Arjmandi, Masoud Friday, September 10, :30 PM Mathews, Barbara FW: Upper Southwest ADEQ Request2 for Sand Variance-lp

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1 Mathews, Barbara From: Sent: To: Subject: Attachments: Arjmandi, Masoud Friday, September 10, :30 PM Mathews, Barbara FW: Upper Southwest ADEQ Request2 for Sand Variance-lp pdf -----Original Message----- From: Lance Powell Sent: Thursday, September 09, :46 PM To: Arjmandi, Masoud Cc: Leamons, Bryan; 'Jeff Barfield' Subject: Upper Southwest Masoud, Rec d Digitally AFIN: S1-R1 PMT#: By Barbara Mathews at 8:52 am, Sep 13, DOC ID#: TO: MA> file On behalf of the Upper Southwest Arkansas Regional Solid Waste Management District, Civil Engineering Associates, LLC is submitting the attached information associated with their Class 1 landfill. Thanks, Lance Powell, P.E. CIVIL ENGINEERING ASSOCIATES 2114 East Matthews Ave. Jonesboro, Arkansas Phone: (870) Fax: (870) Mobile: (870) S W M D 1

2 2114 East Matthews Avenue Jonesboro, Arkansas Fax September 9, 2010 Arkansas Department of Environmental Quality Solid Waste Management Division Attn: Mr. Masoud Arjmandi 5301 Northshore Drive North Little Rock, Arkansas SUBJECT: Request for Alternate Leachate Drainage Layer Material Upper Southwest Arkansas Regional Solid Waste Management District Solid Waste Permit No S1-R1; AFIN ADEQ Document Reference Identifiers: and Dear Mr. Arjmandi, In accordance with Arkansas Department of Environmental Quality (ADEQ) Regulation (b) (2), Civil Engineering Associates, LLC (CEA) submitted a request to the ADEQ for a variance from the grain size distribution testing requirement of ADEQ Regulation (b) (1), for the referenced facility. As you are aware, the request was denied by the ADEQ in a letter dated September 1, On behalf of the Upper Southwest Arkansas Regional Solid Waste Management District (USARSWMD), CEA is asking the ADEQ to reconsider the request dated August 26, 2010 based on the enclosed information. ADEQ Regulation (c) states that calculations or demonstrations must be provided to show that the leachate collection system will adequately dewater the waste mass and that clogging of the system will not occur. The primary reason for the grain size distribution requirement of Regulation (b) (1) is to avoid the potential for clogging of the underlying leachate collection system. The enclosed Geotextile Filter Fabric Design and Clogging Potential Calculations demonstrate that a geotextile material for use around the leachate collection pipe can be selected to use with the material being proposed for the leachate drainage layer at the USARSWMD Class 1 Landfill. The grain size distribution of a sample of the actual sand proposed to be used was entered into the design software for selection of the appropriate geotextile material. The sand sample used for the calculations had 8.0 percent by weight passing the No. 200 sieve. Other grain size distribution testing that has been performed on the proposed sand by the USARSWMD has indicated typically 5 to 10 percent by weight finer than the No. 200 Sieve. The results of these tests are included with the calculations. As previously stated, the USARSWMD is requesting that the ADEQ reconsider the request that a maximum of 15 percent by weight passing the No. 200 sieve be allowed as a standard for material being utilized as the leachate drainage layer for the Class 1 landfill. Testing has already demonstrated that the material will meet the ADEQ Regulation (b) permeability requirement of 1 x 10-3 cm/sec. In regard to the concern indicated in the September 1, 2010 letter that lab results and field performance could be quite different, the USARSWMD is proposing construction testing of the sand material at a rate of one test for every 5,000 cubic yards of material placed, which is not a specific requirement of ADEQ Regulation 22. HOT SPRINGS JONESBORO POPLAR BLUFF

3 Upper Southwest Arkansas Regional Solid Waste Management District Class 1 Landfill Page 2 CEA appreciates the ADEQ s consideration of this request. If you have any questions or need additional information, please contact me at (870) Sincerely, CIVIL ENGINEERING ASSOCIATES, LLC Lance Powell, P.E. Project Manager Enclosure cc: Max Tackett (USARSWMD) Jeff Barfield (USARSWMD) HOT SPRINGS JONESBORO POPLAR BLUFF

