Langan International curacao Eastpoint projects Stormwater, Rainwater Harvesting. Rainwater harvesting (collection and storage of rainfall) for non-potable uses is a potential sustainable practice that can be considered. Rainwater harvesting can result in a reduced demand on the central potable water distribution system.

Langan International curacao Eastpoint projects Stormwater, Rainwater Harvesting.

Rainwater harvesting (collection and storage of rainfall) for non-potable uses is a potential sustainable practice that can be considered. Rainwater harvesting can result in a reduced demand on the central potable water distribution system.


Rainwater Harvesting:

Rainwater harvesting (collection and storage of rainfall) for non-potable uses is a potential sustainable practice that can be considered. Rainwater harvesting can result in a reduced demand on the central potable water distribution system.
Below, we provide a sample calculation to show the potential savings on public water facilities that rainwater reuse can provide when implemented on a widespread basis.

Our calculations are based on assumed roof-top areas for single family homes in low density parcels and high density uses such as hotel or other common use parcels such as a golf clubhouse. Our assumptions can then be adjusted once specific building footprints are established by the future development project engineers and the calculations can be revised fairly easily at that time to yield
more accurate potential volumes.

Rainwater Reuse Calculations:
Rainwater can be collected locally from individual homes and larger buildings, using individual cisterns and products such as those included in Appendix D.

Individual Homes:

If we assume a typical single family home structure to have a building footprint of 100 square meters (sm) and we assume that annual rainfall is equivalent to 570 mm, then we can estimate a potential rainwater volume that can be captured and re-used by each home to be:

􀁸 100 sm x 570 mm / (1,000 mm/m) = 57 cubic meters (cm)

Since during rainy periods, greater amounts of rainfall will occur then can be reasonably stored, we can consider a 50% capture rate, which would result in 28.5 cm of rainfall available for capture, storage and reuse by each home.

If we assume that 1 cm/day (264 gallons per day) is needed to irrigate a typical single family home property, then potentially 28.5 days per year of irrigation supply could be realized and reduced from the total annual potable supply systems. Considered for a total project build out of 10,000 homes, about 28,500 cm (10,000 homes x 28.5 cm) could be saved from the annual potable water supply budget.

Larger Buildings:

Similarly, larger buildings, such as hotels, a beach club or a golf
clubhouse could also yield rainwater volumes that can be captured from the roof into cisterns for future use in non-potable applications.

If we assume a building footprint of 1,000 sm, then the resulting
potential volume that can be stored at a 50% capture rate would be:
􀁸 1,000 sm x 570 mm / (1,000 mm/m) = 570 cubic meters (cm) or 285 cm (at a 50% capture rate) per building

Porous Pavements:

Whenever possible, porous pavements could be encouraged. Porous or 􀁱pervious􀁲 pavements allow stormwater runoff to infiltrate back into the ground. Infiltration of stormwater provides two distinct environmental benefits. First, runoff rates and volumes can be reduced thus reducing flooding occurrences.

Second, infiltration helps recharge groundwater supplies. Groundwater supplies get depleted when they are excessively extracted through wells and when they are excessively covered with impervious development such as buildings and roads. Depleted groundwater supplies are then no longer available for potable water extraction and in some instances they are can negatively affect vegetative and animal life in the ecosystem. 

The phrase 􀁱porous pavements􀁲 is an umbrella term for porous pavers, lattice pavers (also known as grassed pavers), porous concrete, and porous asphalt. Generally, this BMP allows stormwater to penetrate the respective surface material and flow directly into an underlying stone bed. The stone bed serves as a reservoir allowing the stormwater to be attenuated until infiltrating and recharging the groundwater.

Benefits of Porous Pavements:

􀁸 Research has concluded that approximately 97% of oils
introduced into pervious pavements are trapped and biodegraded.
􀁸 Visual awareness of the BMP for public.
􀁸 Improves the health of surrounding landscape compared
to traditional pavement.
􀁸 Eliminates 􀁱bird baths􀁲 in parking lots.
􀁸 Contributes to groundwater recharge.
􀁸 Overall reduction in runoff volume; this reduction can
contribute to a relatively smaller stormwater pond.
􀁸 TSS (Total Suspended Solids) Removal can be as high as
80% in optimal conditions

Stormwater Capture and Re-use:

Where stormwater runoff is determined to simply run and discharge to the sea or discharge to an area that does not benefit from its contribution, the best practice can be to capture the stormwater and re-use it for other purposes such as lake replenishment and irrigation supply water. Other non-potable uses can also benefit from the collection and storage of stormwater runoff.

Cisterns and Rainwater Harvesting Systems:

Cisterns are stormwater storing structures located either above or below ground. The stormwater can be reused in irrigation, or other grey-water applications. The regional precipitation and the catchment area, usually a roof or other impervious surface, are directly proportional to the volume stored in the cistern.

Benefits of Cisterns and Rainwater Harvesting Systems:

􀁸 Reduces yearly cost of potable water and demand on
􀁸 Reduces stormwater runoff.
􀁸 Rainwater is generally soft water and lowers the need for
detergents in laundry.
􀁸 In large cistern cases, potential to sell􀁲 extra􀁲 stormwater
to neighbors for irrigation.

Erosion and Sedimentation Control:

Where stormwater conveyances and discharges exist or are proposed in the future, the conveyance channels should be stabilized with well-established vegetation or rock materials. Stabilized channels protect the underlying soils
from eroding away and resulting in the deposition of sediments at downstream locations or the sea.

Natural Features:

When surface water conveyance systems (ditches and valleys) contribute to natural features such as wetlands and marshes, specific care should be taken to not divert or capture the runoff that contributes to those natural features.

Instead, maintain the future runoff volumes and rates similar to existing runoff volumes and rates so as to not alter these natural features, which can sometimes be considered sensitive eco-systems.
In instances where developed area runoff flows into sensitive wetland or marsh features, water quality improvement methods should be installed prior to the natural discharge point to polish and improve the 􀁱urban􀁲 runoff thereby removing suspended solids and nutrients that the upstream urban development has added to the runoff.

Rain Gardens:
Rain Gardens are planted depressions, either naturally occurring or planned, that are designed to filter stormwater runoff and
improve water quality. Rain gardens can be a stage in a treatment train where stormwater is attenuated prior to being discharged to a larger stormwater management facility.

Benefits of Rain Gardens:

􀁸 Requires less maintenance than lawns. Once garden is
established it will not need to be mowed, fertilized, or
􀁸 Visual awareness of the BMP for public.
􀁸 Creates a wildlife habitat and aesthetically pleasing
􀁸 Contributes to groundwater recharge.
􀁸 Reduces mosquito breeding.
􀁸 Removes a wide range of pollutants such as suspended
solids, nutrients, metals, hydrocarbons, and bacteria.

\\\data\ep\data3\100234301\office data\reports\civil report\2011-05-09 final report\infrastructure
assessment and sustainability report-langan-2011-05-09.doc

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