H1 Risk Assessment

There are four major steps in completing an H1 Risk Assessment, the first is to identify the risks associated with your permitted activity, the second is to assess those risks, the third to decide on appropriate measures (and to justify those measures, and finally to present your findings to the Regulator (Environment Agency).

If you have any question regarding H1 Risk Assessments in connection with Environmental Permits then please contact SWEL for a free initial consultation.

H1 Risk Assessment - Case Study - Typical Procedure & Data Requirements

SWEL have completed numerous H1 Assessments for various installations and discharge activities. The "meat" of the work is finding the data to put into the assessment, the rest is quite easy. The job can be very quick if the data is to hand but in most cases it is not, which may require monitoring or consultations with various bodies. For a H1 assessment for an Installation Permit we would require quite a lot of data.

Indirect Emissions

This covers thing like electricity use . . . . global warming potential and the likes.

Direct Emissions

This would deal with discharges to water, air and land. In each case you will need a wealth of data in order to populated the H1 software. The Environment Agency ordinarily insist on MCerts accredited monitoring. An example might be NOx, SOx or POx.

Environmental Data

River flow by volume, water quality and air quality, these are required to populate the H1 Assessment Software.

H1 Software Use

Once you have all of you data in place, this is put in to the H1 Software (which is freely available) and hopefully when you consider the volume of output, the concentration of output, the back ground level and the dilution and dispersion, then the substances such as lead, or copper will "screen out" if they do then this is good news. If they do not then you will either have to upgrade your abatement or treatment systems or undertake detailed modeling.

Detailed Monitoring

If the H1 tool does not screen out for a particular substance, then detailed modeling will have to be undertaken. This involves using a program such a aermod, to calculate concentration of certain substances at certain points. You may avoid abatement & treatment upgrades if it can be shown that concentrations are acceptable at nearby receptor locations.

H1 Risk Assessment - Air Impacts: Stage One Screening &  Stage Two Screening

There are two screening levels within the the Air Impacts section of the  H1 modeling software:

Stage 1 Screening

If you process contribution (emission) greater than 1% or 10% of the EAL (Environmental Assessment Level) then it will screen out at this stage. The EAL for different substances depends on the potential for harm that they have. For example PM10 particulates are thought to be less harmful than than PM2.5 Particulates and as such have a higher EAL. Some substances such a Chromium 6 have a very very low EAL. Because they are intensely carcinogenic.

Stage 2 Screening

In stage two screening various additional variables are added to the model. The main additional variable is Background Concentration. This can help of hinder you cuase in terms of screening out, but in our experience you are more likely to screen out at Stage 2 rather than Stage 1.

H1 Risk Assessment - Abatement

When you have received the monitoring data (as above) it is time to start experimenting within the H1 modeling software to see whether you will need abatement. The key here is to have conducted the right kind of monitoring. Each set of monitoring may take a month or so to arrange, it is best to get it all done in one hit. The way to do this is set up a test rig which includes an array of abatement technologies, say a scrubber, a centrifuge and a GAC filter. Monitoring is done at each stage of the test rig. This allows you to obtain data for a variety of abatement options simultaneously.

H1 Abbreviations

BAT - Best Available Technique
BATAEL - Best Available Technique Associated Emissions Level
EAL - Environmental Assessment Level
EQS - Environmental Quality Standard
H - Horizontal (Guidance)
NCCC - National Customer Contact Centre
OPRA - Operational Risk Appraisal
PC - Process Contribution
PEC - Predicted Environmental Concentration
PHS - Priority Hazardous Substance
PCOP - Photochemical ozone potential
Q95 - Freshwater flow equalled or exceeded for 95% of the year
TraC - Transitional and Coastal

Buzz Words & H1 Concepts

H1 Risk Assessment Software and Methodology

The H1 risk assessment is the cornerstone of the UK’s environmental permitting regime for bespoke installations. Using the Environment Agency’s dedicated software, we quantify the impact of a site's activities on air, water, and land. The methodology follows a structured, tiered approach, beginning with basic source-pathway-receptor identification and progressing through complex numerical screening. By inputting process data—such as emission rates and stack heights—the software calculates whether a site’s environmental footprint is "significant." SWEL utilizes this tool to justify permit applications, ensuring that industrial operations are designed with robust environmental safeguards that satisfy regulatory scrutiny.

