APPX F_MEMO LANDFILL OPTION COST ESTIMATES 051809.DOC 1 

MEMORANDUM

Planning-Level Cost Estimates for Landfill Options 

TO: Mike Dworsky, County of Hawai`i 

COPIES: Mark Dexter, HNL 

FROM: Dan Pitzler 

Cory Hinds 

DATE: March 27, 2009 

This memorandum provides background for planning-level cost estimates of two landfill 

options: 1) transfer waste from East Hawai`i to the West Hawai`i Sanitary Landfill (WHSL) 

and 2) expanding the South Hilo Sanitary Landfill (SHSL) in two phases, with the first phase 

consisting of a 7-acre lateral expansion of the existing landfill, and the second phase 

consisting of expanding the landfill into quarries adjacent to the SHSL site. It is intended to 

outline the rationale and assumptions for each option and assist the County in decision 

making about long-term disposal options. 

The cost estimates are shown on a per-ton basis for managing the waste currently disposed 

of at the County’s SHSL. An analysis of the County’s budget resulted in an estimated perton cost of landfilling at the SHSL of $57.64 per ton in 2007-08. The estimated per-ton 

disposal cost of each landfill option follows, with a high-low cost range shown for the new 

landfill development options. 

 Per-ton Cost (2009$) 

Landfill Options Low High

Transfer waste from East Hawai`i to the WHSL $82 

7-acre lateral expansion of SHSL $82 $94 

Expand SHSL into Quarries $69 $73 

1. Transfer Waste from East Hawai`i to the WHSL 

As shown in Exhibit 1, the estimated cost of transferring waste from East Hawai`i for 

disposal at the WHSL is $82 per ton. 

EXHIBIT 1 

Cost Summary – Transfer Waste from East 

Hawai`i to the WHSL 

Cost Element 

2009 

Dollars 

per ton 

 Transfer Station Operations $11.00 

 Transportation $24.00 

 Landfill Cost $47.00 

 Total $82.00 
PLANNING-LEVEL COST ESTIMATES FOR LANDFILL OPTIONS 

APPX F_MEMO LANDFILL OPTION COST ESTIMATES 051809.DOC 2 

For comparison, Table 3.2 of the 2004 Sort Station EIS1 estimated the per-ton cost of transfer, 

transport, and disposal at $7.21, $18.83 and $34.83, respectively, for a per-ton total of $58.86. 

Escalating those costs from 2003 to 2008 using Engineering News Record’s Construction 

Cost Index, would increase that estimate by 29 percent to $75.93 per ton, or about 7 percent 

less than the estimate shown in Exhibit 1. 

Planning-level operating costs for a transfer operation at the SHSL Sort Station are 

presented in Exhibit 2. These costs include an estimate of the labor (FTEs) and equipment 

necessary to operate the station. 

The estimated cost of transporting waste from the Sort Station to the WHSL is shown in 

Exhibit 3. These estimates are based on a trucking cost model used by CH2M HILL on 

recent similar projects, with input parameters adjusted to reflect specific conditions that 

apply in Hawai`i County. The estimate also includes an adjustment to account for the 

assumption that waste would be hauled directly from the Pahoa Recycling and Transfer 

Station to the WHSL instead of to the SHSL for transfer; this cost adjustment is based on the 

County’s 2007-08 actual per-mile trucking cost. Exhibit 4 presents the assumptions used to 

estimate the number of tractor trailers needed for the trucking operation. 

The estimated variable per-ton cost for landfilling at the WHSL is calculated based on actual 

2007-08 costs as shown in Exhibit 5. It was assumed that no additional County staff would 

be needed at the WHSL to accommodate the increase in waste from East Hawai`i. Should 

additional workers be required, the unit costs would be higher than shown. 

Other cost considerations relevant to this option that are not included in these cost estimates 

include: 

• No costs have been included for environmental review, transportation improvements or 

mitigation. Depending on the transportation route selected from the Sort Station to the 

WHSL, and the number and types of permits and studies required, it’s possible that 

additional costs would be incurred to address these considerations. 

• Landfilling waste from East Hawai`i at the WHSL will shorten the life of that landfill. 

Long-term disposal forecasts (that take into account population and employment 

growth and the effect of planned diversion programs) are that the WHSL has an 

additional 38 years of capacity remaining2. If waste from East Hawai`i is added starting 

in 2013-14 (the time when the SHSL is likely to close if it is not expanded), the WHSL’s 

capacity would be exhausted in 27 years, or 11 years sooner. 

