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Sewer Flow Monitoring
& Capacity Studies

PE-stamped field data for the engineers who build infrastructure. Fixed-scope pricing, nationwide coverage, proposals within 24 hours.

PE-StampedFixed-Scope Pricing2-Week MobilizationAll 50 States
30–65%
Typical model overestimation
7–14d
Capacity study turnaround
50
States covered
~24hr
From call to proposal
(855) 872-8233Call for a quote

Service Offerings

Six Core Service Areas

Covering the full lifecycle of sewer system analysis — from development approval to long-term asset management and regulatory compliance.

All Clients

Sewer Flow Monitoring

Continuous measurement of wastewater flow rate, velocity, and depth. Cellular telemetry with near real time uploads. 95%+ data uptime target.

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Civil Firms & Developers

Sewer Capacity Studies

PE-stamped certification for building permits, sewer connection agreements, and development entitlements. Most studies complete in 7–14 days.

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Municipalities & Utilities

RDII Analysis

RTK unit hydrograph method. Supports CMOM programs, EPA consent decree compliance, SSO reduction, and CIP prioritization.

Learn More
Hydraulic Modeling Engineers

Hydraulic Model Calibration

15-minute DWF diurnal datasets for EPA SWMM, InfoWorks ICM, SewerGEMS, XPSWMM, and ESRI. Ready for direct import.

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Field Services

Flow Meter Installation

Professional area-velocity sensor installation per OSHA confined-space protocols. Site photos and velocity profile verification included.

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Municipalities

CMOM Program Support

Long-term monitoring for EPA consent decree milestones, CMOM capacity assessments, and sanitary sewer evaluation surveys (SSES).

Learn More

Engagement Process

From Call to Certified Report

Fixed-scope pricing. Most studies mobilize within two weeks. No open-ended billing.

01
You Contact Us

Submit Project Details

Call (855) 872-8233 or submit the quote form with project location, study type, and timeline.

02
~24 Hr Response

Fixed-Scope Proposal

US3 delivers a fixed-fee proposal with scope, monitoring locations, duration, and timeline.

03
7–56 Days On-Site

Deployment & Monitoring

Area-velocity sensors deployed per OSHA protocols. Cellular telemetry and near real time uploads throughout.

04
Ready for Submittal

PE-Stamped Report

Technical report plus PE-stamped certification letter. Draft reviewed before final seal is applied.

Trusted by Municipalities and Utilities

Experience & Expertise

20+
Years serving municipalities
50
States covered
PE
Stamped certifications
OSHA
Compliant field crews

Case Studies

What Field Data Reveals

Models built on assumptions routinely misrepresent actual conditions. These are the corrections measured data made possible.

65%
Model overestimation
Before$42M
After$10M

Field data corrected a trunk sewer replacement

A 47-meter monitoring network revealed the city's hydraulic model had overestimated peak flows by 65%.

84%
CIP reduction
Before$28M
After$4.4M

Monitoring changed the diagnosis entirely

18-month monitoring identified inflow defects — not deteriorated pipe — as the primary SSO source.

10.6×
Data ROI
Before$890K
After$4.1M

Monitoring investment that funded itself

Three monitoring programs generated calibration data that justified $4.1M in follow-on engineering contracts.

"I reviewed the flow report and everything looks great. I am always very pleased to work with your team and very satisfied with the services US3 provides."

Process Engineer — Municipal Utility Client

All Clients

Sewer Flow Monitoring

Continuous measurement of wastewater flow rate, velocity, and depth. Cellular telemetry with near real time uploads. 95%+ data uptime target.

Learn More
Civil Firms & Developers

Sewer Capacity Studies

PE-stamped certification for building permits, sewer connection agreements, and development entitlements. Most studies complete in 7–14 days.

Learn More
Municipalities & Utilities

RDII Analysis

RTK unit hydrograph method. Supports CMOM programs, EPA consent decree compliance, SSO reduction, and CIP prioritization.

Learn More
Hydraulic Modeling Engineers

Hydraulic Model Calibration

15-minute DWF diurnal datasets for EPA SWMM, InfoWorks ICM, SewerGEMS, XPSWMM, and ESRI. Ready for direct import.

Learn More
Field Services

Flow Meter Installation

Professional area-velocity sensor installation per OSHA confined-space protocols. Site photos and velocity profile verification included.

