A P I PUBLS452’7 9 3 = 0’732290 05LïLO2 556 = Evaluation of Limiting Constituents Suggested for Land Disposal of Exploration and Production Wastes HEALTH AND ENVIRONMENTAL SCIENCES DE
Limiting Constituents
Salts and hydrocarbons are the main constituents of concern in onshore exploration and production operations, as they can lead to phytotoxicity Sodium salts, in particular, can harm soil structure, disrupt the natural soil-plant-water relationships, and contribute to increased erosion.
(Miller and Honarvar, 1 9 7 5 ; Ferrante, 1 9 8 1 ; Freeman and Deuel,
1 9 8 4 ; Nelson et al., 1 9 8 4 ) Salts and hydrocarbons associated with E&P wastes may pose a significant threat to surface and groundwater resources when not properly managed (Henderson, 1 9 8 2 ;
Salinity
Salinity refers to the concentration of cations and anions in water, with major ions including sodium (Na), calcium (Ca), magnesium (Mg), potassium (K), chloride (Cl), sulfate (SO₄), bicarbonate (HCO₃), carbonate (CO₃), and hydroxide (OH) Electrical conductivity (EC) indicates the total ionic strength of these ions, while sodium adsorption ratio (SAR) and exchangeable sodium percentage (ESP) assess the impact of specific ions under certain conditions.
Electrical conductivity (EC) refers to the ability of charged particles in a solution to conduct electric current, which is influenced mainly by the concentration and type of ionic species present It is measured in reciprocal units of resistance and is commonly reported in mmho/cm Since dissolved solids are primarily composed of salts that dissociate into charged particles, EC serves as an indirect and approximate measure of total dissolved solids (TDS).
Total Dissolved Solids (TDS) refers to the unfilterable residue found in water after evaporation, measured in milligrams per liter (mg/liter) This residue mainly consists of salts, but it can also contain organic materials, such as humic substances or anthropogenic compounds, as well as mineral colloids that pass through filters.
The concentration of a specific salt in pure water directly affects the electrical conductance of the solution, as noted by Barrow (1966) However, this relationship becomes less accurate at high salt concentrations, in solutions containing mixed salt species, or when nonionic dissolved species are present More practical are the empirical correlations observed between total dissolved solids (TDS) and electrical conductivity (EC) in various aqueous solutions.
A P I P U B L r 4 5 2 7 9 3 0732290 0517110 622 with the regression constant “A” (slope), being used as a conver- sion factor Values of ‘A” have been found to range naturally from
The total dissolved solids (TDS) in saline/sodic soils can be estimated using a constant value of 640 cm.mg/mmho.liter, as noted by the U.S Salinity Laboratory Staff in 1954 For instance, with an electrical conductivity (EC) of 4 mmho/cm, this results in a TDS of 2560 mg/liter However, a recent analytical review by the EPA in 1987, along with a parallel review by the API, suggests that a more accurate "A" value of 613 should be used for estimating TDS in these contexts.
E&P wastes when calculated from E C This value is used in subse- quent TDS calculations within this document
TDS is often an unreliable indicator of salinity in many exploration and production (E&P) wastes, primarily due to inaccuracies caused by hydrocarbons and fine clay during the filtration process For a more accurate assessment of salinity on a mass basis, it is advisable to estimate it using electrical conductivity (EC).
EC has long been the parameter of choice in defining salinity hazards associated with production agriculture
If one wants the perspec-
While certain elements like boron can be harmful to plants, the primary negative impact of salinity arises from the heightened osmotic pressure in the soil solution that interacts with plant roots.