 

1 County of Hawai`i. 2004. Final Environmental Impact Statement, Construction and Operation of the East Hawai`i Regional 

Sort Station.

2 The County is currently investigating options to extend the years of remaining capacity at the WSHL. These options would be 

evaluated as part of the WHSL master plan proposed for implementation as part of this ISWMP Update. 
PLANNING-LEVEL COST ESTIMATES FOR LANDFILL OPTIONS 

APPX F_MEMO LANDFILL OPTION COST ESTIMATES 051809.DOC 3 

EXHIBIT 2 

Transfer Station Operating Cost 

 Notes 

Typical Annual Tonnage 80,000 

TS Operating hours 

 per year 3,801 10.5 hours per day 

 per week 73 

Days per year 362 

tons per day 221 Annual tons / 362 

Peak hour tons 44 Conceptual "rule of thumb" - 20 percent in 

peak hour 

Peak hour trailers 2 Assumes 18 tons per trailer 

Blended Labor rate 

 Site attendants $49,885 2008-09 cost times 36 percent benefits 

(percent estimated from actuals) 

 Equipment operator $62,206 2008-09 cost times 36 percent benefits 

(percent estimated from actuals) 

Staffing CH2M HILL Estimates 

 Trailer Shuttle 1 $62,206 $62,206 

 Dozer 1 $62,206 $62,206 

 Site attendant at main building 2 $49,885 $99,770 

 Scale attendant 1 $62,206 $62,206 

 Extra FTE for illness/vacation 0.4 $22,030 

 Total Staff 5.4 $308,419 

 Multiplier for >40 hours per wk 1.8 

 Total FTEs 10.0 $563,606 

 

Annual staffing $563,606 

Non-labor percent 60 

percent CH2M HILL estimate for this type of facility 

Non-labor cost $338,163 Equipment replacement and operations, fuel, 

insurance, utilities, general site maintenance 

 Total $900,000 

 $/ton disposed $11.25 Total / tons per year 

Staff per operating hour 5.5 Avg number of staff on-site at one time 
PLANNING-LEVEL COST ESTIMATES FOR LANDFILL OPTIONS 

APPX F_MEMO LANDFILL OPTION COST ESTIMATES 051809.DOC 4 

EXHIBIT 3 

Trucking Cost Estimate 

Operating Assumptions Equipment Cost 

Origin Location SHSL Tractor (truck) Make and Model County 

Actuals 

Destination WHSL Number of Tractors in the Fleet 7.0 

Miles (one way) 77.5 Annual Lease $24,000 

Average Miles per Hour 40 Total Tractor Cost $168,000 

Workdays per Week 7 

Annual Workdays 362 Trailer Make and Model Tri-axle Trailer 

Monthly Tons through the T/S 6,682 Number of Trailers in the Fleet 14 

Annual Trips 4,455 Annual Lease $11,000 

Average Tons per Trip 18 Total Trailer Financed Cost $154,000 

Compacted / Uncompacted Loads Uncompacted 

Average Loading Time 20 Total Tractor and Trailer Lease $322,000 

Average Unloading Time 20 

Average Roundtrip Time 3.88 Required Tractor Quantity 7.0 

Total Time per Trip 4.54 Required Trailer Quantity 14 

Loads per day 12 

 Licenses & Taxes 

Labor Assumptions State Highway Use Tax n.a. 

 Non-driving percent 0 percent State Hawai`i 

 Driver hours per day 56 Rate per mile n.a. 

 Hostler hours per day 0 State An. Registration (per truck) n.a. 

 Total hours per day 56 

 Driver Annual Wage $45,740 Federal Hwy Use Tax (per truck) $550 

 Loaded Driver Percentage 36 percent Insurance (per truck per year) $1,000 

 Annual Insurance $7,000 

Fuel Cost 

Fuel MPG 5.0 Operational Assumptions 

Diesel Cost per Gallon $4.00 SG&A Overhead Percentage 0 percent 

 (SG&A is Sales / Mgmt / Admin / Dispatch) 

