Wastewater

Waikapu Country Town Development Master Plan

• Sewer system master plan 

Wastewater Considerations

General

• Allocation: 25 gallons per person, 1,900 persons

• The New Central Maui Wastewater Plant is scheduled to be completed in 2029, and commissioning will be done in early 2030.

  • SLH 2022 HB1600 FY 22-23, $3.5M + $20M

  • PLANS, DESIGN, CONSTRUCTION, AND EQUIPMENT FOR A CENTRAL MAUI WASTE WATER TREATMENT PLANT; PLANS MAY INCLUDE IMPROVEMENTS, RENOVATION, REFURBISHMENT, OR NEW CONSTRUCTION; GROUNDS AND SITE IMPROVEMENTS; EQUIPMENT AND APPURTENANCES; PROVIDED THAT PARTIAL MATCHING FUNDS BE PROVIDED BY THE COUNTY OF MAUI. 

  • Scheduled to open in 2031?

  • Ph1 housings have reserved 100k gallons per day capacity at Kahului Wastewater Plant, but it does not include the capacity for the new school. There is no additional capacity at Kahului WWP.

• DOH

  • Wastewater Management Plan Permit

  • Underground Injection Control (UIC) Permit

  • Use of Recycled Water for Irrigation Permit

• EPA

  • On-site wastewater system manual 

Temporary Capacity at Kahului WWTP (Plan B)

• Connect to 

• Requested 10,000 GPD temporary capacity at Kahului WWTP (1/31/25)

On-site Recycling (Plan C)

• Infiltrator 

• Estimate from Epic Cleantec

  • Epic Cleantec can handle the design & permitting (subcontract electrical)

  • Type: Blackwater

  • System Size: Max 25 gallons per person x 1,200 persons = 30k Gallons per day (previous estimate was 21,000 GPD)

  • System footprint: 1,500 sqft

  • System cost: $686k (tanks and piping are excluded) => Total $1.7M?

  • O&M: $100k/year by an outside contractor => Potential saving Ph1 $15k/year, Ph2 $30-k/year, $50-70k additional  cost per year. A school custodian can do O&M, but a level-2 wastewater operator is required for some operations. Estimate

    • Organic: breaks down with microbes, about 1% of the flow to be extracted for microbe management, every other week howl dry cake.

    • Non-organic: Metal, plastic, etc. are extracted before  processing and damped into general trash

    • Chemicals: Laboratory testing fee

  • Septic tanks with lower recycling % will lower the O&M, enough land space, but fields are at the high point and require additional  water pumps to operate

  • Require energy to process

  • Intermittent wastewater flow during school breaks: additional micro-feed to be added with additional expense

• Grant

  • Water SMART , Closing 1/14/25

  • HIEFC grant opportunities 

  • DOI Addressing Drought 

Temporary Septic Tank (Plan D)

Time the Phase I completion with the new WWP (Plan A)

Temporary Holding Tank (Plan D)

• DOH is stringent about installing a holding tank and keeping unprocessed black water for more than 24 hours. Obtaining the permit from DOH may be challenging.

• Install temporary wastewater holding tanks until the new central Maui wastewater plant becomes operational.

• Upon review I recommend NOT constructing a package plant. There are a number of reasons this could be problematic: estimating flows, the fluctuating nature of occupancy (weekends/holidays) and the general capex and maintenance costs etc. I would recommend using a temporary holding tank and budgeting for scheduled pumping/offhaul using a service like Valley Isle Pumping. - Zoltan (Mana Water)

Consulting

• Roth Ecological Design

• Mana Water

Temporary Connection to Kahului WWTP

Overview

To hedge the risk of delay in the completion of the new Central Maui WWTP, SFA is seeking temporary capacity at the Kahului WWTP to facilitate efficient wastewater management during the initial phase of the project.

Proposed Connection Plan

• Upon approval of temporary capacity at Kahului WWTP, SFA will implement the following:

• Connect the wastewater piping from the school (near the lowest point of phase I) to the proposed WCT lift station.

• The current WCT lift station location is at a higher elevation than some Phase I buildings, necessitating an additional lift pump to manage the elevation difference.

Alternative Solution

• To optimize infrastructure and reduce costs, SFA proposes relocating the WCT lift station to the intersection of Olohe and Waiale. Benefits of this approach include:

• Elimination of temporary piping and the additional lift pump.

• SFA will offset the relocation costs by funding the move of the temporary lift station further east.

Next Steps

• Await approval for temporary capacity at Kahului WWTP.

• Evaluate the feasibility of relocating the WCT lift station based on cost, timeline, and stakeholder input.

• Coordinate with relevant parties to finalize the connection or relocation plan.

Tracking

1/14/25 Darren, The SFA is asking us to follow up on a proposed condition in their Educational Contribution Agreement with WCT.  Attached is a sheet with language clouded that we have a question about.   It seems that there are multiple parameters being discussed.   It seems that 1,250 gallons per acre per day of stormwater drainage capacity is low for a site in Waikapu. Please share your thoughts on this proposed condition. - Kirk

5/19/25 Darren:

The SFA has asked our firm to preliminarily lay out proposed onsite infrastructure for the 26.2 acre campus.May we request AutoCAD drawing files of your civil infrastructure plans on Olohe Street, Puapualenalena Place and the school's frontage portion of Waiale Drive including:

1. Potable Waterlines

2. Non-Potable Waterlines

3. R-1 Waterlines

4. Drainlines

5. Sewerlines

Kirk

5/19/25 Darren: Sorry, but we have one more question regarding fire protection for WCT. Which system supplies water for onsite and offsite fire protection needs for WCT? - Kirk

5/19/25 ATTACHMENT A to this message is an AutoCAD .dwg file containing our linework for the streets fronting the School Site and their utilities. ATTACHMENTS B and C are construction plans for both Waikapu Country Town’s Initial Backbone Infrastructure deployment and Waiale Road Extension adjacent to the School, should you need to refer to them. Regarding your last question, fire protection is provided by the potable water system. - Darren

9/24/25 Darren, 

We understand that a temporary 6" sewer force main is proposed to convey wastewater from the Waikapu WWPS (Interim Sewer Lift Station) to connect to the existing 4" sewer force main crossing under Waikapu Stream. 

We anticipate an average wastewater flow from Phase 1 of Waikapu School to be approximately 7,250 GPD. 

HISFA has requested that we consult your firm as to the adequacy of the new 6" force main and existing 4" force main stream crossing including our anticipated wastewater flow from the school. - Kirk