(Haywood and Wadleigh, 1949; U.S Salinity Laboratory Staff,
1954) Osmosis is a process that controls the movement of water between solutions and depends upon the number of dissolved mole- cules or ions (salinity) Water flows from lower to higher
A P I PUBLa4527 9 3 = 0732290 0 5 l 1 7 L l L 5 6 9 = osmotic p r e s s u r e P l a n t s h a v e a n osmotic p r e s s u r e a s s o c i a t e d w i t h t h e i r c e l l s o l u t i o n which v a r i e s g r e a t l y between p l a n t species a n d t o some degree between c u l t i v a r s w i t h i n species If t h e osmotic p r e s s u r e i n s o i l s o l u t i o n o u t s i d e t h e p l a n t e x c e e d s t h a t i n s i d e , t h e p l a n t s w i l t s The p o i n t of permanent w i l t i n g i s r e a c h e d when t h e p l a n t c a n n o t recover e v e n when e x p o s e d t o less s a l i n e water
S a l t s a l s o a f f e c t p l a n t s by d i s r u p t i n g normal n u t r i e n t u p t a k e and u t i l i z a t i o n ( K r a m e r , 1 9 6 9 ) The mechanism i s one o f s i m p l e a n t a g o n i s m , whereby a g i v e n s a l t specie i n e x c e s s i n h i b i t s t h e p l a n t i n t a k e of r e q u i r e d e l e m e n t s The e f f e c t i s u s u a l l y m a n i f e s t e d a s a d e f i c i e n c y r e s u l t i n g i n lowered y i e l d e x p e c t a t i o n s o r o v e r a l l c r o p q u a l i t y
T h e r e i s n o o n e c r i t i c a l o r t h r e s h o l d s a l i n i t y l e v e l where a l l p l a n t s f a i l t o grow o r m a i n t a i n a c c e p t a b l e y i e l d s (Maas a n d Hoffman, 1 9 7 7 ) G e n e r a l crop r e s p o n s e t o s o i l s a l i n i t y i s shown i n Table 1 (U.S S a l i n i t y L a b o r a t o r y S t a f f , 1 9 5 4 ) The s e n s i t i v i t i e s of v a r i o u s a g r i c u l t u r a l crops t o s a l t a r e shown i n
( 1 9 8 6 ) For example: A t a n EC of 4 mmho/cm, b a r l e y , c o t t o n , a n d bermuda g r a s s a r e n o t a f f e c t e d by s a l t , whereas y i e l d s a r e e x p e c t e d t o decrease f o r r i c e a n d c o r n (0-15%), a l f a l f a a n d s u g a r c a n e (15-30%) a n d b e a n s ( 3 0 - 5 0 % ) Y i e l d r e s p o n s e i n t e r v a l s shown i n F i g u r e s 1 t h r o u g h 3 were d e v e l o p e d from a g r i c u l t u r a l
EC E f f e c t on Crop Y i e l d (mmho/cm)
S l i g h t t o none Many c r o p s a f f e c t e d Only t o l e r a n t c r o p s y i e l d w e l l Only v e r y t o l e r a n t c r o p s y i e l d w e l l s y s t e m s r e c e i v i n g s a l t - c o n t a i n i n g i r r i g a t i o n o v e r t h e l o n g t e r m a n d may o v e r e s t i m a t e t h e a n t i c i p a t e d r e s p o n s e f o r a one-time l a n d d i s p o s a l o f E & P wastes Based on Lunin (19671, t h e a u t h o r s b e l i e v e t h a t s a l i n i t y g u i d e l i n e s f o r c o n t i n u a l u s e s y s t e m s c a n r e a s o n a b l y be d o u b l e d f o r a one-time a p p l i c a t i o n ; t h e r a t i o n a l e b e i n g t h a t s a l t a c c u m u l a t e d o u t s i d e t h e b u l k s o i l mass ( i n p o r e s a n d on p e d s u r f a c e s ) i s more e a s i l y d i s p l a c e d t h a n t h a t p e n e t r a t e d i n t o a n d reacted w i t h t h e b u l k s o i l mass
If t h e s a l i n i t y i s i n i t i a l l y t o o h i g h f o r a g i v e n c r o p a f t e r l a n d a p p l i c a t i o n s o f waste, s o i l s w i l l g e n e r a l l y r e c o v e r f o l l o w i n g r a i n f a l l o r i r r i g a t i o n c o n t a i n i n g l e s s s a l t b e c a u s e e x c e s s s a l t s are l e a c h e d when a d e q u a t e d r a i n a g e i s p r e s e n t Growth o f more s a l t t o l e r a n t p l a n t s may be d e s i r a b l e d u r i n g t h e i n t e r i m
Co cn t cd nn aia a o a @ o
Reclamation of salt-affected soils can be accelerated by applying calcium sulfate (gypsum), which facilitates the exchange of sodium for calcium, enhancing soil recovery (Foth and Turk, 1972; Oster and Rhoades).
