Curt Madsen, P.E. TRC Environmental Corporation Landfill Leachate Collection System Design CEE 427

Primary criteria…route leachate off liner to collection sump Designed to limit head to 12 inches or less Minimum base slope of 0.5% Maximum flow distance to collection pipe of 130 feet Minimum hydraulic conductivity of 1x10-2 cm/s of drainage layer aggregate Minimum 1-foot-thick select aggregate fill drainage layer 2 General (Referencing Wisconsin s. NR (5))

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Used to size pipes, pumps, tank storage volume, estimate treatment costs Based on NR (3)(a) and (b) – 6 inches/year for unclosed areas – 3 inches /year for intermediate covered areas – 1 inch/year for closed areas (with composite cover) Values above are more conservative than Help Model 4 Leachate Generation

Consists of select aggregate layer, collection piping, sumps, FM transfer pipes and cleanout access piping Select aggregate drainage layer placed on geotextile cushion (min 12 oz/yd) Aggregate is used to allow for future leachate recirculation Drainage layer consists of rounded to sub-angular (then use 16 oz/yd) stone with Unif. Coeff. < 4; max. particle diam. of 1.5 inches; a max. of 5% passes #4 sieve; no more than 5% passing #200 sieve Minimum pipe slope is 0.5% (typically greater) Collection piping placed in V-trenches (per NR (5)(d)) 5 Leachate Collection System

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Piping consists of 6-inch diameter perforated SDR 11 HDPE pipe Pipe strength calculations (attached) Perforated 0.5-inch holes, 2 rows set at 45 degrees and 6-inches Minimum of 6-inches of bedding material placed under pipe Minimum of 18-inches of bedding material placed over pipe Performed piping and permeability calculations to confirm required hydraulic conductivity without excessive migration of fines 7 Leachate Collection System (continued)

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Collection pipes extend to sump Perimeter cleanouts installed at both ends of pipe Lower portion of cleanout on side-slope may be perforated Leachate headwell 9 Leachate Collection System (continued)

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Leachate drains to collection sumps (fill with similar select aggregate) Sump volume sized to satisfy NR (5)(j) and accommodate sediment Inclined riser (18-inch-diameter SDR-17 HDPE) terminates into a vault Sump area must accommodate remedial installations Use back-flow preventer valves Submersible pumps / controlled with transducers / run-time meter 13 Leachate Removal and Storage System

Provide valves to isolate systems Pumps (place on PE skid plate) From vault leachate transferred to tank via forcemain (double cased) Minimum 4-day tank storage volume required (secondary containment) 14 Leachate Removal and Storage System (continued)

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Maximum “clean-out” length may not exceed 2,000 feet (NR (6)) Minimum 0.5% slope after accounting for primary and secondary settlement (100 yr) Similar bedding material requirements Utilize sweep bends (minimum radius of 10 pipe diameters) 19 Extended Length Leachate Collection Line Considerations

Questions? Curt Madsen, P.E. P: | E: