SECTION III

LEACHATE AND CONDENSATE MANAGEMENT PLAN

LEACHATE AND CONDENSATE MANAGEMENT PLAN

WAIMANALO GULCH SANITARY LANDFILL KAPOLEI, HAWAII

PREPARED BY

WASTE MANAGEMENT OF HAWAII, INC.

REVISED OCTOBER 2020

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TABLE OF CONTENTS

1.0 Introduction ............................................................................................................... 3 2.0 Condensate ............................................................................................................... 3 3.0 Leachate Generation ................................................................................................. 3 4.0 Leachate Collection and Removal System ................................................................ 4

4.1 Leachate Collection Sumps.................................................................................... 4 4.2 Leachate Maintenance Levels ................................................................................ 4

4.2.1 Leachate Sump Pump Systems ........................................................................ 5 4.2.2 Pump Settings .................................................................................................. 5

5.0 Leachate Storage & Disposal .................................................................................... 5 6.0 Leachate Monitoring and Sampling ........................................................................... 6

6.1 Responsibilities ...................................................................................................... 6 Figure Figure 1. Site Leachate Locations

Leachate Sump Diagrams

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ACRONYMS AND ABBREVIATIONS

amsl above mean sea level

BMP Best Management Practices

btoc below top of casing

DOH Department of Health, State of Hawaii

ft feet

GCCS Gas Collection and Control System

HAR Hawaii Administrative Rules

LCRS Leachate Collection and Removal System

LFG Landfill Gas

MSW Municipal Solid Waste

WGSL Waimanalo Gulch Sanitary Landfill

WMH Waste Management of Hawaii, Inc.

WWTP Waste Water Treatment Plant

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1.0 INTRODUCTION

Waste Management of Hawaii, Inc. (WMH), has prepared this Leachate and Condensate

Management Plan to establish the standard operating, maintenance, and disposal

procedures for leachate and condensate generated at the Waimanalo Gulch Sanitary Landfill

(WGSL).

This Leachate and Condensate Management Plan is part of the WGSL Site Operations

Manual and should be used as the primary document for leachate and condensate

management at the facility.

2.0 CONDENSATE

Landfill gas condensate is a liquid produced in landfill gas collection systems. The

condensate is removed as the landfill gas is withdrawn from the landfill. Condensate is

composed primarily of water and organic compounds. Condensate management is

accomplished by sloping the landfill gas (LFG) transmission piping to a low point in the

landfill gas collection and control system (GCCS) piping for collection of the condensate. The

condensate collection sump/drain is located at this low point, to collect the condensate and

remove it from the transmission piping. The condensate collection sump and knockout vessel

are located along the gas collection header at the flare station. These systems collect and

transport the condensate through the collection header to a 12,000-gallon storage tank. The

flare is designed to allow condensate from the tank to be injected into the flare. In the case

that the condensate cannot be injected into the flare, an outside contractor pumps the

condensate out of the storage tanks and into a mobile tanker truck. The condensate will likely

be mixed in the tanker truck with leachate from one of the existing on-site leachate tanks.

The leachate/condensate mixture is then transported to a City and County of Honolulu Waste

Water Treatment Plant (WWTP) for disposal.

3.0 LEACHATE GENERATION

Leachate is generated when water percolates through disposed refuse. This percolation can

occur when precipitation infiltrates directly into the waste, or when moisture in the refuse

(whether present when landfilled or generated after landfilling as a product of bio-

decomposition) filters or leaches out.

Leachate generation is minimized by using the following best management practices (BMPs)

at the WGSL:

• Maintaining positive drainage on top of the landfill to minimize infiltration. Storm

water runoff from covered areas of the landfill is directed to down drains/swales

that will carry the runoff to the stormwater detention basins. Precipitation that falls

on the active face is managed there and not directed off the landfill.

• Use of geosynthetic tarps in active filling areas. These tarps prevent rainfall and

storm water from infiltrating the waste cells and reduce the potential for erosion.

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• Maintaining surface water drainage around the perimeter of the landfill to prevent

surface water run-on into the active disposal area.

4.0 LEACHATE COLLECTION AND REMOVAL SYSTEM

All disposal areas (Ash and Municipal Solid Waste [MSW] cells) constructed at the WGSL

are equipped with a bottom and side slope composite liner and leachate collection and

removal system (LCRS) that meets Federal (Subtitle D equivalent) and State of Hawaii

Administrative Rules (HAR) 11-58.1-14 requirements. Subtitle D regulations require that

leachate not be allowed to accumulate on the landfill bottom liner to a depth of more than 30

centimeters (approximately 1 foot), not including that contained in collection sumps.

A description of the liner systems that are in place at the WGSL are detailed in Section II

WGSL Operations Plan of this Site Operations Manual.