4 CALCULATION SUMMARY SHEET PROJECT Upper Southwest Arkansas Regional Solid Waste Management District Class 1 Landfill CALCULATION TITLE Geotextile Filter Fabric Design and Clogging Potential Calculations PROJECT NO. SW CALCULATION NO. 1 ORIGINATED BY Lance Powell, P.E. DATE 09/08/10 CHECKED BY Lance Powell, P.E. DATE 09/08/10 SUBJECT: The following calculations evaluate the potential for geotextile clogging as the basis for the design of the leachate collection system. This information provides the basis for construction technical specifications for the geotextile and leachate drainage layer materials to be used for future cell construction at the Upper Southwest Arkansas Regional Solid Waste Management District (USARSWMD) Class 1 Landfill. DESCRIPTION OF PROBLEM: The purpose of the geotextile filter fabric is to protect the leachate collection piping system while minimizing intrusion (clogging) from adjacent soil layers. This filter layer must be able to perform three functions. (i) The filter must prevent passage of significant amounts of soil; (ii) The filter must have a relatively high hydraulic conductivity; (iii) The soil particles in contact with the filter must not migrate significantly into the adjacent drainage layer. Methods used to design the geotextile fabrics to be used at the USARSWMD Class 1 Landfill in conjunction with the proposed leachate drainage layer material, are based on methods developed by the Nicolon Corporation and Mirafi. These methods are widely used and accepted in the industry. The Mirafi Geotextile Filter Design, Application, and Product Selection Guide is enclosed for reference. The design guide was used in conjunction with Mirafi s Geofilter 32 design software to prepare the enclosed calculations.

5 SUMMARY: Specifications for the leachate collection system components involving geotextiles shall consider the following minimum standards based on the enclosed calculations: 1. The geotextile shall have a minimum permeability of 8.4 x 10-3 cm/s; 2. The geotextile shall have an Apparent Opening Size that is less than 0.21 mm. 3. The geotextile percent open area shall be 4-6% for woven geotextiles and the porosity shall be at least 30%. 4. Geotextile fabric shall be a Mirafi 160N or equivalent. In addition to the above conditions, the geotextile shall adhere to the following minimum specifications: Grab Strength (lbs): 160 Sewn Seam Strength (lbs) 145 Elongation (%): 50 Puncture Strength (lbs): 60 Burst Strength (psi): 190 Trapezoidal Tear (lbs): 60 SOURCES OF DATA: Hari D. Sharma and Sangeeta P. Lewis. Waste Containment Systems. Waste Stabilization, and Landfills, John Wiley & Sons, Inc, Donald H. Gray, Robert M. Koerner, and Xuede Qian. Geotechnical Aspects of Landfill Design and Construction, Prentice Hall, Mirafi Geotextile Filter Design, Application, and Product Selection Guide (See Enclosed) Geofilter 32 Design Software INTENDED USE: PRELIMINARY CALC. FINAL CALC. SUPERCEDES CALC NO. OTHER REV NO DESCRIPTION BY DATE CHK DATE Geotextile filtration involves the movement of liquid through a geotextile fabric layer. At the same time, the fabric serves the purpose of retaining the soil on its upstream side. As such, both adequate permeability and soil retention are required simultaneously. As noted by Mirafi, filtration is summarized by the following two conflicting requirements: The filter must retain soil, implying that the size of filter pore spaces or openings should be smaller than a specified maximum value; and

6 The filter must be permeable enough to allow a relatively free flow through it, implying that the size of filter porte spaces and the number of openings should be larger than a specified minimum value. In designing geotextile filter fabrics to be used at the USARSWMD Class 1 Landfill, the following considerations were evaluated in accordance with the methodology recommended by Mirafi: Retention; Permeability; Anti-clogging; Survivability; and Durability. STEP 1: APPLICATION FILTER REQUIREMENTS Geotextile fabric materials to be used at the USARSWMD Class 1 Landfill will generally be associated with the leachate collection and removal systems for the individual waste disposal cells. The geotextiles will be used to wrap the leachate collection pipe and gravel bedding material. Based on the above intended use, the drainage media adjacent to the geotextile will consist of washed gravel bedding leachate collection pipes. As noted in the Mirafi design guide, permeability and anti-clogging are favored in applications where the geotextile filter fabric will wrap collection pipe and gravel bedding. STEP 2: BOUNDARY CONDITIONS The applications described in Step 1 will generally involve situations where large confining stress conditions are inherently present. In other words, in most applications, the geotextile filter fabric will be situated under many layers of municipal solid waste and earthen material. The high confining stress could result in the following and must be considered in the design and selection of the filter media: High confining pressures tend to increase the relative density of coarse grained soil, increasing the soil s resistance to particle movement. This affects the selection of retention criteria. High confining pressures decrease the hydraulic conductivity of fine grained soils, increasing the potential for soil to intrude into, or through the geotextile filter. High confining pressures increase the potential for the geotextile and soil mass to intrude into flow paths reducing flow capacity within the drainage media, especially when geosynthetic drainage cores are used.

7 Flow conditions for the design of the geotextile components at the USARSWMD Class 1 Landfill are best epresented by steady state flow conditions for the purpose of these calculations. STEP 3: SOIL RETENTI ON REQUIREMENTS The particle size of the adjacent soil materials provide the basis for determining the retentionn criteria for the filter fabric design. As shown in the Mirafi design guide the chart below for steady state flow conditions is used to determine the apparent opening size.

