EPA Tanks 4.09d: Challenges and Modern Alternatives

EPA Tanks 4.09d: Shortcomings and Modern Alternatives for Accurate Storage Tank Emission Calculations

For years, EPA Tanks 4.09d (commonly referred to as Tanks 4) was the standard desktop software used to estimate volatile organic compound (VOC) and hazardous air pollutant (HAP) emissions from storage tanks. It was widely adopted by facilities and consultants to help meet EPA and state air quality compliance requirements.

The program could estimate emissions for multiple tank configurations, including:

- Vertical and horizontal fixed-roof tanks
- Internal and external floating-roof tanks
- Domed external floating-roof tanks
- Underground tanks

However, the EPA has officially discontinued support for Tanks 4.09d, acknowledging that it no longer aligns with current regulatory methodologies or data accuracy needs. This has created a growing need for modern, accurate, and user-friendly alternatives to ensure ongoing compliance and reliable emissions estimation.

The Limitations of EPA Tanks 4.09d

Although it served the industry for decades, Tanks 4.09d contained several critical shortcomings that often led to inaccurate VOC and HAP emissions results. Below are some of the key issues that users and regulators have long recognized.

1. Oversimplified Bulk Temperature Calculations
Tanks 4.09d used the average annual ambient temperature of a tank’s location to estimate the liquid bulk temperature for non-heated tanks. This method ignored monthly temperature variations, leading to over- or under-estimations of emissions — particularly when calculating monthly totals.

2. Temperature Limitations for Heated Tanks
The software capped vapor pressure interpolation at 100°F, even though many heated tanks operate above this temperature. As a result, vapor pressure and emission estimates were understated for tanks running hotter than 100°F.

3. Unrealistic Full-Insulation Assumptions
Tanks 4.09d assumed that all heated tanks were fully insulated, which set standing losses to zero by default. In reality, partial insulation or uninsulated roofs lead to measurable standing losses — which the program failed to capture.

4. Missing Parameters for Floating Roof Tanks
The tool lacked an option to indicate whether the liquid in a floating roof tank was heated or not. This omission caused misleading emission results when calculating losses for heated floating tanks.

5. No Calculations for Roof Landing or Tank Cleaning
Tanks 4.09d did not include features to calculate emissions from roof landings or tank cleanings, which can contribute significantly to total annual VOC and HAP emissions.

In short, while the software provided a useful foundation, it is now considered technically outdated, inaccurate, and incomplete for today’s compliance and reporting standards.

A Modern Alternative: DREEM Solutions

Recognizing these industry challenges, DREEM Solutions has developed a powerful and accurate alternative to EPA Tanks 4.09d. Our cloud-based storage tank emissions software is built to provide high-precision VOC and HAP calculations using EPA AP-42 Chapter 7 equations — with modern functionality and automation that today’s facilities need.

Why Choose DREEM Solutions
✅ Accurate monthly and annual emissions based on AP-42 Chapter 7
✅ Ability to calculate partial-month emissions (for mid-month stock changes)
✅ 12-month rolling totals and averages for throughput and emissions
✅ Process multiple tanks at once — no need to calculate individually
✅ Customizable reports that align with EPA or state agency formats
✅ Integrated business intelligence module for source-by-source comparison
✅ Built-in compliance checks against permit limits
✅ Group tanks by permit category or physical location for easier management

With DREEM, you can move away from spreadsheets and outdated desktop tools — and instead use a modern, web-based platform that provides real-time visibility, automated reporting, and compliance confidence.

Beyond Tanks: A Complete Environmental Data Management Solution

DREEM Solutions goes beyond storage tanks. Our platform provides a centralized system to manage all of your environmental and sustainability data — including air emissions, greenhouse gases, water, and waste.
With automated calculations, record-keeping, and audit-ready reports, DREEM helps your organization maintain compliance, reduce risk, and save time across all environmental reporting areas.

Request a Demo

If your facility or consulting team is still relying on EPA Tanks 4.09d, now is the time to upgrade.
Experience a smarter, faster, and more reliable way to manage storage tank emissions with DREEM Solutions.

Contact us today to request a demo and see how our platform can replace Tanks 4.09d with a more accurate, flexible, and compliant solution for your emission calculations.