Cargo Port & Marine Drainage

Two waterfronts, one shoreline

A container terminal, bulk wharf or ro-ro berth needs drainage coordinated with cargo operations, heavy equipment and the quay structure. A marina or boatyard combines trailer parking, travel-lift routes, hull storage, pedestrian decks, fueling and vessel cleaning. These zones can share an outfall while requiring different collection systems and separate waste streams.

Waterfront design starts with surveyed pavement and outlet elevations, actual wheel loads and the exposure zone. Flat terrain limits available fall; tidal or lake water levels can restrict discharge; salt deposits and wet crevices can attack exposed hardware. A channel cannot correct adverse pavement grades or prevent coastal inundation. Identify whether flooding starts at a blocked inlet, a settled slab, an undersized connection or the receiving water before replacing the drain.

How water moves on a wharf, an apron and a boatyard

Survey the apron crossfall, settled slabs, wheel ruts, roof discharge points and the water levels at each outfall. Use linear interception where sheet flow crosses an entrance or approaches a protected boundary; use point inlets where pavement can drain reliably to discrete low points. Either layout can fail after settlement. Regrading, additional outlets or pavement repair may be more effective than adding a longer channel. In a boatyard, map runoff around hulls and stands, then intercept sediment-bearing flow at useful collection points such as gravel-to-pavement transitions.

Interception first, low-point collection second

Interception collects water across its path, for example above a launch ramp or ahead of a building entrance. Low-point collection uses an inlet where grades converge. Combine them when helpful; an accessible channel outlet or in-line sump may provide maintenance access without a separate square basin. Locate access where parked containers, blocked boats and stored equipment will not cover it.

Run the volume before you pick a width

One inch of rain on 1,000 square feet is about 623 gallons before infiltration and other losses. On two acres (87,120 sq ft), that is about 54,300 gallons; on a 12,000 sq ft lot it is about 7,480 gallons. For an illustrative small-catchment Rational Method calculation, Q ≈ C × i × A in cubic feet per second, with intensity in inches per hour and area in acres. At C = 0.95 and i = 1 in/hr, two acres yield about 1.9 cfs, or 850 gpm. Use locally adopted rainfall intensity for the selected recurrence interval and time of concentration, plus any roof contributions. These examples are not a coastal design storm. Our Runoff Calculator and runoff guide help organize the inputs; storage needs a storm hydrograph and discharge assessment.

Check the inlet, channel, and discharge route

Check inlet capture and bypass, channel conveyance, outlet connections, pipe capacity and downstream water level together. For illustration, full circular pipes with actual internal diameters of 6, 8 and 12 inches, Manning’s n = 0.010 and energy slope = 1% convey about 330, 705 and 2,080 gpm. This idealized calculation excludes entrance, bend, junction and valve losses. Two 6-inch pipes provide only about one-third of one 12-inch pipe’s flow under these assumptions. Specify actual material, internal diameter and roughness; a wide channel ending at a small connection can surcharge even when clean.

A submerged outlet can still discharge when upstream head exceeds tailwater and losses. Its invert being below high tide does not by itself prove that the whole network floods. Calculate the hydraulic grade line using the design receiving-water levels, including the project’s tide, surge or lake-level scenarios and future conditions. Set acceptable ponding and a safe exceedance route. A backflow valve blocks reverse flow but needs head to open and adds resistance; storage or pumping may be needed while gravity discharge is restricted. Pump-dependent systems also need access, alarms and a power-failure operating plan.

Hydraulic examples are screening estimates, not rated system capacities. Check actual internal diameter, roughness, design head, losses, and tailwater using the FHWA drainage design method and the selected manufacturer’s data.

Coordinate collection with the waterfront drainage design

Select the collection hardware within the complete drainage package. Drainage Connect’s listed channels, basins, fittings and separators cover parts of that package; outfall structures, pumps and treatment beyond the listed range may require specialist suppliers. Confirm the exact scope and availability before ordering.

• Surface interception and collection — trench drains, catch basins, grated inlets, grates, frames. Confirm capture performance as well as loading.
• Small-diameter conveyance — PVC, drainage fittings and cleanouts. Pop-up emitters and dry wells need a suitable, approved inland discharge location; neither is a default solution in a saturated or contaminated waterfront yard.
• Trunk storm mains and outfall structures — large-diameter HDPE or RCP, headwalls, wharf penetrations. By others.
• Tidal backflow protection — flap gates, duckbill valves, tide gates. Specialist outfall equipment. Our PVC swing check listings cover small piping; select any branch or pump-discharge valve for its orientation, pressure, temperature and fluid limits. An outside option such as Red Valve Tideflex addresses stormwater and tidal backflow. Compare its opening head, headloss, elastomer compatibility, debris clearance and inspection access with a suitable flap gate; a small plumbing check valve is not an outfall substitute.
• Oil-bearing runoff may need separation and controlled discharge. Drainage Connect lists ACO Oleopator and Spill Control oil-water separators; select a model from the actual flow, oil, solids and cleaning chemistry. Review an ACO oil-water separator. Manufacturer separation guidance describes the product range. A separator does not make every waste stream acceptable for discharge or replace engineered treatment. The project designer must coordinate any required containment, pumping, pretreatment, approvals and maintenance, with equipment availability confirmed for the specified package.