Plants cultivated in gypsiferous soils can withstand an electrical conductivity (EC) approximately 2 mmho/cm higher than the values indicated in previous studies (Mass, 1986) This increased tolerance is attributed to the dissolution of gypsum at moisture levels used for saturated soil extract analysis, which differs from the moisture conditions typically found in the field.
USDA Handbook 60 (U.S Salinity Laboratory Staff,1954) clas- sifies water with EC values above 2.25 mmho/cm as unfit f o r agricultural purposes except under very special circumstances
Soils with salinity levels exceeding 4 mmho/cm are classified as saline, which is particularly detrimental for salt-sensitive crops Research by Miller and Pesaran (1980) indicated that high soluble salt concentrations in a 1:1 mud-soil mixture negatively impacted plant growth, with yield decreases of only 7% for green beans and 13% for sweet corn when the electrical conductivity (EC) was below 8 mmho/cm Conversely, Nelson et al (1984) observed average yield reductions of 20% and 38% for Swiss chard and rye-grass, respectively, in conditions where the salinity ranged from 6.3 to 18.6 mmho/cm, exceeding the recommended threshold of 4 mmho/cm Additionally, Tucker (1985) noted that the incorporation of drilling mud resulted in EC values ranging from 1.3 to 5.3 mmho/cm.
The study found that an electrical conductivity (EC) level of 4.5 mmho/cm had no adverse effects on bermudagrass, while a level of 1.7 mmho/cm showed no negative impact on alfalfa Additionally, a significant decrease in EC was observed over time after application, indicating the leaching of salts from the root zone.
A one-time application of EC guidelines at 4 mmho/cm is expected to result in less than a 15% yield decrease for most crops However, in situations where factors such as precipitation, drainage, or specific crop types impose unique waste management restrictions, adjustments to waste addition levels or land use may be necessary during the soil recovery period.
In areas of net infiltration, the soluble salts are trans- ported from the surface to lower soil zones Murphy and Kehew
Research indicates that soluble salts from saturated brine drilling fluids, with an electrical conductivity (EC) exceeding 200 mmho/cm, can threaten localized groundwater resources, significantly surpassing the recommended threshold of 4 mmho/cm Additionally, Bates (1988) found that when a freshwater drilling fluid was mixed with surface soil, chloride ions (C1) were not retained in the zone of incorporation.
The criteria of 4 mmho/cm (2452 mg/liter TDS for riA1r = 613) are unlikely to significantly affect groundwater, even in highly sensitive hydrological environments Water and its dissolved constituents do not travel through soils as a single unit; rather, their movement is influenced by natural redistribution mechanisms, including water potentials, pore dynamics, and dispersion.
API PUBL* 90, when s a l i n i t i e s w e r e < 4 mmho/cm T r e a t m e n t c o n s i s t e d
A P I PUBLm4527 9 3 0732290 0517123 280 of blending waste solids with native soils at chemically defined mix ratios in conjunction with gypsum and fertilizer amendments
The API Environmental Guidance Document advises a Sodium Adsorption Ratio (SAR) of less than 12 and an Exchangeable Sodium Percentage (ESP) of less than 15% for the land disposal of exploration and production (E&P) wastes These thresholds are widely recognized by the USDA as effective measures to prevent soil sodicity, as supported by research from the U.S Salinity Laboratory in 1954 Additionally, both field and laboratory studies involving drilling muds have confirmed these values as appropriate standards.
