Service · Infiltration & heavy-rain protection
An infiltration certificate an engineer stands behind.
A calculation is quickly done — but it doesn't take on the responsibility. We plan your infiltration certificate to DWA-A 138-1 and sign off on it: with our name, registration with the Ingenieurkammer-Bau NRW, and insured planning services. Price and turnaround are fixed in writing before you commission us — we often deliver standard cases within a few working days.
- Alvaro Burgos Cifuentes, M.Sc.
- Ingenieurkammer-Bau NRW Nr. 754661
- Insured planning services
- Fixed price
When you need an infiltration certificate.
In NRW, stormwater must be infiltrated locally wherever technically feasible and economically reasonable (§ 44 LWG NRW, § 55 (2) WHG). Infiltration is a use of a body of water that requires a permit — the water authority decides on the basis of the certificate (§ 8 WHG).
New build with an infiltration facility — the certificate is part of the building application documents and a prerequisite for the water-law permit.
More than 800 m² of sealed surface or discharge into a body of water — additionally a certificate for fine suspended solids (AFS63) to DWA-A 102-2.
A sketch or a calculation printout is not enough for the authority — it expects a verifiable design that a chartered engineer signs off on. Anyone who calculates and submits it themselves is personally accountable for it. Anyone who engages us hands that off.
What you receive.
A complete, verifiable package — you submit it directly with the building application:
The result: you submit — and the liability for the sizing sits with us, not with you.
Signed and stamped calculation dossier (PDF, 4–8 pages)
Statement of conformity with the applied standard with DWA-A 138-1
KOSTRA-DWD data extract for your location — every design parameter with a source reference
Dimensioned swale-trench site plan (DWG + PDF)
Authority submission checklist
Certificate for stormwater discharge (AFS63) to DWA-A 102-2 — where relevant
Turnaround time: Standard cases often within a few working days from complete documentation · hybrid systems and special cases correspondingly longer — your deadline is stated bindingly in the quote
Standards: DWA-A 138-1 · DWA-M 102-4 · DWA-A 102-2 · DWA-M 179-1 · KOSTRA-DWD
A typical case
New single-family build in the Heinsberg district, around 240 m² of newly sealed surface. The soil survey is available, the kf-value is within the infiltration range. We size a swale to DWA-A 138-1 using the KOSTRA data for the location and produce the site plan and the statement of conformity with the applied standard — the architect submits the package with the building application. Turnaround: five working days. Fixed price, agreed in advance.
Fixed price. One figure, no hourly risk.
Entry
Plausibility review
Already have a certificate (self-calculated or from a third party)? We review it before the authority does. Written review memo from a chartered engineer.
Standard
Infiltration certificate (concept)
Verifiable design with statement of conformity with the applied standard, ready to submit for the standard case.
Full planning
Infiltration certificate (full)
Incl. dimensioned site plan, variant assessment where necessary, complete authority package.
Add-on
Water balance
Comparison of your property's water regime before and after development (evaporation, infiltration, runoff) to DWA-M 102-4. Required additionally by water authorities depending on the project, particularly for larger projects and in development-plan procedures.
Net prices plus 19% VAT; bracketed figures are gross prices incl. VAT for private clients.
Binding fixed-price proposal for your specific property within 24 hours of the initial consultation. External services (e.g. an infiltration test to DIN 18130, a geotechnical report) are shown separately — no hidden items.
What determines the price and the timeline.
So that a higher quote never looks like bait pricing, we openly name the factors that turn a standard case into a special one:
- Soil permeability (kf-value) — If your soil lies outside the infiltration range (1×10⁻³ to 1×10⁻⁶ m/s), more elaborate solutions are needed — trench systems, hybrid systems or throttled discharge (DWA-A 138-1).
- Surface pollution load (AFS63) — Metal roofs, yards and traffic areas fall into higher load categories and require additional treatment plus the emission verification to DWA-A 102-2.