Learn More
Municipalities

CMOM Program Support

Long-term monitoring for EPA consent decree milestones, CMOM capacity assessments, and sanitary sewer evaluation surveys (SSES).

Learn More

What This Service Is

Sewer flow monitoring is the continuous measurement of wastewater velocity, depth, and flow rate inside active sewer manholes. US3 installs area-velocity sensors, connects each meter to cellular telemetry, and provides near real time data uploads throughout the monitoring period. The result is a defensible, PE-stamped engineering record of how a sanitary sewer system actually behaves under dry weather and wet weather conditions.

Why Municipal Utilities Need It

Hydraulic models built on assumed flows routinely misrepresent actual system conditions by 30–65%. That margin of error leads to oversized capital projects, wrong rehabilitation priorities, and capacity evaluations that fail under regulatory review. Measured field data replaces assumptions with evidence.

Common applications include sewer capacity certification for new development, RDII quantification for consent decree compliance, hydraulic model calibration, SSO source identification, and CMOM program capacity assessments. Municipalities, utilities, and regulators require measured flow data for permit applications, capital improvement planning, and development entitlements.

How the Process Works

Area-velocity sensors measure velocity via Doppler or electromagnetic induction and depth via ultrasonic transducers. Flow rate is calculated as Q = A × V. Each installation follows OSHA 29 CFR 1910.146 confined-space protocols and is documented with site photos and velocity profile verification.

Cellular telemetry transmits data with near real time uploads to US3 engineering staff. Anomalies are flagged immediately — not discovered weeks later. US3 targets 95%+ data uptime on every engagement.

Typical Project Workflow

US3 reviews GIS data and as-built drawings to select optimal monitoring locations, deploys sensors per OSHA protocols, transmits data via cellular telemetry with continuous engineering review, and delivers a PE-stamped technical report with certified flow data.

Capacity studies: 7–14 days. I/I and RDII studies: 30–56 days. Model calibration: 3–6 months. Consent decree programs: 12–18 months. Proposals delivered within approximately 24 hours of initial contact.

Learn more: What Is Sewer Flow Monitoring?

Request a Quote

Fixed-scope proposals within approximately 24 hours. No open-ended billing.

What This Service Is

A sewer capacity study measures existing flow conditions in a downstream sewer to determine whether adequate hydraulic capacity exists for a proposed development. The deliverable is a PE-stamped certification letter that the municipality accepts as engineering evidence of available capacity.

Why Municipal Utilities Need It

Municipalities require capacity studies to protect existing ratepayers from capacity-related service failures. Common triggers include building permit applications, sewer connection agreements, development entitlements and Environmental Impact Reports, and master plan updates requiring documentation of existing conditions.

How the Process Works

Step 1 — Site Design: US3 reviews GIS data and as-built drawings to identify the critical downstream monitoring location.

Step 2 — Flow Monitoring: Area-velocity sensors are deployed in manholes per OSHA protocols. Cellular telemetry provides near real time data uploads.

Step 3 — Analysis: US3 establishes average daily flow, peak hour flow, and minimum night flow, then evaluates the hydraulic grade line under projected conditions including the proposed development.

Step 4 — PE Certification: A PE-stamped certification letter is issued confirming available capacity or identifying required improvements.

Typical Project Workflow

Most studies complete in 7–14 days of dry weather monitoring. US3 delivers fixed-scope proposals within approximately 24 hours and mobilizes within two weeks. The certification letter is formatted for direct submittal to the reviewing municipality.

Learn more: How Sewer Capacity Studies Work

Request a Quote

Fixed-scope proposals within approximately 24 hours. No open-ended billing.

What This Service Is

RDII analysis quantifies the volume and timing of stormwater entering the sanitary sewer during and after rainfall events. US3 uses the EPA-standard RTK unit hydrograph method to calibrate three parameters for each monitored sub-basin: R (fraction of rainfall entering as RDII), T (time to peak), and K (recession ratio).

Why Municipal Utilities Need It

RDII is the primary driver of wet weather sanitary sewer overflows. Infiltration enters through deteriorated joints and cracked pipes — a slow response building over hours. Inflow enters through illicit connections and damaged manholes — a rapid response tracking rainfall. Each requires different rehabilitation. US3 separates and quantifies both components by sub-basin, directing investment where it has the greatest measurable impact on SSO reduction.

How the Process Works

Flow monitoring over 30–56 days captures multiple storm events. Co-located rain gauges record precipitation at 1-minute intervals. US3 engineers then calibrate RTK parameters against observed flow response — these are the direct inputs required by EPA SWMM and other hydraulic models for wet weather simulation.

