This buried infiltration basin was installed in 2026 at Moisenay (77950), Seine-et-Marne, as part of the servicing works for a 17-lot housing development.
The structure, built using OPTIBOX modules, achieves a useful storage volume of 41 m³ in a single layer — overall structure depth: 0.66 m — over a footprint of 27 m × 2.4 m (64.8 m²).
Stormwater is discharged by infiltration into the ground, with flow regulated at 1 l/s. The structure is overlaid by a single-lane access road serving the development.
2026
Year of installation
41 m3
Storage capacity
Road
Type of overburden
Project context — stormwater management for a new housing site
As part of the servicing works at Moisenay, the design engineer specified a buried infiltration basin to manage stormwater runoff from the roofs and roads of the new residential scheme.
The primary constraint: installing the structure within a very narrow, linear footprint — entirely beneath a single-lane access road. This configuration, typical of peri-urban housing developments, requires a low-profile storage module capable of sustaining vehicular (VL) loading while maintaining adequate storage volume.
The OPTIBOX, with its 0.66 m single-layer structure depth and short-term vertical compression resistance exceeding 420 kPa (NF EN 17150), was the precise response to these requirements.
Technical data — a flow-regulated infiltration basin
The structure operates as an infiltration basin with a flow regulator set at 1 l/s, controlling discharge to the downstream network during storm events. The adopted layout delivers a total useful volume of 40.7 m³.
Layout and geometry
The linear site constraint led to a basin geometry of 27 m × 2.4 m, single layer, giving a structure depth of 0.66 m. This elongated layout — suited to the narrow strip of land along the roadway — demonstrates OPTIBOX’s ability to conform to atypical footprints that bulkier solutions cannot accommodate.
The structure is wrapped on all faces in a 300 g/m² geotextile, preventing fine soil particles from migrating into the structure and maintaining permeability throughout its service life.
Technical characteristics of the installed product
Module dimensions:
1,200 x 600 mm.
Module depth:
660 mm.
Storage capacity:
≥ 95 %.
Material:
Recycled polypropylene — recyclable
Optibox
The Optibox system, with a 95% void ratio, represents a new generation of SAUL units with three-dimensional diffusion. It provides temporary stormwater storage and enables the construction of underground public or private structures that can be inspected and easily hydro-cleaned.
View product sheetSite programme
For any underground structure project, our Design & Sizing team provides the technical drawings and layout plan tailored to your scheme.
1. Excavation and preparation
Works took place on a plot to the west of the development, bounded by a historic stone wall (to be demolished in a subsequent phase to create vehicular access). The excavation was carried out to the basin width, with a 0.50 m working margin around the perimeter, in accordance with OPTIBOX installation requirements.
2. Geotextile and module installation
A bedding layer and 300 g/m² geotextile were laid in the base of the excavation before module installation. The OPTIBOX half-modules were then positioned layer by layer, following the layout plan provided by the Nidaplast technical team. No tools are required: the integrated self-locking system allows modules to be clipped together by hand, significantly reducing installation time in this confined trench.
Integrated handling grips on each half-module simplified individual piece handling, even at the base of a narrow excavation.
3. Basin closure and hydraulic connections
OPTIBOX peripheral panels closed the structure on all faces. Two inspection manholes were connected upstream and downstream, including the 1 l/s flow regulator at the outlet. The geotextile was then folded back over the top face of the modules before backfilling.
4. Overburden — beneath a single-lane road
The structure is overlaid by a single-lane road surface serving all 17 plots.
The OPTIBOX permanent admissible load (>40 kPa long-term, safety factor ×2 extrapolated to 50 years) and maximum overburden depth of 2 m comfortably meet the requirements of a residential VL road.
Key points noted by the design engineer
Geometric adaptability — the 27 m × 2.4 m linear layout demonstrates that OPTIBOX can occupy footprints that large-format modules cannot.
Installation speed — the absence of clips or specialist tooling allowed a standard VRD crew to install the structure without dedicated training.
Road-compatible loading — the module’s mechanical resistance (>420 kPa short-term) is rated for VL traffic loads, including compaction of overburden layers.
Design traceability — Nidaplast’s layout study gives the design engineer and VRD contractor a precise installation plan, a reference cross-section, and a complete materials schedule from tender stage.
NIDAPLAST CASE STUDY — OPTIBOX
Project: Buried infiltration basin — SAUL 3D diffusion type — under access road
Scheme: 17-lot housing development — Moisenay (77950), Seine-et-Marne, France
Product: OPTIBOX Nidaplast — 3D diffusion underground stormwater module
Basin type: Infiltration basin with regulated outflow (1 l/s)
Useful volume: 40.7 m³ — Footprint: 27 m × 2.4 m — Area: 64.8 m²
Number of layers: 1 — Structure depth: 0.66 m
Modules installed: 181 OPTIBOX half-modules + 99 peripheral panels
Geotextile: 203 m² at 300 g/m²
Context: Narrow linear footprint, overburden beneath single-lane VL road
Key feature: Tool-free assembly, integrated self-locking system
Manufacturer: Nidaplast — Fresnes-sur-Escaut, Hauts-de-France, France
Standards: NF EN 17150 — Compression resistance >420 kPa (short-term)
SuDS relevance: Infiltration basin — complies with Building Regulations Part S / CIRIA C753 principles
