The Ultimate Guide to Hole Prep for Lockwood Precast Products

Cisterns • Septic Tanks • Egress Window Wells • Utility/Meter Vaults • Steps & More  

At Lockwood Precast in Billings, Montana, we’ve poured 5000 PSI concrete since 1963. From cisterns to septic tanks, egress wells to meter vaults, every piece is built to last generations—but only if the hole is prepped right. This one-stop guide covers some Lockwood Precast products with product-specific specs, common mistakes, and a print-ready checklist.

1. Start with the Lockwood Installation Drawing

Every item includes a job-specific drawing. It lists:

• Exact footprint

• Inlet and Outlet height (septic)

• Riser/Access locations

Lost it? Call (406) 245-4635—we’ll email you a new one.

2. Excavate with Product-Specific Over-Dig

Product	Over-Dig (Each Side)	Why It Matters
Cisterns	16"–18"	Leveling, backfill, pipe alignment, and lid sealing
Septic Tanks	16"–18"	Inlet/outlet stubs, riser access, and sealing
Egress Window Wells	24" minimum	Ladder clearance, leveling, drilling/anchoring, drainage pipe (if installing)
Utility/Meter Vaults	8"–12"	Conduit routing, water lines, and lid sealing
Steps & Small Vaults	8"	Bedding & compaction space

3. Gravel Base: Product-Specific Depths & Materials

Product	Min. Gravel Depth	Material	Key Purpose
Cisterns	3"–6" (3" min.)	¾" minus crushed	Cushion + micro-leveling
Septic Tanks	3"–6" (3" min.)	¾" minus crushed	Prevent floor cracks
Egress Wells	6"	¾" minus crushed	Drainage + frost heave buffer
Utility/Meter Vaults	6"	¾" minus crushed	Conduit bedding + stability
Steps	4"	¾" minus crushed	Level landing pad

Never use pea gravel—it shifts and settles. ¾" minus only.

4. Level Within ⅛" — Laser Every Time

• Laser level + 4-ft straightedge every 2 ft

• Max tolerance: ⅛" across entire base  

• Pro Hack: Crown center 1/16" high on tanks — weight settles it flat.

5. Boom Truck Access = Non-Negotiable

Our boom trucks with outriggers require:

• Firm, level ground within 6 ft of hole

• Clear access to the hole. No debris or dirt piled where the truck needs to be.

• 20 ft vertical clearance (no trees, power lines, eaves)

• Outrigger spread: 18–20 ft wide

• Flag/mark the drop zone before we arrive.

6. Final Hole Prep Checklist (All Products) Drawing reviewed — dimensions + gravel depth confirmed

 Over-dug per spec (16–18" for tanks, 12" for wells, 8" for vaults/steps)

 Gravel base installed & compacted (3–6" for cisterns/septic, 6" for wells/vaults, 4" for steps)

 Base level within ⅛" (laser-verified)

 1% slope to daylight (egress wells & drainage-critical items)

 Boom truck zone cleared (20 ft overhead + outriggers)

 811 called — utilities flagged

 Grade strings pulled at exact bottom elevation

 Inlet/outlet stubs 6" into hole (septic tanks)

 If installing a drain pipe daylighted 6" below base (egress wells) Text a photo to (406) 245-4635 — we’ll confirm before dispatch.

Common Hole Prep Mistakes by Product

Product	Mistake	Result	Fix
Cisterns/Septic	<3" gravel or pea gravel	Floor cracks	3"–6" ¾" minus only
Egress Wells	No 1% slope	Water pools	Slope base to daylight
Meter Vaults	Conduits buried in native soil	Crushed pipes	Bed in 6" gravel
Steps	Uneven 4" pad	Wobble in first winter	Laser-level pad

Ready for a Lifetime Lockwood Install?

A perfectly prepped hole = fast set, zero call-backs, happy clients. Need a custom drawing or site walk? Call (406) 245-4635 — we’ll send product-specific specs with every quote.

Lockwood Precast: Montana-made. Contractor-trusted. Built to last.  

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