Typical Project Workflow

Applications include EPA consent decree compliance, Sanitary Sewer Evaluation Surveys (SSES), CMOM program capacity assessments, SSO source identification, and capital improvement program justification.

Learn more: What Is RDII in Sewer Systems?

Request a Quote

Fixed-scope proposals within approximately 24 hours. No open-ended billing.

What This Service Is

US3 provides field-measured calibration data that makes hydraulic models accurate. Models built on assumed flow patterns misrepresent actual conditions by 30–65% — leading to oversized capital projects and capacity evaluations that fail under regulatory review.

Why Municipal Utilities Need It

Regulators and permitting agencies require hydraulic models calibrated against measured field data. Uncalibrated models are not accepted for consent decree submittals, capacity certifications, or capital improvement justifications.

How the Process Works

DWF Diurnal Patterns: 15-minute interval dry weather flow time series — average daily flow, peak hour flow, and minimum night flow derived from continuous sewer flow monitoring.

RDII Parameters: R, T, and K values calibrated against observed storm events using SSOAP software — direct inputs for EPA SWMM and similar platforms.

Compatible platforms: EPA SWMM, InfoWorks ICM, SewerGEMS, XPSWMM, ESRI. US3 coordinates format requirements with your modeling engineer before fieldwork begins.

Typical Project Workflow

DWF calibration: 14–21 days minimum. Full DWF + RDII calibration: 3–6 months. US3 delivers interim DWF data early while wet weather collection continues.

Request a Quote

Fixed-scope proposals within approximately 24 hours. No open-ended billing.

What This Service Is

Installing a sewer flow meter is a permit-required confined-space operation governed by OSHA 29 CFR 1910.146. US3 handles site selection, atmospheric testing, sensor deployment and calibration, telemetry configuration, and initial data verification — documented with site photographs, manhole geometry measurements, and velocity profile confirmation.

Why Municipal Utilities Need It

The quality of flow monitoring data depends directly on correct sensor placement and calibration. Properly installed area-velocity sensors achieve ±5% accuracy. Poor installation produces unreliable data that cannot support engineering decisions or regulatory submittals.

How the Process Works

Site Selection: US3 reviews GIS data and as-built drawings to identify locations that maximize tributary coverage while ensuring stable, measurable flow conditions.

Confined Space Entry: Pre-entry atmospheric testing for oxygen deficiency, combustible gases, H₂S, and CO. Entry supervisor, authorized entrant, and attendant assigned for every installation.

Telemetry Setup: Cellular telemetry transmits readings continuously, enabling near real time uploads and anomaly detection. Rain gauges co-located for wet weather programs.

Typical Project Workflow

US3 mobilizes installation crews within two weeks of contract execution. Each installation includes deployment, calibration verification, telemetry confirmation, and complete site documentation.

Learn more: How Sewer Flow Meters Are Installed

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Fixed-scope proposals within approximately 24 hours. No open-ended billing.

What This Service Is

Capacity Management Operations and Maintenance (CMOM) is EPA's framework for managing sanitary sewer collection systems. EPA requires CMOM programs from municipalities with administrative orders or consent decrees related to sanitary sewer overflows. Sewer flow monitoring data is the evidentiary foundation of any credible CMOM program.

Why Municipal Utilities Need It

EPA consent decrees require documenting existing flow conditions at SSO locations, quantifying RDII using an EPA-accepted methodology, demonstrating progress toward SSO elimination milestones, providing regulators with ongoing access to monitoring data, and reporting on capacity improvements. US3 cellular telemetry provides EPA-visible dashboards accessible by regulators in real time.

How the Process Works

CMOM monitoring programs typically run 12–18 months to capture seasonal variation and sufficient storm events for robust RTK calibration. US3 structures programs with interim deliverables so municipalities receive actionable data throughout.

Typical Project Workflow

US3 also provides rehabilitation effectiveness tracking — measuring sub-basin RDII before and after pipe rehabilitation to document the actual flow reduction achieved. This before-and-after evidence is what consent decree administrators require.

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Fixed-scope proposals within approximately 24 hours. No open-ended billing.

Sewer flow monitoring is the process of continuously measuring wastewater velocity, depth, and flow rate inside active sanitary sewer manholes. Engineers use this data to understand how a collection system behaves under both dry weather and wet weather conditions — replacing assumptions with measured evidence.