Guidance values are crucial for determining the final disposition or closure status of waste, specifically regarding the types of waste that can be safely disposed of on land Operators must be ready to implement necessary management strategies for any waste that exceeds these recommended values.
These values do not limit
Hydrocarbons
Crude oil and diesel are the principal hydrocarbons associ- ated with E&P wastes (Miller et al., 1980; Thoresen and Hinds,
1983; Whitfill and Boyd, 1987) They are sometimes added to water base drill systems to lubricate the drill bit and pipe string
4 % (Freeman and Deuel, 1986) Other E&P waste such as tank bottoms, emulsions, and oil-contaminated soil may have higher concentrations of O&G
0&G levels in freshwater drilling wastes are generally <
Crude o i l and d i e s e l f r a c t i o n s a r e comprised of a complex a r r a y of s a t u r a t e and aromatic hydrocarbons (Thoresen and Hinds,
1983, Oudot e t a l , 1 9 8 9 ) Both f r a c t i o n s a r e r e a d i l y p a r t i t i o n e d from water by s o l v e n t u s i n g a s e p a r a t o r y f u n n e l o r e x t r a c t e d from s o l i d m i n e r a l components u s i n g a Soxhlet a p p a r a t u s (Brown e t a 1 , 1 9 8 3 ) and r e p o r t e d c o l l e c t i v e l y a s o i l and g r e a s e ( 0 6 G ) Methylene c h l o r i d e i s t h e s o l v e n t of choice owing t o i t s e f f i c i e n c y f o r e x t r a c t i n g petroleum hydrocarbons without Co-extracting s i g n i f i c a n t q u a n t i t i e s of n a t u r a l l y o c c u r r i n g o r g a n i c m a t t e r (Brown and D e u e l , 1 9 8 3 )
A c o n s i d e r a b l e amount of r e s e a r c h has been c a r r i e d out on t h e d e t r i m e n t a l e f f e c t s of crude o i l and gas on p l a n t s and s o i l s (Baldwin, 1 9 2 2 ; Murphy, 1 9 2 9 ; Schollenberger, 1930; Harper, 1939;
P l i c e , 1948; Schwendinger, 1 9 6 8 ; Garner, 1 9 7 1 ; Odu, 1 9 7 2 ) The most p h y t o t o x i c compounds a r e lower molecular weight aromatic hydrocarbons p r e s e n t i n i t i a l l y o r formed a s m e t a b o l i t e s of t h e v a r i o u s d e g r a d a t i o n p r o c e s s e s (Baker, 1 9 7 0 ; P a t r i c k , 1 9 7 1 )
Udo and Fayemi, 1975) r e p o r t e d marked i n h i b i t i o n of germination and corresponding y i e l d r e d u c t i o n f o r row crops p l a n t e d t o s o i l s r e c e i v i n g crude o r waste o i l a p p l i c a t i o n s i n excess of
2 % b y weight P a l and Overcash (1978) r e p o r t e d t h a t t h e growth of v e g e t a b l e s and row crops w e r e a f f e c t e d a t an
In a study by Bulman and Scroggins (1988), it was found that plant growth was optimal in field plots with an oil content of 3.5% or less, while growth declined significantly in plots with over 5% oil Additionally, the application of 1% and 2% oil in the soil resulted in reduced crop growth during the first season Conversely, areas treated with 0.5% oil demonstrated improved crop growth.
Frankenberger and Johanson (1982) reported certain crude oil components and refined petroleum products added to soil at 20% to
60% disrupt the oxidative and soil microflora activity requisite for biological assimilation following oil spillage events with oxidation being slowest for heavier molecules
Research by Miller et al (1980) revealed that a 1% diesel fuel contamination in soil led to significant yield reductions of 49% for beans and 69% for corn, although replanting after four months resulted in nearly normal growth Similarly, Younkin and Johnson (1980) observed a 69% decrease in germination and a 79% reduction in first harvest yield of reed canary-grass in soil with 0.45% diesel fuel, while no yield decrease was noted in the second harvest shortly after diesel addition Overcash and Pal (1979) identified a threshold of approximately 1% oil content in soil for reduced yields, with levels between 1.5% and 2% causing declines greater than 50% Additionally, early investigations dating back to 1919 indicated that oil damage in soil was primarily attributed to poor aeration and water interaction Table 2 provides an overview of oil tolerance for selected crops (Overcash and Pal, 1979).