Repair & Maintenance Profit Margin Percentage 0 percent 

Truck Cost per Mile $0.30 Interest Rate 5.00 percent 

Trailer Cost per Mile $0.22 

Annual Cost 

per Truck 

Annual Trucking 

Costs Cost per Ton Cost per Mile 

Truck $24,000 $168,000 $2.10 $0.49 

Trailer $11,000 $154,000 $1.92 $0.45 

Labor $605,060 $7.55 $1.75 

Fuel $552,374 $6.89 $1.60 

R&M $359,043 $4.48 $1.04 

Insurance $14,000 $0.17 $0.04 

License & Fees $0 $0.00 $0.00 

G&A $0 $0.00 $0.00 

Profit $0 $0.00 $0.00 

Total $1,852,478 $23.10 $5.37 

Direct haul from Pahoa TS to WHSL $106,000 

Total tons 81,487 

Total per ton cost $24.03 
PLANNING-LEVEL COST ESTIMATES FOR LANDFILL OPTIONS 

APPX F_MEMO LANDFILL OPTION COST ESTIMATES 051809.DOC 5 

EXHIBIT 4 

Estimated Number of Tractors Needed to Haul to WHSL 

Origin Location SHSL 

Destination WHSL 

Miles (one way) 77.5 

Average speed (miles per hour) 40 

Workdays per week 7 

Annual workdays 362 

Monthly tons throughput 6,682 

Average tons per trip 18 

Compacted / Uncompacted Loads Uncompacted 

Average loading time (mins.) 20 

Average unloading time (mins.) 20 

Average roundtrip driving time 3.9 

Total time per trip (hrs.) 4.54 

Hrs per day of tractor operations 10 

Trips per truck/day 2.20 

 Spare 1.0 

No. of tractors needed per shift 6.6 

EXHIBIT 5 

Estimated Variable Landfilling Cost at the WHSL 

$ per ton 

Contract costs $42.97 

Contract escalation $0.97 

Fuel $1.59 

Parts $1.73 

Total variable cost $47.26 

2. SHSL Expansion 

The cost of expanding the South Hilo Sanitary Landfill is less certain than the cost of 

transporting waste to the WHSL. Thus discussion of this option is based upon certain 

assumptions regarding feasibility, and the cost estimates as presented have some degree of 

uncertainty. Additional analysis would be needed to further refine the cost estimates and 

confirm the feasibility of this option. 

Expansion of the SHSL could potentially be accomplished in two separate phases: first, a 

7-acre lateral expansion to the northwest; and second, a larger-scale expansion into rock 

quarries located adjacent to the southeast perimeter of the site. A discussion of the two 

possible expansion areas follows. 

Seven-Acre Lateral Expansion to the Northwest 

It is assumed that the initial expansion would occur on a 7-acre vacant land parcel which 

borders the SHSL to the northwest. It was initially assumed that expansion into this area 
PLANNING-LEVEL COST ESTIMATES FOR LANDFILL OPTIONS 

APPX F_MEMO LANDFILL OPTION COST ESTIMATES 051809.DOC 6 

would also allow the County to increase the elevation of a portion of the existing landfill, 

and an initial estimate of the capacity that would be added by this expansion is just less than 

2 million cubic yards3. At 2007-08 fill rates (about 250,000 cubic yards per year), this would 

have provided about 8 years of added capacity. However, the County recently received an 

unfavorable opinion from the Federal Aviation Administration that would limit the extent 

to which the SHSL could be expanded vertically. Thus, it is now anticipated that the lined 

expansion on this parcel would provide only an additional 4 years of capacity. 

State and federal regulations (Hawai’i Administrative Rules [HAR], Title 11, Chapter 58.1 

and 40 CFR 258.48) require that all new landfills be constructed with a waste containment 

system consisting of a bottom liner with leachate collection and recovery system. The liner 

system would consist of two layers of heavy duty plastic geomembrane, placed above and 

below a geosynthetic clay liner. The bottom of the new landfill cell would also have an 

engineered drainage layer. In addition, an expansion of the County’s existing groundwater 

monitoring program would probably be required. 

Estimated Capital Cost 

The estimated construction cost for the 7-acre lined cell is $3.2 million4. To this estimate 

must be added the cost of a leachate collection and treatment system, a landfill gas 

collection system, and added groundwater monitoring. In regions with high annual 

precipitation rates higher volumes of leachate are produced and must be managed. In 

response, Hawai`i County should consider taking steps to actively reduce the volume of 

leachate generated in the lined expansion by maintaining a system of plastic membranes 

and tarps to cover the waste. When the waste is covered by membranes or tarps, infiltration 

of precipitation can be mitigated and runoff can be managed as storm water. 