Environmental Assessment Levels (EAL)

Environmental Assessment Levels (EALs) are the benchmarks used by regulators to judge the acceptability of pollutant concentrations in the ambient air. Each chemical substance is assigned a specific EAL based on its toxicity and potential for long-term or acute harm to human health. In an H1 assessment, we compare your site's Process Contribution (PC) against these levels. If an emission is below 1% of the long-term EAL, it is typically screened out as insignificant. Understanding these thresholds is vital, as exceeding an EAL necessitates either a reduction in emissions at the source or more advanced atmospheric dispersion modeling.

Environmental Quality Standards (EQS)

Environmental Quality Standards (EQS) are legal limits set to protect the aquatic environment, covering discharges to rivers, estuaries, and coastal waters. These standards ensure that hazardous substances do not reach concentrations that would harm fish, invertebrates, or the wider ecosystem. During a H1 water impact assessment, SWEL calculates the "Predicted Environmental Concentration" by considering the upstream background quality and the river's low-flow (Q95) characteristics. If the discharge causes the waterbody to exceed the EQS, or takes up more than 10% of the available "headroom," mitigation or more sophisticated mixing zone modeling becomes mandatory to maintain compliance.

Best Available Techniques (BAT and BATAEL)

Best Available Techniques (BAT) represent the most effective and advanced stage in the development of activities and their methods of operation. Under the Industrial Emissions Directive, operators must demonstrate that they are using BAT to prevent or reduce emissions. BAT-Associated Emission Levels (BATAELs) are the specific numerical ranges provided in BREF documents that define what a "well-performing" plant should achieve. SWEL provides the technical "heavy lifting" required to justify why a specific technology was chosen, ensuring your operation aligns with current BAT conclusions while remaining cost-effective and operationally viable.
Process Contribution (PC) and Predicted Environmental Concentration (PEC)

The H1 screening process relies on two primary metrics: Process Contribution (PC) and Predicted Environmental Concentration (PEC). The PC represents the impact of the site's emissions in isolation. However, the regulator is also concerned with the cumulative effect on the environment. Therefore, we calculate the PEC by adding the PC to the existing "background" concentration of that pollutant in the local area. If the PEC is high—often due to existing heavy industry or traffic—it may "screen in" for further assessment even if the site's individual contribution is relatively small. Accurate PEC calculation is critical for a "duly made" permit application.

VOC and Particulate Emission Screening

Volatile Organic Compounds (VOCs) and Particulates (PM10 and PM2.5) are high-priority pollutants in any industrial risk assessment. VOCs can range from simple solvents to highly carcinogenic substances like Chromium VI, each requiring a specific screening strategy. Particulates are assessed based on their diameter, as smaller particles can penetrate deeper into the lungs. SWEL uses H1 software to screen these emissions by evaluating stack exit velocities, temperatures, and mass release rates. This screening determines if expensive abatement technology, such as thermal oxidizers or bag filters, is required to prevent local air quality standard breaches.

Global Warming Potential (GWP) and Photochemical Ozone Potential (PCOP)

Beyond local toxicity, H1 assessments account for broader "Global Impacts." Global Warming Potential (GWP) measures the climate impact of greenhouse gas emissions (like CO2 or Methane) associated with both direct processes and indirect energy consumption. Photochemical Ozone Potential (PCOP) assesses the potential for a site’s VOC or NOx emissions to react with sunlight and create "ground-level ozone" or smog. SWEL quantifies these impacts to provide a holistic view of a site's environmental performance. This data is increasingly used to satisfy "Net Zero" requirements and corporate social responsibility (CSR) reporting during the planning stage.

AERMOD Detailed Dispersion Modeling Integration

When a pollutant fails to "screen out" in the basic H1 software, detailed atmospheric dispersion modeling using AERMOD becomes necessary. Unlike the simplified H1 tool, AERMOD uses complex mathematical algorithms, local hourly meteorological data, and 3D terrain information to simulate how a plume moves through the air. This provides a much more accurate prediction of concentrations at specific sensitive receptors, such as schools or hospitals. SWEL integrates AERMOD results into the final permit application, often proving that emissions are acceptable in the real world, thereby saving clients from the capital expense of unnecessary abatement upgrades.