8 The soils in contact with the geotextile fabric at the USARSWMD Class 1 Landfill will generally consist of soils with 5 to 10% fines passing the No. 200 Sieve. The particle size distribution of the sand proposed to be in contact with the geotextile, based on laboratory analysis, was entered into the Geofilter design software to determine the maximum allowable geotextile opening size. It was determined that an apparent opening size of O 95 not more than 0.21 mm is required for the given applications at the USARSWMD Class 1 Landfill. The results from the grain size distribution testing of the sand, as well as additional sieve analysis with the No. 200 Sieve specifically, are attached with these calculations. STEP 4: GEOTEXTILE PERMEABILITY REQUIREMENTS The minimum allowable permeability of the geotextile is based on the requirement that the permeability of the geotextile must be greater than the permeability of the overlying soil. A permeability of 1X10-3 cm/sec is assumed for the overlying soil. However, this value should be confirmed during the construction of the leachate drainage layer. The geotextile permeability is affected by the filter application, flow conditions, and soil type. Based on Giroud, 1988, the following formula can be used to determine the minimum geotextile permeability: K g > i s k s From Table 1 (See Mirafi Design Guide), a gradient of 1.5 is recommended for leachate collection and removal system designs. Therefore K g > (1.5) x (1.0 x 10-3 cm/s) K g > 1.5 x 10-3 cm/s It is important to recognize that many of the geotextile laboratory test properties represent ideal conditions and thereby result in artificially high numeric values when used in design. As such, a laboratory test value can not generally be used directly and must be modified for in-situ conditions. To compensate for the difference between laboratory measured values and true performance values the following reduction factors have been utilized (Gray,2002): Soil Clogging and Blinding Reduction Factor 5.0 Creep Reduction of Void Space Reduction Factor 1.5 Reduction Factor for adjacent material intruding into geosynthetic void spaces 1.0 Chemical Clogging Reduction Factor 1.5 Biological Clogging Reduction Factor 5.0 As such, the allowable minimum property for hydraulic conductivity of the geotextile is 8.4 x 10-3 cm/s (1.5 x 10-3 cm/s x 5.0 x 1.5 x 1.0 x 1.5 x 5).

9 When evaluating suitability of various geotextiles, the permeability can be derived by multiplying the permittivity of the geotextile times the thickness. STEP 5: ANTI-CLOGGING REQUIREMENTS Clogging can be minimized by adhering to the following criteria: Use the largest opening size (O95) that satisfies the retention criteria. For nonwoven geotextiles, use the largest porosity available, never less than 30%. For woven geotextiles, use the largest percentage of open area available, never less than 4%. STEP 6: SURVIVABILITY REQUIREMENTS Geotextiles can be damaged during construction depending on how they are placed and the materials adjacent to the geotextile fabric. Construction survivability can be assured by specifying the minimum strength properties that fit with the severity of the installation. Table 2 in the Mirafi Design Guide provides recommendations for various applications. Assuming a subsurface application with high contact stresses, the following strength requirements are recommended (AASHTO, 1996): Grab Strength (lbs): 160 Elongation (%) 50 Sewn Seam Strength (lbs): 145 Puncture Strength (lbs): 60 Burst Strength (lbs): 190 Trapezoidal Tear (lbs): 60 To allow for the required flow through the geotextile, void spaces must be sufficiently large. However, soil and waste particles should not pass through the fabric with the flowing liquid. This leads to a situation where finer soil particle increase until the upper gradient soil collapses. The result will be a minute sinkhole type pattern that grows larger with time. This undesired process can be prevented by making geotextile voids small enough to retain the soil. STEP 7: DURABILITY REQUIREMENTS Geotextiles are susceptible to UV deterioration if exposed to sunlight for extended periods. The geotextile applications planned for the USARSWMD Class 1 Landfill generally will not require extended periods of UV exposure. Geotextiles made from polyprobylene are generally inert to most naturally occurring chemicals. A Mirafi 160N or equivalent non-woven geotextile fabric is recommended for the conditions described herein. A product data sheet for the Mirafi 160N is attached for reference.

10 ATTACHMENTS

11 Marine & Transportation Engineering geotextile filter design, application, and product selection guide

12 GEOTEXTILE FILTER DESIGN, APPLICATION, AND PRODUCT SELECTION GUIDE Drainage and Erosion Control Applications TABLE OF CONTENTS Introduction and Explanation of the Problem... 1 The Mirafi Solution... 1 Systematic Design Approach... 2 Step One: Application Filter Requirements... 3 Step Two: Boundary Conditions... 3 Step Three: Soil Retention Requirements... 4 Step Four: Geotextile Permeability Requirements... 5 Step Five: Anti-Clogging Requirements... 6 Step Six: Survivability Requirements... 7 Step Seven: Durability Requirements... 7 Geotextile Filter Selection Guide... 8 Geotextile Filter Minimum Average Physical Properties Chart... 10