These effects occur immediately after application
Research indicates that the phytotoxic response to soil contamination by petroleum hydrocarbons is influenced more by the release of iron and manganese under anaerobic conditions than by direct toxicity (Carr, 1919; Ellis and Adams, 1961) Notably, this phytotoxicity decreases after the hydrocarbons are assimilated by the soil.
Table 2 O i l Tolerance for Selected Crops
Crop Type Single O i l Application yams, carrots, rape, c 0.5% of soil weight lawngrasses, sugar beets ryegrass, oat, barley, corn, wheat, beans, soybeans, tomato red clover, peas, cotton potato, sorghum
< 3.0% of soil weight perennial grasses, > 3.0% of soil weight coastal bermuda grass, trees, plantain
These studies indicate that under hydrocarbon loadings >1%,
E&P wastes can negatively impact plant growth, but existing data suggests that when mixed hydrocarbons are present at 1% or less, there is minimal to no reduction in yield This finding supports the decision to set the 1% threshold Additionally, it is anticipated that the site will recover within a few months to one growing season after a single application.
Oil mobility in soil significantly impacts the assessment of potential groundwater contamination Plice (1948) noted that when oil infiltrates the soil, heavier, more viscous compounds tend to remain near the surface, while lighter fractions penetrate deeper Additionally, although overall concentrations of oil decrease with depth, the composition shifts towards a higher presence of lighter aromatic fractions (Duffy et al., 1977; Weldon, 1978).
A recent EPA review (1987) highlighted that produced waters from E & P wastes contain significant levels of mobile hydrocarbons, such as benzene, toluene, ethyl benzene, and xylenes (Roy and Griffin, 1985) While these compounds are found in diesel oil-based drilling fluids, their concentrations are low enough to be effectively attenuated in subsurface strata through adsorptive mechanisms (El-Dib et al., 1978) Additionally, their mobility is further limited by the chromatographic effects within porous media (Waarden, Groenewoud, and Bridie, 1977).
Oil floats, and its movement through soils is restricted to those of liquids moving
A P I P U B L x 4 5 2 7 9 3 W 0732290 05L7l127 9 2 b W pores of passable diameter, not saturated with water Movement is further retarded by the IIJarnin effect1' or obstruction of a non-wetting fluid in a porous media (Schiegg, 1980)
Research indicates that low levels of hydrocarbon addition to surface soils do not pose significant leaching issues Studies by Watts et al (1982) showed no migration at depths of 30 to 45 cm after applying 14% industrial waste oil to the top 15 cm Similarly, Raymond et al (1976) found that 99% of 2% oil added to the top 15 cm remained within the top 20 cm after one year Streebin et al (1985) reported no significant oil migration with loading rates of 3% and 13% of soil weight per year Oudot et al (1989) concluded that the potential for leaching unmodified hydrocarbons toward groundwater was minimal at a 2% oil loading Therefore, the recommended one-time addition of 1% production waste to soil is unlikely to cause leaching problems.
It has been demonstrated that soils have an adequately diverse microbial population and capacity to degrade E&P waste hydrocarbons (Raymond et al., 1967; Atlas and Bartha, 1972;
Jobson et al., 1972; Kincannon, 1972; Westlake et al., 1974;
Saturates and light-end aromatics are the first components to undergo degradation, with the rate of this process influenced by factors such as hydrocarbon concentration and composition, nutritive status, aeration, moisture, and temperature.