- Water balance — For development-plan procedures and larger projects, authorities increasingly demand a water balance to DWA-M 102-4.
- Groundwater proximity, water protection zones, contaminated sites — These increase the verification effort — what applies differs by location and municipality.
- External services — Infiltration tests and soil surveys (DIN 18130) are not planning services and are itemised separately — no hidden positions.
Which of these factors apply to your property is what we clarify in the free initial consultation — after that you know price and deadline, bindingly.
Three documents — then the clock starts.
The turnaround time begins as soon as these documents are complete:
- 1
Site plan with the planned building areas and elevations marked
- 2
Geotechnical report with kf-Wert (DIN 18130) and peak groundwater level — if not yet available, we can refer you to suitable geotechnical experts in NRW
- 3
Building application documents or development plan
Three steps to submission.
Initial consultation
30 minutes by video call, free of charge. We clarify the project, the applicable standards, the responsible water authority — and which documents you still need.
Fixed-price proposal
in writing, within 24 hours of the initial consultation. Service, deliverables, turnaround time from complete documentation, one figure.
Calculation & handover
signed off under professional responsibility, with a statement of conformity with the applied standard. You or your architect submit it directly; on request we continue to support the procedure — communication with the authority, responses to queries, coordination of the required investigations (charged by effort).
Frequently asked questions about the infiltration certificate.
How long does the work actually take?
We often handle standard cases within a few working days — counted from the day the site plan and geotechnical report are complete. More complex cases (hybrid systems in poor infiltration conditions, several sub-systems) take correspondingly longer. The turnaround time is stated bindingly in the proposal — before you commission.
What does an infiltration certificate cost?
Concept certificates for standard cases from €700 net (from €833 incl. VAT), full planning from €1,500 net (from €1,785 incl. VAT), each at a fixed price. The exact price depends on the property, the type of facility and the available data — you receive a binding fixed-price proposal within 24 hours of the initial consultation. No hourly billing, no additional charges for the agreed scope of services.
I've already done the calculation myself — can you review it?
Yes, that's exactly what the plausibility review is for (€600): you send us your existing certificate, we check it against DWA-A 138-1 and the water authority's review practice and deliver a written review memo. You stay in control — and know where you stand before submission.
What is a water balance — and do I need one?
The water balance to DWA-M 102-4 compares your property's water regime before and after development: how much water evaporates, infiltrates and runs off — and how close the planned condition stays to the natural one. Whether the authority requires it in addition to the infiltration certificate depends on the project and the municipality; it is typical for larger projects and in development-plan procedures. We clarify whether your project needs one in the free initial consultation — and if so, we deliver it straight away from the same base data.
Who signs off on the planning under professional responsibility?
Alvaro Burgos Cifuentes, M.Sc., registered member of the Ingenieurkammer-Bau NRW (Nr. 754661), with professional indemnity insurance for the planning services. Insurance details: see the About page and legal notice. All calculations and plans are personally reviewed, signed and stamped.
What if the authority has queries or requires additional investigations?
This happens and is not a warning sign: depending on the location, the water authority may, for example, require an infiltration test to DIN 18130 or a supplementary geotechnical report. We tell you already in the initial consultation what to expect at your location based on experience, we formulate the responses to queries and, on request, coordinate the necessary investigations with suitable experts and laboratories — as a separately itemised position, with no hidden costs. That way your procedure keeps moving.
Can you also support the water-authority procedure?
Yes, optionally. The standard service comprises ready-to-submit documents — submission is carried out by the client or the architect. On request we take over direct communication with the responsible water authority, follow-up submissions and queries. This service is charged separately by effort.
In depth
Guide: Infiltration certificate NRW — What the water authority checks in 2026
Free · No obligation · 30 minutes
Who stands behind your certificate?
Send us the site plan and geotechnical report — you receive a binding fixed-price proposal within 24 hours. Or start with a plausibility review of your existing certificate.
- Fixed price, no hidden costs
- Signed off under professional responsibility, insured planning services
- Directly with the engineer