13 INTRODUCTION AND EXPLANATION OF THE PROBLEM Drainage Aggregate trench and blanket drains are commonly used to drain water from surrounding soils or waste materials. These drains are typically installed less than three feet deep. They may be at greater depths in situations where there is a need to significantly lower the groundwater table or to drain leachate. In loose or gap graded soils, the groundwater flow can carry soil particles toward the drain. These migrating particles can clog drainage systems. Erosion Control Stone and concrete revetments are often used on waterway slopes to resist soil erosion. These armored systems, when placed directly on the soil, have not sufficiently prevented erosion. Fluctuating water levels cause seepage in and out of embankment slopes resulting in the displacement of fine soil particles. As with trench drains, these fine soil particles are carried away with receding flows. This action eventually leads to undermining of the armor system. Typical Solutions Specially graded fill material which is intended to act as a soil filter is frequently placed between the drain or revetment and the soil to be protected. This graded filter is often difficult to obtain, expensive to purchase, time consuming to install and segregates during placement, thus compromising its filtration ability. Drainage Erosion Control Geotextile filters retain soil particles while allowing seeping water to drain freely. Fine soil particles are prevented from clogging drainage systems. Geotextile filters retain soil particles while allowing water to pass freely. Buildup of hydrostatic pressures in protected slopes is prevented, thus enhancing slope stability. THE MIRAFI SOLUTION Filtration geotextiles provide alternatives to graded filters. Designing with Geotextile Filters Geotextiles are frequently used in armored erosion control and drainage applications. Some of the most common applications include slopes, dam embankments/spilllways, shorelines armored with riprap, flexible block mats and concrete filled fabric formed systems. Drainage applications include pavement edge drains, french drains, prefabricated drainage panels and leachate collection/leak detection systems. In all of the above applications, geotextiles are used to retain soil particles while allowing liquid to pass freely. But the fact that geotextiles are widely used where their primary function is filtration, there remains much confusion about proper filtration design procedures. For this reason, Mirafi commissioned Geosyntec Consultants, Inc. to develop a generic Geotextile Filter Design Manual. The manual offers a systematic approach to solving most common filtration design problems. It is available to practicing designers exclusively through Mirafi. This Geotextile Filter Design, Application, and Product Selection Guide is excerpted from the manual. 1

14 Mechanisms of Filtration A filter should prevent excessive migration of soil particles, while at the same time allowing liquid to flow freely through the filter layer. Filtration is therefore summarized by two seemingly conflicting requirements. The filter must retain soil, implying that the size of filter pore spaces or openings should be smaller than a specified maximum value; and The filter must be permeable enough to allow a relatively free flow through it, implying that the size of filter pore spaces and number of openings should be larger than a specified minimum value. Geotextile Filter Requirements Before the introduction of geotextiles, granular materials were widely used as filters for geotechnical engineering applications. Drainage criteria for geotextile filters is largely derived from those for granular filters. The criteria for both are, therefore, similar. In addition to retention and permeability criteria, several other considerations are required for geotextile filter design. Some considerations are noted below: Retention: Ensures that the geotextile openings are small enough to prevent excessive migration of soil particles. Permeability: Ensures that the geotextile is permeable enough to allow liquids to pass through without causing significant upstream pressure buildup. Anti-clogging: Ensures that the geotextile has adequate openings, preventing trapped soil from clogging openings and affecting permeability. Survivability: Ensures that the geotextile is strong enough to resist damage during installation. Durability: Ensures that the geotextile is resilient to adverse chemical, biological and ultraviolet (UV) light exposure for the design life of the project. The specified numerical criteria for geotextile filter requirements depends on the application of the filter, filter boundary conditions, properties of the soil being filtered, and construction methods used to install the filter. These factors are discussed in the following step-by-step geotextile design methodology DESIGN APPROACH 2 SYSTEMATIC Design Methodology The proposed design methodology represents years of research and experience in geotextile filtration design. The approach presents a logical progression through seven steps. Step 1: Define the Application Filter Requirements Step 2: Define Boundary Conditions Step 3: Determine Soil Retention Requirements Step 4: Determine Permeability Requirements Step 5: Determine Anti-Clogging Requirements Step 6: Determine Survivability Requirements Step 7: Determine Durability Requirements

15 STEP ONE: DEFINE APPLICATION FILTER REQUIRE- MENTS Geotextile filters are used between the soil and drainage or armoring medium. Typical drainage media include natural materials such as gravel and sand, as well as geosynthetic materials such as geonets and cuspated drainage cores. Armoring material is often riprap or concrete blocks. Often, an armoring system includes a sand bedding layer beneath the surface armor. The armoring system can be considered to act as a drain for water seeping from the protected slope. Identifying the Drainage Material The drainage medium adjacent to the geotextile must be identified. The primary reasons for this include: Large voids or high pore volume can influence the selection of the retention criterion Sharp contact points such as highly angular gravel or rock will influence the geosynthetic survivability requirements. Retention vs. Permeability Trade-Off The drainage medium adjacent to the geotextile often affects the selection of the retention criterion. Due to the conflicting nature of filter requirements, it is necessary to decide whether retention or permeability is the favored filter characteristic. For example, a drainage material that has relatively little void volume (i.e., a geonet or a wick drain) requires a high degree of retention from the filter. Conversely, where the drainage material void volume is large (i.e., a gravel trench or riprap layer), the permeability and anti-clogging criteria are favored. STEP TWO: DEFINE BOUNDARY CONDI- TIONS Evaluate Confining Stress The confining pressure is important for several reasons: High confining pressures tend to increase the relative density of coarse grained soil, increasing the soil s resistance to particle movement. This affects the selection of retention criteria. High confining pressures decrease the hydraulic conductivity of fine grained soils, increasing the potential for soil to intrude into, or through, the geotextile filter. For all soil conditions, high confining pressures increase the potential for the geotextile and soil mass to intrude into the flow paths. This can reduce flow capacity within the drainage media, especially when geosynthetic drainage cores are used. Define Flow Conditions Flow conditions can be either steady-state or dynamic. Defining these conditions is important because the retention criteria for each is different. Examples of applications with steady-state flow conditions include standard dewatering drains, wall drains and leachate collection drains. Inland waterways and shoreline protection are typical examples of applications where waves or water currents cause dynamic flow conditions. 3