How Area-Velocity Sensors Work

The standard instrument for sewer flow monitoring is an area-velocity sensor installed on the pipe invert inside a manhole. These sensors measure two parameters simultaneously: the velocity of the wastewater stream and the depth of flow above the sensor.

Velocity is measured using either Doppler ultrasonic technology (which bounces sound waves off particles suspended in the wastewater) or electromagnetic induction (which measures the speed of conductive fluid passing through a magnetic field). Depth is measured using an ultrasonic transducer aimed upward from the sensor to the water surface.

Flow rate is then calculated using the continuity equation: Q = A × V, where Q is flow rate, A is the cross-sectional area of flow (derived from depth measurement and known pipe geometry), and V is the measured average velocity. At a typical 15-minute recording interval, this produces 96 flow measurements per day per monitoring location.

Why Municipalities Require Flow Monitoring

Municipalities and utilities require measured sewer flow data for several critical engineering and regulatory purposes:

Capacity certification for new development depends on measured peak flows, not estimates. Without a PE-stamped capacity study, municipalities cannot issue building permits or sewer connection agreements.

EPA consent decree compliance requires documented flow conditions. Federal consent decrees mandate that municipalities demonstrate understanding of their system's actual capacity and wet weather response using measured data.

Hydraulic model calibration needs measured diurnal patterns and wet weather response data. Models built on assumed flows routinely overestimate or underestimate actual conditions by 30–65%, leading to misallocated infrastructure spending that can reach tens of millions of dollars.

Capital improvement programs must be justified with field-measured evidence of capacity deficiencies. Regulatory agencies and municipal bond underwriters require measured data to support infrastructure investment decisions.

Types of Sewer Flow Monitoring Programs

Capacity studies typically require 7–14 days of dry weather monitoring to establish baseline flow conditions. These short-term programs produce the average daily flow, peak hour flow, peak-to-average ratio, and minimum night flow parameters needed for capacity certification.

RDII studies require 30–56 days to capture multiple storm events for wet weather analysis. Rain gauges are co-located to record precipitation at 1-minute intervals, allowing engineers to correlate rainfall with sewer flow response and quantify the volume of stormwater entering the sanitary system.

Model calibration programs run 3–6 months to capture seasonal variation in flow patterns, including summer vs. winter diurnal curves and response to storms of varying intensity and duration.

Consent decree programs run 12–18 months for comprehensive system characterization. These long-term programs capture the full range of seasonal conditions and provide the sustained monitoring record required by EPA enforcement actions.

Data Quality and Telemetry

Modern sewer flow monitoring uses cellular telemetry to transmit data from field sensors to engineering staff in near real time. This allows daily quality assurance review, immediate detection of sensor issues or anomalous flow events, and remote access to monitoring data without field visits. Professional monitoring programs target 95%+ data uptime — meaning usable, quality-verified data for at least 95% of the monitoring period.

Industry Standards and Safety

All sewer flow monitoring installations require confined space entry under OSHA 29 CFR 1910.146, including atmospheric testing, assigned entry roles, and continuous monitoring during manhole entry. The flow meter installation process follows established industry practices recognized by EPA SWMM, InfoWorks ICM, SewerGEMS, XPSWMM, and ESRI modeling platforms.

Need this service? Learn about our sewer flow monitoring services or request a quote.

Request a Quote

Fixed-scope proposals within approximately 24 hours. No open-ended billing.

RDII stands for Rainfall Dependent Infiltration and Inflow. It refers to stormwater that enters the sanitary sewer system during and after rainfall events through defects in the collection system infrastructure. RDII is the primary cause of wet weather capacity problems in sanitary sewers, including sanitary sewer overflows (SSOs), treatment plant surcharging, and basement flooding.

What Causes RDII?

RDII has two distinct components that enter the sewer through different mechanisms and require different rehabilitation approaches:

Infiltration is groundwater that enters the sewer through deteriorated pipe joints, cracked pipe walls, and failed service laterals. When rainfall raises the groundwater table, this water is pushed into the sewer through every defect below the water table. Infiltration produces a slow, sustained flow increase that builds over hours to days after rainfall and can persist for days after rain stops as the water table slowly recedes.

Inflow is surface stormwater that enters the sewer directly through illicit connections (such as roof drains or area drains connected to the sanitary sewer), damaged manhole covers that allow surface water to pour in, cross-connected storm drains, and foundation drains that are improperly connected to the sanitary system. Inflow produces a rapid flow response that closely tracks rainfall intensity — flow rises quickly when rain starts and drops quickly when rain stops.