Even with the use of membrane and tarp covers, leachate will be generated that requires 

treatment. Leachate that collects on the landfill liner would be pumped out of the cell, and 

then treated prior to discharge. Treatment options include treatment at the local wastewater 

treatment plant (WWTP) near the Hilo Airport, and treatment using constructed wetlands. 

Treating leachate at the WWTP would be costly because it would involve either constructing 

a lengthy pipeline or trucking leachate to the WWTP. Further, the County wastewater 

division prefers that other options be considered for leachate treatment: thus, the County 

investigated the feasibility of wetlands treatment. An initial feasibility evaluation indicated 

that wetlands treatment could effectively treat the leachate5. Additional assessment has 

been completed since the initial evaluation, resulting in a range of cost estimates for the use 

of constructed wetlands for leachate treatment. Estimated costs for leachate treatment using 

constructed wetlands for leachate treatment for four scenarios are presented in Exhibit 6. 

 

3 "South Hilo Sanitary Landfill Proposed Expansion Feasibility and Capital Cost Estimate". 2008. SWT Engineers. 

4 ibid. plus 10 percent engineering and 8 percent permitting. 

5 CH2M HILL. 2008. South Hilo Sanitary Landfill Leachate Quality Improvement Using Treatment Wetlands – High Level 

Sizing and Cost Opinion. Technical Memorandum to SWT Engineering. 
PLANNING-LEVEL COST ESTIMATES FOR LANDFILL OPTIONS 

APPX F_MEMO LANDFILL OPTION COST ESTIMATES 051809.DOC 7 

 

EXHIBIT 6 

Estimated Capital Cost of Constructed Wetland Leachate Treatment at SHSL 

 

 

 Surface Flow Wetland 

Vertical Subsurface 

Flow Wetland 

Scenario 

Cover 

Scenario Fill Plan 

Design 

Flows 

Equalization 

Tank 

(gallons) 

Wetland 

Size 

(acres) 

Capital 

Cost 

Wetland 

Size 

(acres) 

Capital 

Cost 

1 

Aggressive: 

60 percent 

cover 

Three 15-

foot lifts 

Avg annual 

- 5.5 gpm 60,000 1.2 $1,610,000 0.2 $1,801,000 

2 

Moderate: 

35 percent 

cover 

Three 15-

foot lifts 

Avg annual 

- 8.9 gpm 60,000 1.5 $1,983,000 0.3 $1,956,000 

3 No cover One 15-

foot lift 

Avg annual 

- 13.5 gpm 60,000 2.3 $2,261,000 0.6 $2,398,000 

4 No cover One 15-

foot lift 

Peak 

monthly - 82 

gpm 

300,000 10 $6,677,000 1.8 $4,847,000 

Source: CH2M HILL, 2009. 

As shown in Exhibit 6, at this level of analysis there are a number of uncertainties about the 

sizing and cost of using constructed wetlands for leachate treatment. Wetland sizing 

depends on contaminant and hydraulic loading rates. Contaminant loading rates for the 

short-term expansion into the 7-acre parcel are unknown, but were assumed using a 

combination of data from "wet" landfills in Oregon and Alaska and existing data from a 

landfill on Oahu6. Based on data from a high-rainfall landfill in Unalaska, Alaska, 

contaminant loading rates were decreased by 50 percent during peak flows to account for 

dilution. The contaminant loading used in this analysis is likely to be conservative because 

actual dilution from rainfall at the SHSL may be higher. Because the exact data for 

contaminant loading is unknown, it is not certain at this stage whether smaller size wetlands 

would provide sufficient residence time for treatment. 

Hydraulic loading refers to the rate of leachate generation in the landfill liner. Leachate flow 

rate depends on liner area, climate inputs (e.g., rainfall and evaporation), cover used during 

operations to divert storm water, and thickness of in-place waste. The design flows for the 

scenarios shown in Exhibit 6 were estimated using the EPA HELP model7. Application of 

more membrane and tarps to divert storm water has the potential to decrease leachate 

generation and require a smaller wetland footprint for treatment. The most conservative 

estimate for wetland sizing and cost is Scenario 4 with no cover to divert storm water, a 

single 15-foot lift of waste in place over the entire cell, an equalization tank sized to 

accommodate the 10-year peak daily flow, and wetlands sized to accommodate peak 

monthly precipitation yielding a high leachate flow rate of 82 gpm. Less conservative 

 

6 County of Hawai`i. 2004. Final Environmental Impact Statement, Construction and Operation of the East Hawai`i Regional 

Sort Station. 