16 STEP THREE: DETERMINE SOIL RETENTION REQUIREMENTS Charts 1 and 2 indicate the use of particle-size parameters for determing retention criteria. These charts show that the amount of gravel, sand, silt and clay affects the retention criteria selection process. Chart 1 shows the numerical retention criteria for steady-state flow conditions; Chart 2 is for dynamic flow conditions. For predominantly coarse grained soils, the grainsize distribution curve is used to calculate specific parameters such as C u, C' u, C c, that govern the retention criteria. Chart 1. Soil Retention Criteria of Steady-State Flow Conditions MORE THAN 20% CLAY d 20 < 0.002mm NON-DISPERSIVE SOIL (DHR < 0.5) DISPERSIVE SOIL (DHR > 0.5) O 95 < 0.21MM USE 3 TO 6 INCHES OF VERY FINE SAND BETWEEN SOIL AND GEOTEXTILE, THEN DESIGN THE GEOTEX- TILE AS A FILTER FOR THE SAND LESS THAN 20% CLAY, and MORE THAN 10% SILT PLASTIC SOIL Pl > 5 FROM SOIL PROPERTIES TESTS NOTES: d x = LESS THAN 10% SILT, and MORE THAN 10% SAND (d 10 > 0.07mm and d 10 < 4.8mm) MORE THAN 90% GRAVEL d 10 > 4.8mm (d 20 > 0.002mm and d 10 < 0.07mm) particle diameter of which size x percent is smaller d 100 C u = d 0 where: APPLICATION FAVORS RETENTION APPLICATION FAVORS PERMEABILITY STABLE SOIL (1 C c 3) UNSTABLE SOIL (C c > 3 or C c < 1 ) d 100 and d 0 are the extremeties of a straight line drawn through the particle-size distribution, as directed above and d 50 is the midpoint of this line USE USE d 60 d 30 d 30 d 10 C u C u USE TANGENT AT d 50 C u C c = I D Pl DHR O 95 = = = = NON-PLASTIC SOIL Pl < 5 (d 30 ) 2 d 60 X d 10 WIDELY GRADED C u > 3 UNIFORMLY GRADED C u < 3 relative density of the soil plasticity index of the soil double-hydrometer ratio of the soil geotextile opening size LOOSE (I D < 35%) MEDIUM (35% < I D < 65%) DENSE (I D > 65%) LOOSE (I D < 35%) MEDIUM (35% < I D < 65%) DENSE (I D > 65%) O 95 < O 95 < 13.5 C u d 50 O 95 < 9 C u d C u d 50 O 95 < C u d 50 O 95 < 1.5 C u d 50 O 95 < 2 C u d 50 4

17 Chart 2. Soil Retention Criteria of Dynamic Flow Conditions MORE THAN 20% CLAY d 20 < 0.002mm NON-DISPERSIVE SOIL (DHR < 0.5) DISPERSIVE SOIL (DHR > 0.5) O 95 < 0.21MM USE 3 TO 6 INCHES OF VERY FINE SAND BETWEEN SOIL AND GEOTEXTILE, THEN DESIGN THE GEOTEX- TILE AS A FILTER FOR THE SAND LESS THAN 20% CLAY, and MORE THAN 10% SILT PLASTIC SOIL Pl > 5 FROM SOIL PROPERTIES TESTS (d 20 > 0.002mm and d 10 < 0.07mm) NON-PLASTIC SOIL Pl < 5 NOTES: LESS THAN 10% SILT, and MORE THAN 10% SAND (d 10 > 0.07mm and d 10 < 4.8mm) SEVERE WAVE ATTACK MILD WATER CURRENTS C u > 5 O 95 < d 50 d x Pl DHR O 95 C u = = = = = O 95 < 2.5 d 50 and O 95 < d 90 particle diameter of which size x percent is smaller plasticity index of the soil double-hydrometer ratio of the soil geotextile opening size d 60 / d 10 MORE THAN 90% GRAVEL C u < 5 d 50 < O 95 < d 90 d 10 > 4.8mm Analysis of the soil to be protected is critical to proper filtration design. Define Soil Particle-Size Distribution The particle-size distribution of the soil to be protected should be determined using test method ASTM D 422. The grain size distribution curve is used to determine parameters necessary for the selection of numerical retention criteria. Define Soil Atterberg Limits For fine-grained soils, the plasticity index (PI) should be determined using the Atterberg Limits test procedure (ASTM D 4318). Charts 1 and 2 show how to use the PI value for selecting appropriate numerical retention criteria. Determine the Maximum Allowable Geotextile Opening Size (O 95 ) The last step in determining soil retention requirements is evaluating the maximum allowable opening size (O 95 ) of the geotextile which will provide adequate soil retention. The O 95 is also known as the geotextile s Apparent Opening Size (AOS) and is determined from test procedure ASTM D AOS can often be obtained from manufacturer s literature. STEP FOUR: DETERMINE GEOTEXTILE PERME- ABILITY REQUIRE- MENTS Define the Soil Hydraulic Conductivity (k s ) Determine the soil hydraulic conductivity, often referred to as permeability, using one of the following methods: For critical applications, such as earth dams, soil permeability should be lab measured using representative field conditions in accordance with test procedure ASTM D For non-critical applications, estimate the soil-hydraulic conductivity using the characteristic grain diameter d 15, of the soil (see Figure 2 on the following page). 5