Meyers, 1978; Dibble and Bartha, 1 9 7 9 ; Brown e t a l , 1983; Flowers e t a l , 1984; Bleckmann e t a l , 1 9 8 9 ) Mechanisms and pathways of b i o d e g r a d a t i o n of petroleum hydrocarbons a r e q u i t e complex and a r e beyond t h e scope of t h i s p a p e r S u f f i c e it t o say t h a t t h e narrower t h e c a r b o n : n i t r o g e n r a t i o ( 6 0 - 1 0 0 C : N ) and t h e n e a r e r t h e m o i s t u r e and t e m p e r a t u r e a r e t o optimum l e v e l s (60-80% of t h e m o i s t u r e r e t a i n e d i n s o i l a t 0.33 b a r p r e s s u r e and 35-38'C, r e s p e c t i v e l y ) , t h e g r e a t e r t h e r a t e of d e g r a d a t i o n
Watts e t a l (1982) measured a 2-year h a l f l i f e f o r a 1 4 % by volume l o a d i n g of o i l t o s o i l S t r e e b i n e t a l (1985) a l s o found a h a l f l i f e of about 2 y e a r s f o r A P I s e p a r a t o r sludge a t a s i m i l a r l o a d i n g r a t e A t a l o a d i n g r a t e of 2 % i n t h e f i e l d , 9 4 % of hydrocarbons w e r e removed a f t e r 3 5 y e a r s (Oudot e t a l , 1 9 8 9 )
Lynch and Genes (1987) determined a h a l f l i f e of 7 7 days on a f i e l d p l o t c o n t a i n i n g up t o 1% polyaromatic hydrocarbons i n s o i l with 5% benzene e x t r a c t a b l e hydrocarbons
I t h a s b e e n demonstrated t h a t d e g r a d a t i v e p r o c e s s e s a t t e n u a t e t h e more mobile, l i g h t - e n d aromatic and water-soluble petroleum hydrocarbons when a p p l i e d t o t h e s u r f a c e with l i t t l e p o t e n t i a l f o r contaminant m i g r a t i o n (Raymond, 1 9 7 5 ; Brown e t a l , 1983; Brown and D e u e l , 1983; W h i t f i l l and Boyd, 1 9 8 7 ; Bleckmann e t a l , 1 9 8 9 )
W h i t f i l l and Boyd (1987) r e p o r t e d t h a t s o i l s may be t r e a t e d with up t o 5 % o i l by weight with no adverse environment impact
The API Environmental Guidance Document establishes a 1% oil and grease threshold for the land disposal of exploration and production (E&P) wastes, based on the attenuation and degradation processes that occur during landspreading This threshold is grounded in the principle of minimum management, allowing operators to mix E&P waste with soil at a ratio that does not exceed 1% oil and grease Evidence suggests that this 1% hydrocarbon by weight is a reasonable limit, resulting in only temporary reductions in plant yields.
Pit Operations and Land Disposal
Pit Operations
The migration of contaminants from waste drilling fluids stored in earthen pits is significantly restricted by the effective sealing provided by dispersed particulates (Rowsell et al., 1985).
Drilling muds, primarily composed of clay-water suspensions, serve multiple essential functions, including cleaning cuttings from the drill bit, stabilizing the borehole, and lubricating the drill string A considerable amount of this mud, along with drill cuttings, is circulated to the reserve pit as waste The interaction between the mud and cuttings with the natural earthen surface of the pit walls and bottom creates a seal, forming a natural liner system The efficiency of this sealing process increases with the clay content and the smaller pore diameter of the native soil.
Clay and fine silt particles
The author notes that pits built in coarser textured soils, as well as loamy or clayey soils under arid conditions, allow waste drilling fluids to penetrate deeper compared to those in moist loamy or clayey soils The natural liner formed by these soil layers acts as both a physical barrier and possesses chemisorptive properties, necessitating a higher concentration of fine particulates for effective development.
A P I PUBLm4527 93 = 0732290 0 5 L 7 L 3 L 357 reducing the potential for pollutant migration
Prewetting the surfaces of pits in coarse-textured, loamy, or clayey soils with vertical cracks can minimize penetration depth and reduce the quantity of fine particulates required for an effective natural liner seal.
