How Proper Manhole Maintenance Reduces Environmental Impact

When manholes leak, the costs ripple through your entire system. Rain and groundwater that sneak in as inflow and infiltration (I/I) drive up wet-weather flows, overwhelm pumps, dilute treatment, and increase the odds of sanitary sewer overflows (SSOs)—events that threaten public health and water quality. Proactive maintenance—guided by standard inspection methods and proven rehab tools—cuts I/I, reduces SSO risk, and lowers energy and treatment costs. US EPA

Why manholes matter so much for I/I (and budgets)

Manholes are frequent entry points for unwanted water: through cracked barrels, porous mortar, leaky pipe penetrations, loose chimney/frame joints, and even the cover itself. Utilities and engineering groups routinely identify manholes as significant I/I contributors, especially at low points where stormwater ponds. Less I/I means fewer bypasses, fewer emergency callouts, and smaller utility bills for pumping and aeration. NASSCOMATSF

Environmental payoff: Each gallon of rainwater kept out of the sanitary system preserves treatment capacity for actual sewage, cutting the chance of SSOs and downstream impairments. That’s the core of EPA’s SSO and CMOM guidance. US EPA+1

A practical maintenance framework (CMOM-friendly)

EPA’s CMOM approach encourages utilities and property owners to manage collection systems proactively—inventory assets, inspect regularly, rehab before failure, and document everything. Manholes fit perfectly into this model: standardize your inspection method, triage defects, and prioritize the fixes that most reduce I/I and SSO risk. US EPA+1FedCenter

Step 1: Inspect consistently with a common language

Use NASSCO’s MACP (Manhole Assessment & Certification Program) coding so field notes translate into data you can rank and budget against. MACP creates consistent defect descriptions and severity scoring across your entire network. NASSCONASSCO

Step 2: Verify watertightness where it counts

For new or rehabilitated structures, many owners require ASTM C1244 vacuum testing before backfill to quickly prove manhole integrity. Local procedures often mirror C1244: plug openings, draw a set vacuum, and monitor allowable loss. ASTM International | ASTMDocHub

Step 3: Fix the fast leaks first

Prioritize defects with the biggest I/I impact and the lowest life-cycle cost to repair—typically cover/lid inflow, chimney/frame leaks, and pipe penetrations.

What to look for (and how to fix it)

1) Covers and frames: stop inflow at the surface

Symptoms: Water sheeting over lids enters through pickholes; lids rock on the frame; odors/pests escape.
Fixes: Upgrade to gasketed, bolted, watertight covers in flood-prone locations; add pickhole plugs; ensure machined bearing surfaces and sound seating. Keep frame elevations flush with pavement to avoid ponding. These small changes cut a common inflow path during storms. MATSF

2) Chimney and frame joints: seal the annulus

Symptoms: Infiltration at the frame-to-cone interface; seasonal leakage.
Fixes: Install mechanical or polymer chimney seals to create a continuous watertight barrier and accommodate thermal/settlement movement. This is a quick, non-excavation rehab with outsized effect on I/I. NASSCO

3) Pipe penetrations: make the connection flexible and tight

Symptoms: Weepers at pipe entries; annular leaks; root intrusion.
Fixes: Specify or retrofit flexible pipe-to-manhole connectors meeting ASTM C923 (compression boots or push-fit styles). These maintain a watertight seal while allowing differential movement between the structure and pipe. Hamilton Kentatlanticconcrete.com

4) Barrel defects and joints: grout and line strategically

Symptoms: Cracks, missing mortar, infiltration along horizontal joints.
Fixes: Chemical grouting (including “curtain” grouting) can stop multiple leaks in one mobilization; liners or coatings can follow for corrosion resistance. Use MACP data to target the right structures first. NASSCO

Safety note: manholes are permit-required confined spaces

Any inspection or rehab that requires entry must follow OSHA 29 CFR 1910.146: hazard evaluation, atmospheric testing, attendants, retrieval, and rescue planning. Sewer entries present unique hazards—don’t shortcut entry procedures. OSHA+1

KPIs that prove your maintenance program works

• Wet-weather flow ratio: Track plant influent vs. rainfall to see I/I trends fall after targeted manhole rehabs.

• SSO frequency and volume: CMOM expects documented reduction over time as you fix high-priority defects. US EPA

• Work orders per 100 structures: Fewer emergency responses indicate better condition and sealing.

• Pass rate on C1244 tests: Rising pass rates show construction quality is improving. ASTM International | ASTM

Cost & carbon: why maintenance saves money (and emissions)

I/I raises hydraulic load at lift stations and plants, increasing pumping energy and aeration demand. Eliminating lid inflow and sealing manholes lowers electricity use and chemical consumption—real operating dollars and indirect greenhouse gas savings. EPA’s SSO/CMOM resources frame these as key cost avoidance benefits of proactive maintenance. US EPA

Maintenance checklist (owner/operator ready)

Every 12–24 months (or after major storms)

• Visual/MACP inspection of covers, frames, barrels, and penetrations; document with photos and codes. NASSCO

• Check for rocking lids, missing gaskets/bolts, depressed frames, and ponding.

• Inspect chimney seals for tears or displacement; confirm pickhole plugs remain intact.

Upon rehab or installation

• Use C923 connectors at all penetrations; avoid mortar-only seals. Hamilton Kent

• Perform C1244 vacuum test prior to backfill; record results in your asset system. ASTM International | ASTM

After big rain events

• Patrol known low points; flag lids with visible inflow paths for fast-track upgrades. MATSF

Annually (program level)

• Roll up MACP data into a ranked rehab list; fund the top tier first.

• Update CMOM documentation and SSO metrics; present results to leadership. US EPA

 

Quick spec language you can adapt

• Watertight Cover & Frame (Traffic Rated): Provide bolted, gasketed, machined bearing surfaces; no open pickholes. Use at locations subject to ponding/flooding.

• Pipe Penetrations: Provide ASTM C923 flexible connectors (boot or push-fit).

• Acceptance: Manholes shall pass ASTM C1244 vacuum test prior to backfill; record results in the CMOM database. ASTM International | ASTMHamilton Kent

FAQs

How is inflow different from infiltration?
Inflow is stormwater entering through surface-connected pathways (e.g., lids, downspouts, cross-connections). Infiltration is groundwater entering through cracks and joints. Both raise flows and costs. Envirosight

Do I need watertight covers everywhere?
No. Prioritize sags, low spots, and areas with recurring ponding or SSOs. Pair lid upgrades with chimney seals and C923 connectors for best results. MATSFHamilton Kent

Is vacuum testing mandatory?
Requirements vary by owner, but ASTM C1244 is widely referenced for verifying manhole integrity before backfill. Many agencies adopt a local procedure based on C1244. ASTM International | ASTMDocHub

Who should perform inspections?
Use crews trained to MACP so defects are coded consistently and decisions are data-driven. For entries, follow OSHA’s permit-required confined space rules. NASSCOOSHA

Sources & further reading

• EPA: Sanitary Sewer Overflows—impacts and prevention; CMOM/SSO technical materials. US EPA+1

• EPA CMOM resources & self-assessment checklists (program design and documentation). US EPAFedCenter

• NASSCO: Manhole rehabilitation methods and MACP defect coding. NASSCONASSCO

• ASTM C1244: Vacuum testing of precast concrete manholes; common agency procedures mirror this test. ASTM International | ASTMDocHub

• ASTM C923: Flexible pipe-to-manhole connectors (boot/push-fit) to maintain watertight penetrations. Hamilton Kent

• I/I primer: How lid and connection leaks drive flows and costs. MATSF