18 STEP FOUR: DETERMINE GEOTEXTILE PERME- ABILITY REQUIRE- MENTS (continued) Figure 2. Typical Hydraulic Conductivity Values Define the Hydraulic Gradient for the Application (i s ) The hydraulic gradient will vary depending on the filtration application. Anticipated hydraulic gradients for various applications may be estimated using Table 1 below. Table 1. Typical Hydraulic Gradients (a) Drainage Applications Typical Hydraulic Gradient Channel Lining 1.0 Standard Dewatering Trench 1.0 Vertical Wall Drain 1.5 Pavement Edge Drain 1.0 Landfill LCDRS 1.5 Landfill LCRS 1.5 Landfill SWCRS 1.5 Shoreline Protection Current Exposure 1.0 (b) Wave Exposure 10 (b) Dams 10 (b) Liquid Impoundments 10 (b) (a) Table developed after Giroud, (b) Critical applications may require designing with higher gradients than those given. Determine the Minimum Allowable Geotextile Permeability (k g ) The requirement of geotextile permeability can be affected by the filter application, flow conditions and soil type. The following equation can be used for all flow conditions to determine the minimum allowable geotextile permeability (Giroud, 1988): k g i s k s Permeability of the geotextile can be calculated from the permittivity test procedure (ASTM D 4491). This value is often available from manufacturer s literature. Geotextile permeability is defined as the product of the permittivity, Ψ, and the geotextile thickness, t g : k g = Ψt g 6

19 STEP FIVE: To minimize the risk of clogging, follow this criteria: DETERMINE ANTI-CLOGGING REQUIREMENTS Use the largest opening size (O 95 ) that satisfies the retention criteria. For nonwoven geotextiles, use the largest porosity available, never less than 30%. For woven geotextiles, use the largest percentage of open area available, never less than 4%. NOTE: For critical soils and applications, laboratory testing is recommended to determine geotextile clogging resistance. STEP SIX: DETERMINE SURVIVABILITY REQUIREMENTS Both the type of drainage or armor material placed adjacent to the geotextile and the construction techniques used in placing these materials can result in damage to the geotextile. To ensure construction survivability, specify the minimum strength properties that fit with the severity of the installation. Use Table 2 as a guide in selecting required geotextile strength properties to ensure survivability for various degrees of installation conditions. Some engineering judgement must be used in defining this severity. Table 2. Survivability Strength Requirements (after AASHTO, 1996) GRAB STRENGTH ELONGATION SEWN SEAM PUNCTURE BURST TRAPEZOID (LBS) (%) STRENGTH (LBS) STRENTH (LBS) STRENTH (LBS) TEAR (LBS) SUBSURFACE DRAINAGE HIGH CONTACT STRESSES (ANGULAR DRAINAGE MEDIA) (HEAVY COMPACTION) or (HEAVY CONFINING STRESSES) LOW CONTACT STRESSES (ROUNDED DRAINAGE MEDIA) (LIGHT COMPACTION) or (LIGHT CONFINING STRESSES) 247 < 50% * > 50% < 50% * > 50% ARMORED EROSION CONTROL HIGH CONTACT STRESSES (DIRECT STONE PLACEMENT) (DROP HEIGHT > 3 FT) LOW CONTACT STRESSES (SAND OR GEOTEXTILE CUSHION) and (DROP HEIGHT < 3 FT) 247 < 50% * > 50% < 50% * > 50% * Only woven monofilament geotextiles are acceptable as < 50% elongation filtration geotextiles. No woven slit film geotextiles are permitted. STEP SEVEN: DETERMINE DURABIL- ITY REQUIREMENTS During installation, if the geotextile filter is exposed to sunlight for extended periods, a high carbon black content and UV stabilizers are recommended for added resistance to UV degradation. Polypropylene is one of the most durable geotextiles today. It is inert to most naturally occurring chemicals in civil engineering applications. However, if it is known that the geotextile may exposed to adverse chemicals (such as in waste containment landfill applications), use test method ASTM D5322 to determine its compatibility. References Giroud, J.P., Review of Geotextile Filter Design Criteria. Proceedings of First Indian Conference on Reinforced Soil and Geotextiles, Calcutta, India, Heerten, G., Dimensioning the Filtration Properties of Geotextiles Considering Long-Term Conditions. Proceedings of Second International Conference on Geotextiles, Las Vegas, Nevada, AASHTO, Standard Specification for Geotextile Specification for Highway Applications, M