7 CH2M HILL. 2008. Estimate of Leachate Generation Rate for Proposed Lined Lateral Expansion of Hawai`i County’s Hilo 

Landfill. Technical Memorandum to SWT Engineering. 
PLANNING-LEVEL COST ESTIMATES FOR LANDFILL OPTIONS 

APPX F_MEMO LANDFILL OPTION COST ESTIMATES 051809.DOC 8 

scenarios assume more cover and the associated diversion of storm water, less generation of 

leachate, a smaller equalization tank, and smaller wetland sizing and the associated costs. 

Wetland sizing also depends on regulatory endpoints and compliance frequency. More 

stringent regulatory requirements typically require higher residence time in the treatment 

wetlands and larger size and cost. The wetlands treatment option assumes surface discharge 

of treated leachate and subsequent infiltration and migration to groundwater. Testing of 

treated effluent would be conducted to confirm regulatory requirements prior to discharge, 

and groundwater monitoring would be conducted to confirm that leachate discharge is not 

negatively impacting the shallow aquifer. 

For planning purposes it was assumed that leachate discharged from wetlands would 

contain lower concentrations of contaminants than are presently discharged in leachate 

infiltrating the subsurface from the existing unlined landfill. Leachate discharge regulatory 

criteria assumed for the current sizing are as follows: less than 200 milligrams per liter 

(mg/L) biological oxygen demand (BOD5), less than 25 mg/L total suspended solids (TSS), 

and less than 10 mg/L ammonia-nitrogen (NH4-N) and nitrate+nitrite- nitrogen (NOx-N). If 

actual regulatory endpoints are stricter than this, then required wetland size and cost would 

increase. Similarly, if monthly average compliance is permitted, then required size and cost 

would be smaller than if daily compliance is mandated. 

Potential additional steps to evaluate regulatory compliance issues, and how they affect 

wetland size and design would include the following: 

• Conduct a more thorough evaluation of contaminant loading for the potential lined 

expansions of the SHSL. 

• Conduct modeling of specific treatment wetland processes to select minimum size 

treatment area. 

• Meet with staff from the State of Hawai`i Department of Health Environmental 

Management Division, Clean Water Branch to evaluate regulatory requirements and 

discharge criteria for wetlands leachate treatment. 

The lined expansion would require a system to collect and manage landfill gas. The type of 

system, active or passive, would depend on the landfill gas system selected for the unlined 

portion of the landfill and a series of other factors. Thus, Exhibit 7 includes a passive control 

system as a low estimate, and an active control system as a high estimate. The estimate is 

only for the 7-acre expansion to the northwest of the existing landfill. 

Operations and Maintenance Costs 

In is anticipated that County staff levels for day-to-day operations would be similar to its 

current operations. O&M costs expected to increase include costs associated with diverting 

rainfall from waste, managing leachate, and additional monitoring and regulatory 

compliance. 

In Scenario 2 of Exhibit 6, it is assumed that capital costs to procure tarping, and labor costs 

for one extra FTE would be required. In Scenario 4, it is assumed that no extra effort would 

be made to divert rainfall from waste. 
PLANNING-LEVEL COST ESTIMATES FOR LANDFILL OPTIONS 

APPX F_MEMO LANDFILL OPTION COST ESTIMATES 051809.DOC 9 

Estimated additional annual costs for pumping leachate, groundwater monitoring, and a 

weekly walk through of the wetlands treatment system are $100,000 in Scenario 2 and 

$200,000 for Scenario 4. 

EXHIBIT 7 

Landfill Gas Cost Estimates 

 328,000 Tons from 7-acre expansion 

0.46 Tons per cubic meter 

 150,464 Cubic meters from 7-acre expansion 

0.00047 SCFM per cubic meter 

70.95901 SCFM 

 

Low - Passive System 

$0.31 $ per cubic meter (escalated for Hawai`i with 10 percent 

engineering) 

$47,000 Landfill gas cost for 7-acre expansion 

$4,700 Annual O&M (10 percent of capital) 

 

High - Active System 

Collection system 

$0.60 $ per cubic meter (escalated for Hawai`i with 10 percent 

engineering) 

$90,000 Landfill gas collection system cost for 7-acre expansion 

Flare system 

$600,000 $ per 1,000 scfm 

$123,000 Flare system capital cost for 7-acre expansion 

Total Active System 

$213,000 Sum of collection system and flare system costs 

$21,000 Annual O&M (10 percent of capital) 

Source: CH2M HILL, 2009. 

