Stormwater Plans: What Council Engineers Actually Look For

If you’re preparing a stormwater plan for a Development Application (DA), here’s a reality check from someone who have seen, reviewed and prepared a lot of stormwatear plans. Here are some tips we use at JOCES to make sure a stormwater plan is actually DA-ready, and to avoid going in circles with RFIs 🫡

1. Ensure the Plans are Readable!

First, add notes. Explain your stormwater philosophy and justify your OSD. Additionally, make sure the line types clear between existing and proposed. Another thing we recommend is to annotate everything! This is especially helpful because reviewers don’t have time to guess your intent. The general rule of thumb we follow is to ask ourselves this question: could someone unfamiliar with your design still follow it?

Misinterpretation can lead to delays, and delays often result in increased costs. In short: Misinterpretation = Delay. Delay = $$$.

2. Be Familiar With The Relevant DCP and Engineering Specification.

Next, read the Development Control Plan (DCP) and Design Specs thoroughly. You’d be surprised how often we come across stormwater plans that miss the basics – and one of the most common mistakes is not properly reading and understanding the Council’s DCP and Design Specifications. Engineering standards vary from Council to Council. Don’t assume what’s acceptable, check things like allowable discharge methods and OSD design.

💥 Bonus tip: the low-level property policies/rear lot drainage policies differ wildly between LGAs and can be a trap, so check them early.

3. Justify Everything Such as OSD Exemption and Any Engineering Variation!

If you believe the development is exempt from detention requirements, don’t just leave it out. State it clearly, explain why, and reference the applicable clause in the engineering specification. If your design is includes any engineering variation, explain the variation clearly in your engineering plans or report. Show the performance outcome, the rationale, and tie it to Council objectives.

🎯 Pro tip: Bring it up in a pre-lodgement meeting and prepare a clear justification ahead of time. Know your Council’s variation process and prepare accordingly.

⚠️ Take note: If Council assessors can’t see your reasoning, you might get hit with an RFI.

4. Include Your Modelling as Part of Submission

If you’ve got MUSIC, MUSICX, or DRAINS modelling handy – include them all in your submission. Submitting your modelling files with the DA package shows transparency, and helps Council validate your assumptions and results faster.

5. Owner’s Consent of Downstream Drainage Easement

If the your development site falls to the rear, and you have gone through the long and hard process to negotiate drainage easement over the neighbouring, congrats! That’s a huge win, and it’s usually Council’s preferred discharge option (and rightly so, from an engineering perspective).

But remember, you will need to include owner’s consent from the downstream property to formalise the easement – and it must be part of your DA submission.

6. Provision of Overflow Routes

This one we learnt from another stormwater expert: always ensure there’s an overland flow path for detention basins. There are two key reasons for this: (1) to future-proof the asset under changing climate conditions, and (2) to provide a backup in case of poor maintenance and loss of available basin volume.

7. Clearance and Maintenance Check

Lastly, Design with access and safety in mind. If it can’t be maintained, it probably won’t last. A good stormwater design stands the test of time, and maintenance budget! Keep in mind this question: How much will it cost to maintain this structure? These little tweaks save time and avoids further requests from Council.

At JOCES, we believe good stormwater design is more than just hydraulics— It’s understanding planning frameworks and getting it right the first time. Our expertise in stormwater design and development approval processes has allowed us to work on numerous projects in collaboration with councils, developers, and engineers. By following these guidelines, you can streamline the approval process and avoid common pitfalls.