20 GEOTEXTILE FILTER FABRIC SELECTION GUIDE SOIL PROPERTIES Silty Gravel w/sand (GM) k s =.005cm/s PI = 0 C c = 2.8 C' u = 34 d' 50 = 3.5mm C u = 211 d 50 = 5.0mm d 90 = 22mm Well-Graded Sand (SW) #1 k s =.005cm/s PI = 0 C c = 1.0 C' u = 9.1 d' 50 =.52mm C u = 8.4 d 50 =.60mm d 90 = 2.7mm Well-Graded Silty Sand (SW) #2 k s =.001cm/s PI = 0 C c = 2.1 C' u = 5.3 d' 50 =.28mm C u = 6.6 d 50 =.28mm d 90 = 1.6mm Silty Sand (SM) k s =.00005cm/s PI = 0 C c = 3.0 C' u = 16.2 d' 50 =.21 C u = 67 d 50 =.22mm d 90 =.95mm (Note: Moderate to Heavy Compaction Required) Soil Retention (1) 1.85 mm 1.03 mm.95 mm.18 mm Permeability 5 x x x x 10-5 Clogging Resistance P.O.A. > 6% P.O.A. > 6% P.O.A. > 6% n > 30% Survivability Req t LOW LOW LOW LOW SUBSURFACE DRAINAGE (2) Gradation Relative Soil Density RECOMMENDED FABRIC Soil Retention (1) Permeability Clogging Resistance Survivability Req t Widely Graded Widely Graded Widely Graded Widely Graded Dense Dense Dense Medium FILTERWEAVE 400 FILTERWEAVE 400 FILTERWEAVE 400 MIRAFI 180N.93 mm.51 mm.48 mm.18 mm 5 x x x x 10-5 P.O.A. > 6% P.O.A. > 6% P.O.A. > 6% n > 30% HIGH HIGH HIGH HIGH Gradation Widely Graded Widely Graded Widely Graded Widely Graded Relative Soil Density Loose Loose Loose Medium RECOMMENDED FABRIC FILTERWEAVE 404 FILTERWEAVE 404 FILTERWEAVE 404 MIRAFI 180N ARMORED EROSION CONTROL (3) Mild Current Exposure, Minimal Drawdown Potential, Non-Vegetated Wave Exposure, High Velocity Channel Lining, Spillway Overtopping Soil Retention (1) Permeability Clogging Resistance Flow Conditions RECOMMENDED FABRIC Soil Retention (1) Permeability Clogging Resistance Flow Conditions RECOMMENDED FABRIC 12.5 mm 1.5 mm 0.7 mm 0.55 mm 5 x x x x 10-5 P.O.A. > 6% P.O.A. > 6% P.O.A. > 6% P.O.A. > 6% Mild Currents Mild Currents Mild Currents Mild Currents FILTERWEAVE 400 FILTERWEAVE 400 FILTERWEAVE 400 FILTERWEAVE mm 0.60 mm 0.28 mm 0.22 mm.5 x x x x 10-4 P.O.A. > 6% P.O.A. > 6% P.O.A. > 6% P.O.A. > 6% Severe Wave Attack Severe Wave Attack Severe Wave Attack Severe Wave Attack FILTERWEAVE 404 FILTERWEAVE 404 FILTERWEAVE 500 FILTERWEAVE Maximum opening size of geotextile (O 95 ) to retain soil. 2 Steady state flow condition. 3 Dynamic Flow Conditions