 

Periodic major maintenance of the wetland treatment system would be required, which 

could include replacing the equalization tank, reconstruction or cleanout of wetland cells, 

and/or development of a new infiltration basin. These costs are estimated to occur 

approximately every 6 years at a cost of $250,000 for Scenario 2 and about $900,000 for 

Scenario 4. 

Finally, it is estimated that three new monitoring wells would be constructed at a cost of 

$15,000 per well. Based on current County monitoring costs, it is assumed that it would cost 

an additional $7,500 per well annually, for a total of $22,500 per year in additional 

groundwater monitoring costs. 

Closure and Post-Closure Costs 

The SWT report (Table 3) estimates the added closure cost for the 7-acre extension of 

$1,156,000. Post-closure cost estimates are shown in Exhibit 8: the low estimate assumes 

passive landfill gas collection, and the high estimate assumes active landfill gas collection. 

When the extension is closed, it is assumed that any residual leachate would be treated 

along with leachate from the expansion into the quarries, with the costs included as part of 

that expansion. 
PLANNING-LEVEL COST ESTIMATES FOR LANDFILL OPTIONS 

APPX F_MEMO LANDFILL OPTION COST ESTIMATES 051809.DOC 10 

EXHIBIT 8 

Post-closure Cost Estimates for 7-Acre Expansion 

 Annual cost 

Item Qty Unit 

Unit 

cost Low High 

Inspections 7 acre $260 $2,000 $2,000 

Final cover 7 acre $1,300 $9,000 $9,000 

Surface water management 7 acre $1,300 $9,000 $9,000 

Vegetation 7 acre $390 $3,000 $3,000 

Gas management $5,000 $21,000 

Environmental monitoring 

 groundwater 3 wells $7,500 $23,000 $23,000 

 landfill gas 7 acre $780 $5,000 $5,000 

 leachate 7 acre $260 $2,000 $2,000 

 stormwater 7 acre $260 $2,000 $2,000 

Inspections 7 acre $260 $2,000 $2,000 

Total $55,000 $71,000 

Source: CH2M HILL, 2009. 

Per ton costs of 7-Acre Expansion 

A low and high range of per-ton costs for the 7-acre expansion is shown in Exhibit 9. As 

shown, the costs are expected to range from between $82 and $94 per ton for approximately 

4 years of added capacity. 

EXHIBIT 9 

Per-ton Costs of 7-Acre Expansion (2009$) 

 Low High 

Capital Costs (7-acre cell only) 

 Expansion - construction $3,200,160 $3,200,160 

 Leachate treatment system (wetlands) construction $1,956,000 $4,847,000 

 Landfill gas collection $47,000 $213,000 

Groundwater wells $45,000 $45,000 

 Closure $1,156,000 $1,156,000 

 Total Capital Cost $6,404,160 $9,461,160 

O&M Costs (7-acre cell only) 

 Landfill stormwater management $60,000 $0 

 Leachate O&M $100,000 $200,000 

 Leachate treatment upgrades (annual) $42,000 $103,000 

Added groundwater monitoring $23,000 $23,000 

 Annual post closure carea $277,000 $333,000 

 Total O&M Cost $502,000 $659,000 

Total capacity of expansion (tons) 328,000 328,000 

Added per ton costs 

 Capital $19.52 $28.85 

 O&M $6.12 $8.04 

 Total $25.65 $36.88 

Current (2007-08) per ton cost $56.74 $56.74 

Estimated per-ton cost of SH Lateral Expansion $82.39 $93.62 a

Assumes all funds are collected up front prior to closure and invested in a fund that is drawn down to 

zeor over a 30-year period (i.e., a sinking fund). 
PLANNING-LEVEL COST ESTIMATES FOR LANDFILL OPTIONS 

APPX F_MEMO LANDFILL OPTION COST ESTIMATES 051809.DOC 11 

The estimates assume that all funds for post-closure are collected up front in a sinking fund 

where the funds collect interest, and are then paid out during the 30-year post-closure 

period. While the County would probably fund post-closure differently, this approach is 

conservative. The costs shown are conservative because it is assumed that all costs would be 

spent at once, whereas the costs of post-closure (and the landfill gas system) would not be 

spent until the expansion is at capacity. In other words, the County could set aside a smaller 

sum into an interest-bearing account, and then spend them when needed. 

