement to retrospectively account for those adjustments. The amendment in this update is currently effective for annual reporting periods (including interim reporting periods within those periods) beginning after December 15, 2015. Adoption is not expected to have a material impact on the Company's consolidated financial statements.