Published
Does the rock in your drainfield have to come from an approved source?
Not any gravel pit will do
The rock in a drainfield is not decoration — it is the distribution medium the whole permit is designed around, and Idaho treats where it comes from as part of the system. The state’s technical manual states the rule in one sentence:
“Aggregate and construction media must come from an approved source before installation in any subsurface sewage disposal system.”
— DEQ Technical Guidance Manual, December 2025, §3.2.8.1. Retrieved 5 October 2026
“Any subsurface sewage disposal system” is the operative phrase — standard trench or alternative, homeowner-built or installer-built, the source has to be on a list before a single load is ordered.
How a pit earns its way onto the list
Approval is a paperwork habit, renewed every year:
“To become an approved source, a supplier (typically a material pit or storage yard) must submit an annual sieve analysis for each source of drainfield aggregate or construction media that they would like to obtain approval of for installation in a standard or alternative subsurface sewage disposal system.”
— DEQ Technical Guidance Manual, December 2025, §3.2.8.1. Retrieved 5 October 2026
A sieve analysis is a lab shake-out of the material through standard sieves — proof of the sizing and cleanliness the rules demand. It goes to the local health district for review, and the districts keep the scoreboard:
“Each health district will maintain an approved source and materials list for their district and will provide a copy of this list to DEQ.”
— DEQ Technical Guidance Manual, December 2025, §3.2.8.1. Retrieved 5 October 2026
Four materials can appear on that list: drainfield aggregate (the drainrock itself), medium sand — the manual also calls it ASTM C-33 sand — pea gravel, and pit run material consisting of clean sand and gravel. Which material a given pit is approved for is listed pit by pit, not blanket-granted. What the rock itself must measure — sizes, cleanliness, and the barrier over it — is this site’s rock page.
EIPH’s list, June 2026
Eastern Idaho Public Health publishes its district list under a clear date — 6-26-2026 — with fourteen approved sources across its eight counties, from Rigby to Salmon to Challis. For a Fremont County build, the two rows that matter most are the closest ones, and they are also the most versatile:
| Source — location | Drainfield aggregate (drainrock) | Medium sand (ASTM C-33) |
|---|---|---|
| Parker’s Sand & Gravel — St Anthony | Yes | Yes |
| Siepert Crushing — St Anthony | Yes | Yes |
Both St Anthony sources are approved for both drainrock and medium sand — a combination only one other source on the list (Dahles Red E Mix, up in Salmon) matches. Every other entry is approved for one material or the other, not both. For sand-mound and pressurized designs that live on imported media, the alternative-system designs that consume medium sand are covered here.
Approval is not immunity
The list certifies the pit, not the load. EIPH’s own list prints the disclaimer the manual mandates:
“The Health District may still disapprove drainfield aggregate or construction media if it becomes contaminated during processing, loading, transport, storage or installation either at the source location or at a subsurface sewage disposal installation site.”
— Eastern Idaho Public Health, 2026 Drainfield Aggregate and Construction Media Approved List (dated 6-26-2026). Retrieved 5 October 2026
Mud in the truck bed, fines mixed in at the pit’s stockpile, aggregate stored on dirty ground at the job site — any of it can disqualify rock from an approved source. The responsibility is pinned to everyone who processes, provides, transports, stores or installs the material: the approved characteristics — size and cleanliness — have to survive all the way into the trench.
The list moves — check it before you order
The list’s own footer says so:
“This list will be updated as new sources or aggregate/media become approved.”
— Eastern Idaho Public Health, 2026 Drainfield Aggregate and Construction Media Approved List. Retrieved 5 October 2026
A pit whose annual sieve analysis lapses drops off; a new source can appear mid-season. The dated document is the answer, not last year’s memory of it.
Your half of the paperwork
- Before ordering, ask the installer which pit the rock comes from — then check it against the current EIPH list, material by material.
- Match the material to the system: drainrock for a standard trench, the listed medium for sand-based alternatives — approval does not transfer between them.
- Keep the delivery slips. The district’s homeowner guide requires DIY builders to document how many yards are used, and receipts for origin, quality and quantity are owed at inspection.
- If rock arrives looking dirty or fine-laden, stop the load — contamination on the way from an approved pit is still disqualifying.
- Confirm this season’s list with (208) 656-1467 before the truck rolls.
Common questions
Does drainfield rock have to come from an approved source?
Yes. Aggregate and construction media must come from an approved source before installation in any subsurface sewage disposal system - standard or alternative, no exceptions by build type.
How does a gravel pit become an approved source?
The supplier submits an annual sieve analysis for each source of drainfield aggregate or construction media to the local health district for review. Each district maintains the approved list for its territory and provides a copy to DEQ.
What materials appear on EIPH's approved list?
Four: drainfield aggregate (drainrock), medium sand - also called ASTM C-33 sand - pea gravel, and pit run material consisting of clean sand and gravel. Each source is approved per material, not across the board.
Which approved sources are closest to Fremont County?
Parker's Sand & Gravel and Siepert Crushing, both in St Anthony - and both are approved for drainrock and medium sand, a combination matched on EIPH's June 2026 list only by one source in Salmon.
Can rock from an approved source still be rejected?
Yes. The health district may still disapprove aggregate or media that becomes contaminated during processing, loading, transport, storage or installation - approval of the source does not certify any particular load.
How current is the approved list?
EIPH's list is dated - the current one 6-26-2026 - and it states it will be updated as new sources or materials become approved. Annual sieve analyses mean a source can also drop off, so check the dated list before ordering.