Why the Distinction Matters

Infiltration is addressed through structural rehabilitation: pipe lining (CIPP), joint sealing, manhole rehabilitation, and lateral replacement. Inflow is addressed by locating and disconnecting illicit connections, repairing manhole structures, replacing damaged covers, and redirecting improperly connected drains.

Without RDII analysis that separates these components, a municipality might spend millions rehabilitating pipe when the actual problem is illicit inflow connections — or vice versa. Accurate RDII quantification by sub-basin directs rehabilitation investment to the locations and mechanisms that produce the greatest measurable reduction in SSO risk.

How Engineers Quantify RDII — The RTK Method

The industry-standard method for quantifying RDII is the EPA RTK unit hydrograph approach, which is built into EPA SWMM and other hydraulic modeling platforms. Engineers calibrate three parameters for each monitored sub-basin:

R (Volume fraction) — the fraction of total rainfall volume that enters the sewer as RDII. Higher R values indicate more stormwater is entering the system. Typical values range from 0.01 (1% of rainfall) to 0.15 (15% of rainfall), with values above 0.05 generally indicating significant defects.

T (Time to peak) — the time from the center of a rainfall event to the peak of the RDII flow response. Short T values indicate inflow-dominated response; longer T values indicate infiltration-dominated response.

K (Recession ratio) — describes how quickly RDII flow decreases after the peak. This parameter captures the "tail" of the RDII response and is important for modeling how long elevated flows persist after rain stops.

These three parameters are calibrated by matching modeled flow hydrographs to observed flow monitoring data during multiple storm events. The calibrated R, T, and K values become the direct inputs for hydraulic model wet weather simulation.

Why RDII Analysis Matters for Municipalities

EPA consent decrees require municipalities to quantify RDII as part of corrective action planning. RDII data identifies which sub-basins contribute the most stormwater to the sanitary sewer, allowing rehabilitation investment to target the highest-impact areas first. Without RDII data, municipalities cannot justify capital improvement programs, demonstrate consent decree compliance, or prioritize SSO reduction efforts based on engineering evidence.

Need this service? Learn about our rdii analysis services or request a quote.

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Fixed-scope proposals within approximately 24 hours. No open-ended billing.

A sewer capacity study is an engineering investigation that measures existing flow conditions in a downstream sewer to determine whether adequate hydraulic capacity exists to accommodate additional flow from a proposed development, redevelopment, or system modification.

Why Are Sewer Capacity Studies Required?

Most municipalities require a sewer capacity study before issuing building permits, sewer connection agreements, or development entitlements. The purpose is to protect existing ratepayers by ensuring that new connections will not cause capacity-related service failures, surcharging, or overflows in the downstream collection system.

The deliverable is typically a PE-stamped certification letter — a document signed and sealed by a licensed Professional Engineer stating that the downstream sewer has adequate capacity for the proposed additional flow, or identifying what system improvements would be needed to accommodate it.

Step 1: Site Selection and Scoping

The study begins with an engineering review of the downstream sewer system. The engineer examines GIS data, as-built drawings, pipe diameters, slopes, and system topology to identify the critical monitoring location — the point in the downstream system where capacity is most likely to be constrained.

Factors in site selection include pipe size transitions, changes in slope, confluences where multiple tributary sewers combine, and locations where previous studies or model results suggest limited available capacity. Selecting the right location is as important as the monitoring itself — monitoring in the wrong place can miss the actual capacity bottleneck.

Step 2: Flow Monitoring

Area-velocity flow meters are installed in the selected manhole following OSHA confined-space protocols. The sensors record velocity and depth at 5 or 15-minute intervals, transmitted via cellular telemetry for near real time quality assurance review.

Most capacity studies require 7–14 days of dry weather monitoring. The monitoring period must be long enough to capture representative weekday and weekend flow patterns and must avoid periods influenced by unusual events (holidays, construction dewatering, or significant rainfall) that would distort baseline conditions.

Step 3: Hydraulic Analysis

From the monitoring data, the engineer establishes baseline flow parameters: average daily flow (ADF), peak hour flow, peak-to-average ratio (peaking factor), and minimum night flow. The engineer then projects future conditions by adding the proposed development flows to the measured baseline, applying appropriate peaking factors, and evaluating whether the downstream pipe can convey the combined flow without surcharging above acceptable thresholds.