21 Clayey Sand (SC) k s =.00001cm/s PI = 16.0 C c = 20 C' u = n/a d' 50 = n/a C u = 345 d 50 =.55mm d 90 = 5.8mm > 10% silt < 20% clay.21 mm 1 x 10-5 n > 30% Sandy Silt (ML) k s =.00005cm/s PI = 0 C c = 2.9 C' u = 1.7 d' 50 =.07 C u = 10.8 d 50 =.072mm d 90 =.13mm.24 mm 5 x 10-5 n > 30% Lean Clay (CL) k s = cm/s PI = 16.7 C c = 3.3 C' u = n/a d' 50 = n/a C u = 36 d 50 =.014mm d 90 =.05mm > 16% silt < 20% clay.21 mm 1 x 10-7 n > 30% DISCLAIMER The information presented herein will not apply to every installation. Applicability of products will vary as a result of site conditions and installation procedures. Final determination of the suitability of any information or material for the use contemplated, of its manner of use, and whether the use infringes any patents, is the sole responsibility of the user. Mirafi is a registered trademark of Nicolon Corporation. DRAINAGE PAVEMENT GEOTEXTILE FILTER FABRIC TYPICAL SECTIONS AND APPLICATIONS: AGGREGATE PERFORATED PIPE Seepage Cut-off Pavement Edge Drains Slope Seepage Cut-off Surface Water Recharge Trench or "French" Drains LOW Non-dispersive MIRAFI 140N Series.21 mm LOW Uniformly Graded Dense MIRAFI 140N Series.18 mm LOW Non-dispersive MIRAFI 140N Series.21 mm Compacted Native Soil Geogrid Surcharge Compacted Drainage Fill Geotextile Filter Fabric 6 Minimum Granular fill Structure Pressure Relief Foundation Wall Drains Retaining Wall Drains Bridge Abutment Drains Planter Drains 1 x 10-5 n > 30% HIGH Non-dispersive 5 x 10-5 n > 30% HIGH Uniformly Graded Medium 1 x 10-7 n > 30% HIGH Non-dispersive NONWOVEN GEOTEXTILE DRAINAGE LAYER LINER GEOTEXTILE FILTER FABRIC Leachate Collection and Removal Blanket Drains Subsurface Gas Collection MIRAFI 160N MIRAFI 180N MIRAFI 160N ARMORED EROSION CONTROL 1.4 mm 1 x 10-5 P.O.A. > 6% Mild Currents 0.13 mm 5 x 10-5 n > 30% Mild Currents mm 1 x 10-7 n > 30% Mild Currents ROCK REVETMENT GEOTEXTILE FILTER FABRIC River and Streambed Lining Culvert Inlet and Discharge Aprons Abutment Scour Protection Access Ramps FILTERWEAVE 400 MIRAFI 1100N MIRAFI 1160N Proper installation of filtration geotextiles includes anchoring the geotextile in key trenches at the top and bottom of 0.55 mm 1 x 10-4 P.O.A. > 6% Severe Wave Attack 0.07 mm 5 x 10-4 P.O.A. > 6% Severe Wave Attack mm 1 x 10-6 n > 30% Severe Wave Attack GEOTEXTILE F Coastal Slope Protection Shoreline Slope Protection Pier Scour Protection Sand Dune Protection FILTERWEAVE 404 MIRAFI 1160N MIRAFI 1160N Underwater geotextile placement is common and must include anchorage of the toe to resist scour.

22 For more information on Mirafi Geotextiles Filters in drainge and armored erosion control applications, contact one of the following offices: In North America contact: Ten Cate Nicolon 365 South Holland Drive Pendergrass, Ga Toll free: Fax: log on to our website: In Europe contact: Ten Cate Nicolon Europe Sluiskade NZ 14 Postbus AE Almelo The Netherlands Tel: Fax: In Asia contact: Royal Ten Cate Regional Office 11th Floor, Menara Glomac Kelana Business Centre 97, Jalan SS 7/ Petaling Jaya Selangor Darul Ehsan Malaysia Tel: Fax: In Latin America & Caribbean contact: Ten Cate Nicolon 5800 Monroe Road Charlotte North Carolina USA Tel: Fax:

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35 Mirafi 160N Mirafi 160N is a needlepunched nonwoven geotextile composed of polypropylene fibers, which are formed into a stable network such that the fibers retain their relative position. Mirafi 160N geotextile is inert to biological degradation and resists naturally encountered chemicals, alkalis, and acids. Mirafi 160N meets Aashto M Class 2. Mechanical Properties Test Method Unit Minimum Average Roll Value MD CD Grab Tensile Strength ASTM D 4632 N (lbs) 712 (160) 712 (160) Grab Tensile Elongation ASTM D 4632 % Trapezoid Tear Strength ASTM D 4533 N (lbs) 267 (60) 267 (60) CBR Puncture Strength ASTM D 6241 N (lbs) 1780 (400) Apparent Opening Size (AOS) 1 ASTM D 4751 mm (U.S. Sieve) (70) Permittivity ASTM D 4491 sec Flow Rate ASTM D 4491 l/min/m 2 (gal/min/ft 2 ) 4481 (110) UV Resistance (at 500 hours) ASTM D 4355 % strength retained 70 1 ASTM D 4751: AOS is a Maximum Opening Diameter Value NTPEP No. GTX Physical Properties Test Method Unit Typical Value Weight ASTM D 5261 g/m 2 (oz/yd 2 ) 220 (6.5) Thickness ASTM D 5199 mm (mils) 1.7 (65) Roll Dimensions (width x length) -- m (ft) 4.5 x 91 (15 x 300) Roll Area -- m 2 (yd 2 ) 418 (500) Estimated Roll Weight -- kg (lb) 97 (215) Disclaimer: TenCate assumes no liability for the accuracy or completeness of this information or for the ultimate use by the purchaser. TenCate disclaims any and all express, implied, or statutory standards, warranties or guarantees, including without limitation any implied warranty as to merchantability or fitness for a particular purpose or arising from a course of dealing or usage of trade as to any equipment, materials, or information furnished herewith. This document should not be construed as engineering advice TenCate Geosynthetics North America Mirafi is a registered trademark of Nicolon Corporation FGS ETQR49