4.1 LEACHATE COLLECTION SUMPS

There are five leachate collection sumps at the WGSL

• Ash Sump, collects leachate from ash monofill cells 1 through 8;

• MSW Cell 4B sump, collects leachate from MSW cells 5 through 11

• MSW Cell E1 Sump, collects leachate from MSW cells E1through E4;

• MSW Cell E6 sump, collects leachate from ash monofill cells E5, E6 and E7; and

• Ash Cell E8 sump, collects leachate from ash monofill cells E8 and E9.

See the attached Figure for leachate sump locations.

4.2 LEACHATE MAINTENANCE LEVELS

See table below for each leachate sump compliance elevation.

Leachate Sump Compliance Elevation

(ft amsl)

Bubbler Reading

(inches)

Manual Measurement

(ft btoc)

Ash Sump 88.1 83.1 74.96

MSW Cell E1 227.1 43.75 68.39

MSW Cell 4B 124.9 42 122.52

Ash Cell E8 520.18 48.4 261.00

MSW Cell E6 389.6 48.4 193.48

ft Feet amsl Above mean sea level btoc Below top of casing

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4.2.1 Leachate Sump Pump Systems

The leachate sump pump systems consist of automatic pumps, flow meters, pressure

transducers (except for Ash Sump), and bubbler systems. The instrumentation automatically

starts, stops, and modulates pump speeds to efficiently and reliably pump variable flow rates.

The pump systems utilize electric submersible leachate pumps, a submersible electronic

pressure transducer, and a bubbler system. The pressure transducer and the bubbler system

are used to monitor the leachate levels (in inches) in the sumps. The pressure transducer

provides the primary level control while the bubbler is a backup/secondary system.

The pump controls are configured to pump the leachate level down to as close to the riser

base plate as possible without causing air intrusion into the pump. The pumping systems

automatically maintain a specified flow rate based on the leachate levels in the sumps up to

the maximum capacity of the pump. Each leachate pump system can display alarms and

shutdowns, which are indicated by a red flashing light located on top of the control panel

enclosure. Electrical power is supplied to each system by Hawaiian Electric Company.

4.2.2 Pump Settings

With the pump selector switch in the “automatic” position, the leachate level in the sump will

rise until it reaches the user specified “pump on” level, which will start the pump. The pump

will then continue to run until the user specified “pump off” level has been reached. Pump

flow rates are also specified by the user. Pump level settings are set to maintain less than

one foot of head on the liner system.

At sumps Ash, E1, E6, and E8, the status of the pump system is indicated by lights (green,

amber, red) located on top of control panel. If the pump is running the green light indicator

will blink. If the leachate level in the sump rises above the pump start point, but is below the

user specified high level, the amber warning light will blink, indicating a pump or flow

problem. If the level further rises to a point above the user specified high-level alarm, the red

alarm light will blink, indicating an alarm or fault condition.

Manual operation at a user specified flow rate can also be started at any time by placing the

pump selector switch in the “hand” position. An outside electrical contractor handles repairs

or maintenance activities that need to be performed on the leachate pump systems or

associated equipment.

5.0 LEACHATE STORAGE & DISPOSAL

Leachate that is pumped out of the riser sumps is temporarily stored on-site in 20,000-gallon

steel frac tanks. There are currently five (5) 20,000-gallon steel frac tanks on-site. Three of

the frac tanks are located on the MSW 4B cell, and are attached to the E1 leachate sump,

the 4B sump, and the Ash sump. These three leachate storage tanks are situated within the

limits of the landfill waste footprint (lined area), which, in the event of a spill or release,

provides secondary containment. The other two leachate storage tanks are attached to sump

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E6 and the Ash E8 sump and are maintained with lined secondary containment basins.

These tanks are proposed to be moved to a bermed area on the MSW 4B cell that is situated

within the landfill footprint.

An outside contractor pumps the leachate out of the storage frac tanks and into a mobile

tanker truck. The leachate is then transported to a City and County of Honolulu WWTP for

disposal. The contractor measures and records the quantity (gallons) of leachate pumped out

of the storage tanks and hauled off-site for disposal. These quantities are maintained as part

of the sites operating record. Pumping the leachate directly to the sewer system for disposal

is being proposed.

6.0 LEACHATE MONITORING AND SAMPLING

The leachate riser pump systems are monitored weekly. The leachate data is recorded on

the monthly Leachate Logs for each sump. Data collected includes the level of leachate in

the sum, volume of leachate in each tank, and any comments or observations noted.

Annually a third-party consultant conducts leachate sampling activities in conjunction with the

site’s groundwater monitoring program. WGSL groundwater and leachate monitoring

activities are conducted pursuant to the WGSL Groundwater and Leachate Monitoring Plan

(Geosyntec, 2016) located in Section VII of this Site Operations Manual.

6.1 RESPONSIBILITIES

WGSL Site Manager has overall responsibility for implementation of this Plan and all

operational activities related to leachate management. The Site Manager manages and

interfaces with outside contractors and treatment facilities, schedules the necessary tank

trucks required to manage leachate, and ensures that observed deficiencies are corrected

and documented in a timely manner.