Step 4: PE Certification

The final deliverable is a PE-stamped certification letter that includes a clear statement of available capacity (or required improvements), a summary of measured flow conditions, the monitoring methodology and data quality assessment, projected flow conditions with the proposed development, and the engineer's professional seal and signature. This document is formatted for direct submittal to the reviewing municipality or utility district. The complete process from contract execution to certification letter typically takes 3–4 weeks.

Need this service? Learn about our sewer capacity studies services or request a quote.

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Fixed-scope proposals within approximately 24 hours. No open-ended billing.

Sanitary sewer overflows (SSOs) occur when wastewater escapes from the collection system before reaching the treatment plant. SSOs are regulated under the Clean Water Act and can result in EPA consent decrees, significant fines, and mandatory corrective action programs that can cost municipalities tens of millions of dollars. Understanding the engineering root causes is the first step toward prevention.

Rainfall Dependent Infiltration and Inflow (RDII)

RDII is the most common cause of wet weather SSOs nationwide. During and after rainfall events, stormwater enters the sanitary sewer through two mechanisms: infiltration (groundwater entering through pipe defects) and inflow (surface water entering through illicit connections and damaged structures). During intense storms, RDII can increase sewer flows by 500–1000% above dry weather conditions, overwhelming system capacity.

RDII-caused SSOs are addressed through systematic RDII quantification by sub-basin, followed by targeted rehabilitation of the pipe defects and illicit connections contributing the most stormwater volume.

Hydraulic Capacity Deficiencies

Undersized pipes, inadequate slope, and system growth beyond original design capacity create permanent bottlenecks where flow exceeds pipe capacity even under dry weather conditions. These structural capacity deficiencies are identified through sewer capacity studies that measure actual flow conditions and compare them to pipe capacity — rather than relying on model assumptions that frequently overestimate or underestimate conditions by 30–65%.

Blockages and Structural Failures

Grease accumulation, root intrusion, debris, sediment buildup, and structural pipe failures (such as collapsed pipe sections or offset joints) can partially or completely block flow, causing localized overflows even when overall system capacity is adequate. These are typically identified through CCTV inspection programs and addressed through cleaning, root treatment, or point repairs.

Pump Station and Force Main Failures

Mechanical failures, power outages, and inadequate pump capacity at lift stations can cause overflows in systems that rely on pressure sewers to convey flow over hills or across water features. Flow monitoring programs can identify pump stations operating near capacity limits before failures occur.

Combined Sewer System Issues

Older cities with combined sewer systems (which carry both sanitary sewage and stormwater in the same pipes) experience CSOs (combined sewer overflows) during rainfall. While technically different from SSOs, the monitoring and analysis techniques are similar, and many municipalities are under consent decrees to address both.

How Flow Monitoring Prevents SSOs

Sewer flow monitoring provides the measured data needed to identify which specific causes are driving SSOs in a particular system. This data directs rehabilitation investment to the locations and causes that produce the greatest measurable reduction in overflow risk — preventing municipalities from spending capital on the wrong problems. The monitoring data also provides the before-and-after evidence required to demonstrate that corrective actions are actually working, which is essential for consent decree compliance.

Need this service? Learn about our sewer flow monitoring services or request a quote.

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Fixed-scope proposals within approximately 24 hours. No open-ended billing.

Installing a sewer flow meter requires entering an active sanitary sewer manhole — a permit-required confined space under OSHA 29 CFR 1910.146. Professional installation ensures accurate data collection, worker safety, and compliance with federal safety regulations.

Step 1: Pre-Installation Planning

Before any equipment is deployed, engineers review GIS data, as-built drawings, and pipe records to select monitoring locations that will produce the most useful data. Key selection criteria include pipe material and diameter (which affect sensor compatibility), pipe slope (which affects flow stability), upstream and downstream conditions (confluences, transitions, and potential backwater), access conditions (manhole depth, traffic exposure, physical accessibility), and tributary area served by the monitoring point.

The goal is to identify locations where flow is stable, measurable, and representative of the tributary area — while also being safe and practical to access for installation and maintenance.

Step 2: OSHA Confined Space Entry

Every sewer manhole entry requires a complete confined space entry procedure. Before any person enters the manhole, the entry team conducts atmospheric testing using a calibrated four-gas monitor to check for oxygen deficiency (below 19.5%), oxygen enrichment (above 23.5%), combustible gas concentration (LEL above 10%), hydrogen sulfide (H₂S above 10 ppm), and carbon monoxide (CO above 25 ppm).