Expansion into the Quarries at the SHSL Site 

If constructed, the 7-acre expansion to the northwest of the current SHSL would provide 

capacity until approximately 2016-17. At that time, the County would need new landfill 

capacity for residuals from East Hawai`i. Hawai`i County owns several parcels of land 

currently used for quarry operations southeast of the existing landfill. The 75-acre quarry 

site is slightly larger than the existing landfill footprint. Preliminary estimates are that 

development of this quarry site for future landfill operations would provide 47 years of 

capacity beginning in 2017-18 when the 7-acre expansion is full8. 

This larger expansion area would be constructed and operated using the same assumptions 

noted above for the 7-acre northwest expansion (i.e., it assumes a liner system, constructed 

wetlands for leachate treatment, additional groundwater monitoring wells, an active landfill 

gas management, active stormwater management to minimize leachate production, and 

final closure and post-closure monitoring). 

It is assumed that the landfill would be operated as a series of 7-acre cells. When each cell is 

at capacity, it would be closed on an interim basis to minimize leachate generation. Thus, it 

is assumed that the constructed wetlands developed for the 7-acre northwest expansion 

would be of sufficient size to accommodate leachate generated from the larger expansion to 

the southeast. It is assumed that the existing groundwater monitoring network would 

provide adequate coverage in the downgradient direction from the quarry expansion area, 

and that new monitoring wells would be needed along the east and west perimeter and 

upgradient edges of the new cells. It is assumed that the landfill would eventually have an 

active landfill gas management system. Operations are assumed to be similar to what was 

assumed for Scenario 2 (Exhibit 6) for the 7-acre expansion (i.e., active steps would be taken 

to minimize leachate generation). 

It should be noted that no engineering analysis has yet been conducted for the quarry site. 

Thus, contingencies of 15 percent for the low estimate and 30 percent for the high estimate 

have been added to the capital costs to account for unknown conditions that could result in 

cost increases. In addition, expanding to the southeast into the quarry site would require a 

successful outcome of the State Land Use Boundary Amendment and County Zoning 

processes, completion of an Environmental Impact Statement, and resolution of Department 

of Health permitting issues. 

The estimated costs of landfilling in the quarry site are shown in Exhibit 10. 

 

8 This estimate accounts for growth in population and employment and assumes planned diversion programs in this ISWMP 

Update are implemented. The life of the landfill would increase if additional diversion programs are implemented in future 

ISWMP updates. 
PLANNING-LEVEL COST ESTIMATES FOR LANDFILL OPTIONS 

APPX F_MEMO LANDFILL OPTION COST ESTIMATES 051809.DOC 12 

EXHIBIT 10 

Per-ton Costs of Landfilling in Quarry Site (2009$) 

Capital Costs Low High 

 Expansion – construction $34,287,000 $34,287,000 

 Leachate treatment system expansion $450,000 $700,000 

 Landfill gas collection $11,212,000 $11,212,000 

Groundwater wells $135,000 $135,000 

 Closure $12,386,000 $12,386,000 

Add contingency (15 percent/30 percent) $6,825,000 $13,650,000 

 Total Capital Costa $65,362,000 $72,580,000 

O&M Costs 

 Landfill stormwater management $60,000 $0 

 Leachate O&M $100,000 $200,000 

 Leachate treatment upgrades (annual) $42,000 $103,000 

Added groundwater monitoringb $34,000 $34,000 

 Annual post closure carec

 $99,000 $99,000 

 Total O&M Cost $335,000 $436,000 

Total capacity of expansion (tons) 7,905,700 7,905,700 

Added per ton costs 

 Capital $8.27 $11.22 

 O&M $4.09 $5.32 

 Total $12.35 $16.54 

Current (2007-08) per ton cost $56.74 $56.74 

Estimated per-ton cost of SH Lateral Expansion $69.03 $73.28 

a

Costs would be spent over the life of the facility as new cells are opened; closure costs would be 

spent once the landfill is at capacity. 

b

Midpoint of annual costs over life of landfill as wells are progressively installed. 

c

Assumes all funds are collected up front prior to closure (sinking fund).