Waste Management Environmental Professional works with the Site Manager to ensure that

leachate levels in the sumps are maintained and kept in compliance with permit and

regulatory requirements. They coordinate the annual sampling and analytical testing of

leachate and ensures that the required reports are submitted to the Hawaii Department of

Health (DOH) and leachate treatment facilities (when necessary). The Environmental

Professional is the point of contact for regulatory agencies and handles permit compliance

issues and notifications to the DOH, as necessary.

FIGURE

E9E8

MSWCELL 10

MSWCELL 11

MSW

MSWMSW

MSWMSW

MSWMSWMSWASH ASH

ASHASH

ASHASH

ASH

ASHCELL 8CELL 7CELL 6CELL 5

CELL 4BCELL 4A

CELL 3CELL 2

CELL 1

CELL 8

CELL 7CELL 6 CELL 5

CELL 4CELL 3

CELL 2CELL 1

E2E1

E5

E7

MSW

MSW

CELL 4C

E3

MSWCELL 9

E4

E6

SITE ENTRANCE

ADMINISTRATION BUILDING

DETENTIONPOND

CONCRETE-LINEDDRAINAGE CHANNEL

ASH SUMP

SCALEHOUSEAND SCALES

LANDFILLGAS FLARE CELL 4B SUMP

CELL E1 SUMP

LEACHATE STORAGE TANKS(FOR E1, 4B, ASH SUMPS)

PERIMETER ACCESS ROAD

PROPERTY BOUNDARY

PERMITTED LIMITOF LANDFILL

MAINTENANCE AREA

LEACHATE STORAGE TANK(FOR ASH E8 SUMP)

LEACHATE STORAGE TANK(FOR E6 SUMP)

CELL E6 SUMP

CELLS E5/E6/E7/E8/E9ARE CURRENTLY PARTIALLYCONSTRUCTED.

ASH E8 SUMP

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Figure 1 - Site Leachate LocationsLeachate Management Plan

Waimanalo Gulch Sanitary Landfill Kapolei, O'ahu, Hawai'i

EXISTING GROUND ELEVATION (10-FT CONTOUR)

PROPERTY BOUNDARY

CELL BOUNDARY

LEGEND

LEACHATE SUMP DIAGRAMS

ASH LEACHATE SUMP / RISER

WAIMANALO GULCH SANITARY LANDFILL

TOP OF RISER ELEVATION: 163.06’ AMSL

LINER ELEVATION @ TOP OF SUMP: 87.1’ AMSL

GROUND SURFACE ELEVATION: 160.00’ AMSL

BOTTOM OF SUMP ELEVATION: 80.8’ AMSL

REINFORCED CONCRETE

NOT TO SCALE

Compliance Elevation 88.1’ ft amsl

4B LEACHATE SUMP/RISER

WAIMANALO GULCH SANITARY LANDFILL

DATE:

8/17/2017

FILENAME:

SITE1007.DWG

PROJ. No.•

W A S T E M A N A G E M E N T

TOP OF SUMP ELEVATION: 123.9 FT AMSL

TOP OF RISER ELEVATION: 247.41 FT AMSL

GROUND SURFACE ELEVATION: 246.3 FT AMSL

BOTTOM OF SUMP ELEVATION: 120.9 FT AMSL

COMPLIANCE ELEVATION: 124.9 FT AMSL

TOPOFRISERELEVATION:258.86 FT AMSL

GROUNDSURFACEELEVATION:255.7 FT AMSL

LINERELEVATIONATTOPOFSUMP:226.1 FT AMSL

E 1 LEACHATE SUMP/ RISER

WAIMANALO GULCH SANITARY LANDFILL

'\ SUMP BASEELEVATION:223.1FT AMSL

NOTTOSCALE

DATE::

8/17/2017

eW A ST E M A N A G E M E N T

FILENAME:

SITE1007.DWG

PROJ. No.

Compliance Elevation 227.1’ amsl

TOPOFRISERELEVATION:496.40 FT AMSL

GROUNDSURFACEELEVATION:491 FT AMSL

LINERELEVATIONATTOPOFSUMP: 388.6 FT AMSL

E 6 LEACHATE SUMP/ RISER

WAIMANALO GULCH SANITARY LANDFILL

'\ SUMP BASEELEVATION:384.90 FT AMSL

NOTTOSCALE

DATE::

8/17/2017

eW A ST E M A N A G E M E N T

FILENAME:

SITE1007.DWG

PROJ. No.

Compliance Elevation 389.6 FT AMSL

LINERELEVATIONATTOPOFSUMP: 519.18 FT AMSL

E 8 LEACHATE SUMP/ RISER

WAIMANALO GULCH SANITARY LANDFILL

'\ SUMP BASEELEVATION:515.18 FT AMSL

NOTTOSCALE

DATE::

03/2020

eW A ST E M A N A G E M E N T

FILENAME:

SITE1007.DWG

PROJ. No.

Compliance Elevation

520.18 FT AMSL

BENCH ELEVATION:

655.2 FT AMSL

TOPOFRISERELEVATION:

658.06 FT AMSL