Brentwood Industries
http://www.brentwoodindustries.com/
I began this search by contacting a sales representative in Mexico.
Brentwood tube settler products are produced in Pennsylvania and then shipped to Mexico and constructed in a warehouse. The tube settlers can then be shipped to various locations in Central America.
Product
The hyperlink located bellow leads to a page that has the specifications for the recommended product of interest. They are PVC tube settlers and the recommended size for the Gracias plant is the tubes with a vertical height of 2 ft or 3 ft.
http://www.brentwoodprocess.com/tubesettlers.html
Quoted Price
The quoted price is $220 per square meters of 1 ft vertical height tube settlement module from the construction facility in Mexico.