Three designated roles are assigned for every entry: the entry supervisor (who authorizes the entry and monitors conditions), the authorized entrant (who enters the manhole), and the attendant (who remains at the surface and maintains communication). Continuous atmospheric monitoring is maintained throughout the entry, and rescue equipment is staged at the manhole opening.

Step 3: Sensor Mounting and Positioning

Area-velocity sensors are mounted on the pipe invert (the lowest point of the pipe cross-section) using mechanical brackets, stainless steel banding, or expansion anchors depending on pipe material and diameter. The sensor must be positioned to measure the full velocity profile across the flow stream — not just the surface velocity or bottom velocity, which are not representative of the average cross-sectional velocity.

For pipes with significant sediment deposits, the installation team may need to clean the invert area before mounting the sensor to ensure proper contact and accurate depth measurement.

Step 4: Calibration Verification

After the sensor is mounted, the installation team performs an initial velocity profile verification. This involves comparing the sensor's velocity reading against a reference measurement (typically a point velocity meter at multiple depths) to confirm that the installed sensor is producing accurate results. The depth measurement is verified against a physical depth measurement using a graduated rod.

Step 5: Telemetry Configuration

A cellular telemetry unit is installed at the surface, connected to the submerged sensor by shielded cable routed through the manhole frame. The telemetry unit is configured to record and transmit data at programmed intervals — typically every 5 or 15 minutes — to a cloud-based data management system. This enables near real time data uploads and remote quality assurance without requiring repeated field visits.

Step 6: Documentation

Every installation is documented with site photographs (manhole exterior, interior, sensor placement, telemetry unit), manhole geometry measurements (depth, pipe diameters, invert elevations), sensor placement diagrams, pipe condition observations, and initial velocity profile data. This documentation becomes part of the permanent project record and supports the quality assurance process throughout the monitoring period.

Need this service? Learn about our flow meter installation services or request a quote.

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Fixed-scope proposals within approximately 24 hours. No open-ended billing.

Sewer flow monitoring is the continuous measurement of wastewater velocity, depth, and flow rate inside active sewer manholes using area-velocity sensors and cellular telemetry. Read our complete guide.
A sewer capacity study measures existing flow conditions to confirm adequate hydraulic capacity for proposed development. Municipalities require PE-stamped certification before issuing building permits. Learn how capacity studies work.
Capacity studies: 7–14 days. I/I and RDII studies: 30–56 days. Hydraulic model calibration: 3–6 months. Consent decree programs: 12–18 months. US3 delivers proposals within approximately 24 hours.
RDII is stormwater entering the sanitary sewer during rain events — the primary cause of wet weather SSOs. US3 quantifies it using the EPA RTK method. Read our complete RDII guide.
Capacity Management Operations and Maintenance is EPA's framework for managing sanitary sewer systems. US3 provides the flow monitoring data that forms the evidentiary foundation of CMOM programs. Learn about our CMOM support.
Yes. All US3 datasets are formatted for direct import into EPA SWMM, InfoWorks ICM, SewerGEMS, XPSWMM, and ESRI — including 15-minute DWF diurnal patterns, peaking factors, and RTK-calibrated RDII parameters.
US3 operates in all 50 states with additional coverage in Canada and Mexico. Call (855) 872-8233 to confirm availability.
Flow meters are installed in active sewer manholes following OSHA 29 CFR 1910.146 confined-space protocols. Read our installation guide.

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Fixed-scope proposals within approximately 24 hours. No open-ended billing.

US3 is headquartered in Santa Ana, California, and has provided sewer flow monitoring, capacity study certification, and RDII analysis to California municipalities, utility districts, and civil engineering firms since 2002.

California Services

California municipalities require PE-stamped sewer capacity studies before issuing building permits and sewer connection agreements. US3 delivers fixed-scope capacity certifications with typical turnaround of 3–4 weeks. Our California services include sewer flow monitoring for development entitlements, RDII analysis for Regional Water Quality Control Board compliance, hydraulic model calibration data for SWMM and InfoWorks ICM, flow meter installation per Cal/OSHA confined-space requirements, and long-term monitoring for consent decree and SSMP compliance.