In the US, determine the applicable industrial stormwater permit from the facility’s activities and permitting authority. EPA Sector Q and Sector R guidance distinguishes transportation facilities with maintenance or cleaning from ship and boat building or repair yards. Many states issue their own permits; EPA’s MSGP does not automatically cover every marina. Follow the applicable permit’s SWPPP, monitoring and maintenance requirements.

Load class: start with the equipment and installation

Use the project’s required standard and actual equipment loading to select a documented channel assembly. EN 1433 uses the following test-load classes; the terminal label alone does not establish the required class.

• EN 1433 A15 — 15 kN test force. Areas used only by pedestrians and cyclists.
• EN 1433 B125 — 125 kN test force. Pedestrian areas, car parks and parking decks; verify the product and traffic.
• EN 1433 C250 — 250 kN test force. Kerb and edge-of-road locations; not a blanket truck-aisle or forklift specification.
• EN 1433 D400 — 400 kN test force. Road traffic lanes and parking areas, subject to the selected assembly and installation.
• EN 1433 E600 — 600 kN test force. Locations with high wheel loads, with project-specific design and manufacturer confirmation.
• EN 1433 F900 — 900 kN test force. Locations with exceptionally high wheel loads, with project-specific design and manufacturer confirmation.

EN 1433 class numbers state a test force in kilonewtons, not a permissible vehicle weight. NDS letter classes use separate pressure and traffic recommendations; NDS Class B does not establish EN 1433 B125. H-20, HS-25 and AASHTO M306 also require their own applicable documentation. Do not use a letter match, PSI conversion or an EN-to-AASHTO shortcut as evidence of compliance. See the load recommendation guide.

Specify the channel, grate, edge rail, locking hardware and installation detail together. Concrete surround, reinforcement, joints and support depend on the assembly, traffic and pavement structure; “full encasement” is not one universal detail. Check concentrated loads from trailer legs, outriggers and boat stands separately and keep them off drains unless explicitly approved. On suspended wharf decks, verify structural capacity, waterproofing and penetrations before cutting a trench.

Salt is the second design load

ACO polymer-concrete, Josam Pro-Plus SMC/GRP, and BG Filcoten high-performance concrete are different channel constructions. Choose the body, grate, frame and fasteners for the coastal exposure and traffic; Josam identifies Pro-Plus as sheet-molded glass-reinforced polyester, not polymer concrete.

Do not make stainless rails the default solely because spray reaches the drain. ACO identifies KS100 rails as grade 304 stainless; that is not a universal seawater specification. Compare approved alloys or other constructions for wetting, chloride concentration, temperature, deposits and cleaning chemicals. ACO’s stainless resistance table is a screening aid, not approval for every mixture. Confirm seals, coatings and joints as well as the body, grate and frame. Use manufacturer-approved fastener combinations and isolation where needed; wet dissimilar-metal contact requires review, but replacing specified hardware arbitrarily can compromise the assembly.

Where the water is, zone by zone

• Operational apron and hardstand. Compare linear channels with point inlets and engineered trench-and-frame systems. Select width, depth, slope and outlet spacing from capture and conveyance calculations. Reach stackers and straddle carriers require actual loaded wheel forces, tire characteristics and turning movements; E600 or F900 may be appropriate, but neither follows automatically from the location.
• Gate lanes, chassis yards and rail crossings. Account for truck, yard tractor and maintenance traffic, plus dunnage, banding and gravel. Keep trailer support legs away from the run. Use accessible solids collection and a grate that balances capture, debris passage and pedestrian needs. Rail interfaces require coordination with the railway owner; see rail and transit drainage.
• Travel-lift piers, slipways and launch ramps. Keep channels outside lift wheel paths where practical; approved crossings need the loaded wheel and support details. Intercept clean upland runoff above a ramp when grades permit. Do not route vessel wash water onto the ramp or assume a ramp-top trench controls tidal inundation.
• Wash racks, bottom-paint pads and fuel docks. Separate wash water, paint debris, oily water and sewage from ordinary runoff. Curbs or graded containment, sealed joints and collection to an approved treatment, recycling or disposal route may be needed. EPA’s Sector Q fact sheet excludes vessel pressure-wash water, bilge water and sanitary waste from industrial stormwater coverage. An oil separator is not blanket treatment for antifouling metals, detergents or emulsified oil; EPA explains the limits of oil/grit separation. Confirm any sewer connection with the receiving utility; keep sewage pump-out separate. Compare fleet and truck wash drainage.
• Marina parking, drive aisles and yard entrances. Use surveyed flow paths to locate interception lines and catch basins. Choose sump volume below the outlet from sediment loading and practical cleaning frequency, not nominal basin width. A 12-inch, 18-inch or 24-inch basin still needs a suitable outlet, frame and installation for traffic.
• Clubhouse hardscape, pool decks and gangway landings. On accessible walking surfaces, ADA 302.3 limits openings so a sphere over 1/2 inch cannot pass; elongated openings have their long dimension perpendicular to dominant travel. That rule alone does not prove heel, barefoot or small-caster suitability. Check surface stability, slip resistance and changes in level. Pool deck drainage is separate from pool circulation and backwash; see resort and hospitality drainage.
• Roofs and covered work areas. Keep cleaner roof runoff out of contained wash-water systems where the approved design permits. Roof drains, leaders and emergency overflow require their own sizing; include roof flow in downstream capacity wherever it joins the site network.

Compare the listed systems against the job