Every building moves two kinds of water out of the property. One is wastewater from toilets, showers, kitchens and laundry. The other is rain from roofs, driveways and gardens. In Costa Rica both have their own rules and their own permits, and mixing them up is one of the most common causes of overflowing septic systems, failing treatment plants and complaints from neighbors.
Ingeniería de las Aguas designs and builds sanitary sewer networks, sewer connections, storm drainage and drain fields for residential, commercial, industrial and urban projects, and we handle the related permits.
Sanitary sewer networks
Residential developments, condominiums, hotels and commercial centers need an internal network that collects wastewater from every unit and carries it to a treatment plant or to the public sewer. A good network is invisible. A bad one shows up as blockages, odors and manholes that overflow in the rain.
What we look after in a design:
- Slopes and depths that keep the flow moving without digging trenches deeper than they need to be.
- Manholes and cleanouts where crews can actually reach them.
- Pipe materials and joints that keep groundwater out. In coastal areas with a high water table, leaky pipes let groundwater in and can overload the plant downstream.
- Grease control at restaurants and kitchens, with properly sized grease traps.
- Pumping where the land is too flat or the levels do not work by gravity. See pumping stations.
- Phasing, so a development built in stages can grow without rebuilding the first phase.
Connecting to a public sewer
A public sewer is the simplest destination for wastewater when one exists. In Costa Rica it is usually operated by AyA, the national water and sewer institute, or by the municipality, and coverage is limited: many cantons and most beach towns have none.
When a sewer is available:
- The operator must accept the volume and quality of the wastewater. For a project that is not exempt from operational reports, a letter of availability from the operator is needed for the health operating permit.
- Discharges to the sewer must meet the limits of the Wastewater Discharge and Reuse Regulation, Decree 33601-MINAE-S. For example, 300 mg/L of BOD, 750 mg/L of COD, 300 mg/L of suspended solids and 50 mg/L of fats and oils. These limits are looser than for discharge to a river, but they still matter for restaurants and industry.
- Single-family homes are exempt from operational reports. So are activities listed in Annex 1 of the regulation that discharge only domestic wastewater to the sewer. Others that discharge only domestic wastewater can ask the sewer operator for an exemption.
When there is no sewer, Decree 39887-S-MINAE, the regulation for approving treatment systems, requires the treated water to have another approved destination: discharge to a river or creek with a permit, reuse, infiltration into the ground, evaporation or a combination. That is the job of a treatment plant or, for a house, an improved septic system.
Drain fields
Where treated water goes into the ground, the drain field is part of the drainage system and often the weakest link. Decree 42075-S-MINAE only accepts infiltration trenches, sized from a percolation test, with the water table at least 1.5 m below the bottom of the trench and slopes no steeper than 30 %. Seepage pits are banned. We design and build drain fields to those rules and fix fields that have failed; our guide on septic smells and overflows explains the usual causes.
Storm drainage
Rain in Costa Rica arrives in quantity. According to the National Meteorological Institute (IMN), the Pacific rainy season runs from May to October, with November as a transition and the heaviest rain in September and October. The Caribbean side has no well-defined dry season at all. A project needs a storm system that:
- Keeps rainwater out of septic tanks, plants and drain fields. Rain entering the wastewater system dilutes it, overloads it and pushes sludge out with the treated water. Decree 42075 also bans sending septic effluent to the storm sewer, so the two systems must stay separate in both directions.
- Protects drain fields from runoff coming downhill.
- Discharges where the municipality allows, at a rate that does not flood the street or the neighbors. Most municipalities review a project's stormwater outlet before issuing the building permit, and larger developments are usually asked for a hydrological study. Requirements vary by canton.
- Handles erosion on slopes, which is critical on hillside lots in the Central Pacific, the Southern Zone and the Central Valley.
Permits and coordination
Sewers and drainage touch several agencies: the Ministry of Health for wastewater systems, AyA or the municipality for sewer connections, the municipality for stormwater and building permits, and, for larger projects, SETENA, the National Environmental Technical Secretariat, for environmental approval. We prepare the designs and filings; see our permits service. We also work on public infrastructure; see public works.
Where we work
We serve Western Alajuela, the Greater Metropolitan Area, Guanacaste, Puntarenas (Central Pacific and Southern Zone) and Limón. See areas we serve.
Talk to us
Send us a message on WhatsApp with the project location, a site plan if you have one, and what you need: a new network, a sewer connection, storm drainage or a fix for a system that floods. You can also use our contact page.