Pit liquid is defined as the aqueous phase above settled solids The API Environmental Guidance Document recommends an operative criteria of 4 mmho/cm ( 2 4 5 2 mg/liter TDS for riA1r =
EC is a key index parameter used for decision-making regarding pit liquid disposal options It is important to note that analyses of pit liquids do not provide a complete picture of the pit solids; separate analyses are necessary to fully understand the contents of the pit For parameter definitions and a comparative discussion, refer to Section 2.2.1.
Collecting multiple grab samples at different depths enhances the statistical likelihood of acquiring a representative sample It is essential to use containers that can be opened below the surface at specific depth intervals when sampling multiphase liquids, such as an oil layer over water.
Expensive sampling equipment is usually not necessary and more often than not fails under field trials Scrupulous clean- ing of sampling hardware is requisite in preventing cross
The specific analytical protocol is given in the Appendix
The EC criteria may be relaxed (subject to state and local regulations) where the native soil or freshwater wetlands are of poorer quality than the wastes themselves
Pit liquids nearing threshold criteria should only be applied to agricultural soils as a one-time application, accompanied by careful management of sodium levels This management must include, at the very least, a laboratory bench-scale equilibrium study to determine an acceptable loading rate and a contingency plan for reclaiming saline-sodic soils.
To ensure proper land disposal of pit solids, it is essential to measure EC, SAR, ESP, and O&G, adhering to guidance values of 4 mmho/cm, 12%, 15%, and i%, respectively Recommended disposal methods include burial, landfill, and landspreading, while roadspreading is not advised for pit solids.
EC and O&G are operative parameters for materials buried or landfilled EC, O&G, S A R and ESP are used for managing waste disposal by landspreading
Sampling pit solids involves inserting a hollow tube, open at both ends, into the solids to ensure the sample accurately represents the entire matrix For earthen pits, sampling is conducted down to the consolidated native soil, while lined pits are sampled up to the top of the liner Typically, an end cap or a suitable plugging device is used to create back suction, which helps retain the sample within the core barrel during retrieval.
To effectively sample a large pit, it is recommended to divide it into sections of approximately 5000 ft² each These sections can be composited to create a section sample, which may be analyzed individually and averaged to represent the pit solids, or combined by weight or volume before analysis.
E&P waste:soil mixtures are sampled after closure to verify correct landspreading procedures Multiple corings are made for preparing composites representative of the zone of incorporation
A minimum of 10 cores are then taken in each
Analytical protocols specific for each parameter are de- tailed in the attached Appendix
The primary challenge in managing exploration and production (E&P) wastes through landspreading is the presence of salt (NaCl) While sodicity, measured by the Sodium Adsorption Ratio (SAR) for pore liquids and the Exchangeable Sodium Percentage (ESP) for solids, poses significant concerns, it can be effectively controlled with calcium amendments such as gypsum, provided that total salt levels are maintained Additionally, petroleum hydrocarbons, as part of oil and gas operations, require careful management.
A P I PUBL*4527 9 3 m 0732290 0517134 Obb m natural environment by the landspreading technique
In practice, E&P waste solids are added to the receiving soil then disked to an appropriate depth such that the final waste:soil mixture meets the constituent threshold criteria
Landspreading is most effective in the humid and warmer regions of the country, where annual precipitation exceeds 25 inches, as higher rainfall provides a greater margin for error However, managing E&P waste solids for spreading and mixing poses challenges, often leading to the formation of "hot spots." While organic materials will decompose, salts necessitate leaching through rainfall to be removed from the root zone Additionally, amendments aimed at improving sodic soil conditions require substantial soil moisture to facilitate cation exchange and displace desorbed sodium.
Burial or landfill is best suited to a semi-arid (rainfall <
In semi-arid regions, the recommended criteria for environmental impact may be relaxed after a thorough site evaluation, particularly in areas with an annual precipitation of 20 inches or less, where leaching to the subsurface is unlikely.