Service Area

US3 serves all California counties and utility districts from our Santa Ana headquarters at 601 N Parkcenter Dr #209, Santa Ana, CA 92705. Call (855) 872-8233 for a project-specific proposal.

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Fixed-scope proposals within approximately 24 hours. No open-ended billing.

US3 provides sewer flow monitoring, capacity studies, and RDII analysis to Texas municipalities, utility districts, and engineering firms. Texas sewer systems face unique challenges including high RDII volumes from expansive clay soils and rapidly growing urban areas that strain legacy collection system capacity.

Texas Services

Texas municipalities and MUDs require sewer capacity verification for new development approvals and TCEQ compliance. US3 provides fixed-scope flow monitoring programs, PE-stamped capacity certifications, RDII quantification for SSO reduction planning, hydraulic model calibration for SWMM and SewerGEMS, and long-term monitoring for TCEQ consent orders and compliance schedules.

Coverage

US3 deploys monitoring equipment throughout Texas. Call (855) 872-8233 to discuss your project timeline and scope.

Request a Quote

Fixed-scope proposals within approximately 24 hours. No open-ended billing.

US3 provides sewer flow monitoring, capacity studies, and RDII analysis to Florida municipalities, utility authorities, and engineering firms. Florida's high groundwater table and frequent intense rainfall create significant RDII challenges for sanitary sewer systems statewide.

Florida Services

Florida utilities face unique wet weather challenges including high infiltration rates from elevated groundwater, intense storm events that produce rapid inflow response, and FDEP consent order requirements for SSO reduction. US3 provides sewer flow monitoring, PE-stamped capacity certifications, RDII analysis for FDEP compliance, hydraulic model calibration data, and long-term CMOM monitoring programs.

Coverage

US3 deploys monitoring equipment throughout Florida. Call (855) 872-8233 to discuss your project.

Request a Quote

Fixed-scope proposals within approximately 24 hours. No open-ended billing.

What US3 Does

US3 exists to answer one question for engineers, municipalities, and developers: does this sewer system have the capacity to handle the flows being put into it? We answer with measured field data — not assumptions — sealed with a licensed Professional Engineer's stamp.

Our practice is built around collecting, validating, and delivering high-quality sewer flow monitoring data. We do not build models, design infrastructure, or manage construction. This focused scope means our clients receive data services from specialists, not generalists.

Engineering Tools & Methods

  • Modeling platforms: EPA SWMM, InfoWorks ICM, SewerGEMS, XPSWMM, ESRI
  • Analysis methods: RTK Unit Hydrograph, DWF Diurnal Analysis, RDII Quantification, Area-Velocity Measurement, SSOAP
  • Regulatory contexts: EPA Consent Decrees, CMOM Programs, Development Entitlements, Master Plan Updates, SSES

Company Information

Founded: 2002 · Coverage: All 50 states, Canada, Mexico

Address: 601 N Parkcenter Dr #209, Santa Ana, CA 92705

Phone: (855) 872-8233 · Email: sales@uscubed.com

Our Team

Licensed Professional Engineers

Every US3 study is prepared and sealed by a PE with direct experience in municipal wastewater systems and EPA compliance.

Mark Serres, Electrical Engineer specializing in sewer monitoring systems
Mark Serres
Electrical Engineer — 30+ Years

GIS data collection, CMOM programs, wastewater conveyance design, combined and sanitary gravity sewer modeling.

Darlene Szczulewski PE, Civil Engineer specializing in water resources and flow monitoring
Darlene Szczulewski, PE
Civil Engineer — Water Resources

12+ years in water resources and flow monitoring across urban, rural, and government utility projects nationwide.

Tom Williams PE, Engineering Manager with 24+ years in wastewater systems
Tom Williams, PE
Engineering Manager — 24+ Years

CMOM programs, treatment facility design, discharge facility engineering, gravity sewer modeling.

"I reviewed the flow report and everything looks great. I am always very pleased to work with your team and very satisfied with the services US3 provides."

Process Engineer — Municipal Utility Client

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Or call (855) 872-8233 to schedule a consultation

Call Us Directly
(855) 872-8233

Leave a message anytime — we return calls same business day.

Office

601 N Parkcenter Dr #209
Santa Ana, CA 92705

Response Time

Proposals within approximately 24 hours

Mobilization

Most studies deploy within 2 weeks of contract

Ready to discuss your project?

Fixed-scope proposals within approximately 24 hours. No open-ended billing.

Request a Quote(855) 872-8233
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