Summary of Guideline Thresholds and
A summary of guideline thresholds and application relative to waste type, method of disposal, and criteria is given in Table
E&P waste is categorized into liquid and solid phases In semi-arid regions, these wastes typically do not provide a suitable weight-bearing or driving surface, making road spreading an unsuitable method for disposing of pit solids.
Pit solids may have utility as construction fill in arid
A P I PUBL*4527 9 3 0732270 0 5 3 7 3 3 5 T T 2 spreading applications are defined in the A P I Environmental Guidance Document
Table 3 Summary of E&P Waste, Disposal Technique, and Operative Criteria
Liquid roadspreading 4 NA* N A NA landspreading 4 12 15 1
Solids landspreading 4 burial or landfill 4
3 3 Flow Diagram for Pit Liquid Disposal
Meet Criteria? Pit Liquid Disposal
3 4 Flow Diagram for Pit Solids
Meet Closure Yes Backfill Pit
Yes Mix Solids with Native Soil
Parameters and Example Calculations
3.5.1 Pit Material and Native S o i l Characteristics
Pit++ Pit* Native* Threshold# Parameter+ Liquid Solids Soil Level
+Parameters are reported on a dry weight basis unless noted otherwise
++NA means the parameter meets the guidance threshold or is not applicable for that matrix
Soluble constituents were determined for saturated paste extracts of pit solids and native soil
#An ESP of 12% is recommended in establishing land
Comparison of pit liquid analyses and threshold values show no chemical limitation for land application
Native soil loading capacity f o r Na using an ESP of 12%, and materials distribution depth of 6 in/acre
Na, mg/kg = CEC meq/100g X (ESP/100) X 23 mg/meq X 10
Na, lb/acre-6 in = 1093 mg Na/kg soil X 2
Total Na mass of pit liquid
Na,lb = (9.3 m e w 1 X 23 mg/meq X 3.8 l/gal X 42 gal/bbl
Land requirement on Na mass basis, assuming a materials distribution to a depth of 6 in
Acres = (973 lb Na) / (2186 lb Na/acre-6 in)
Pit liquid, acre-in = (12,938 bbl X 42 gal/bbl) /
Native soil has an infiltration rate of 1.12 in/hr but drops to less than 0.1 in/hr within 10 min A dry surface can receive about 1.3 in without producing runof f
A P I PUBL*4527 93 = 0 7 3 2 2 9 0 0517L4L 2Tb g) Acreage needed for a one-time application so as not to generate runoff
Land needed, acre = 20 acre-in/l.3 in application
= 15.4 h) Construction of temporary levees for containment during infiltration reduces land requirement
3.5.2.2 Pit Solids Management a) Comparison of pit solid analyses and recommended thresholds show EC, S A R , ESP and O K as potential limiting constituents b) Given the fact that the exchangeable Ca is high in both waste solids and the receiving soil, one would not consider SAR limiting c) Pit solids contained 243% moisture (M) on a dry weight basis The equivalent percent water on a wet weight basis is 70.85%
= 29.15% d) Volume of dry solids used to calculate land requirement
Dry solids, bbl = 21,897 bbl wet X 2915
= 6383 e) TDS land requirement (based on relationship from Section 2.2 i)
2452 mg/l = (6383 bbl) (24,830 mg/i) + (X bbl) (272 mg/i)
X bbl = 65522 acre-6 in = (65522 bbl) / (3875 bbl/acre-6 in)
4 mmho/cm = (6383 bbl) (40.5 mmho/cm) + (X bbl) (0.4 mmho/cm) / (6383 bbl + X bbl)
X bbl = 64717 acre-6 in = (64717 bbl) / (3875 bbl/acre-6 in)
X bbl = 4667 acre-6 in = (4667 bbl) / (3875 bbl/acre-6 in)
X bbl = 64539 acre-6 in = (64539 bbl) / (3875 bbl/acre-6 in)
= 16.7 i) The land-limiting constituent is EC, requiring 64717 bbl of native soil to effect management (EC