The Lagoon aka Ala Wai Canal was a by-product
In Pinkhams February 21, 1906 report to the Board of Health I found this on page 1….
Section 1025 Revised Laws of the Territory of Hawaii mandates:
“Whenever in the opinion of the Board of Health any tract or parcel of land situated in the District of Honolulu, Island of Oahu, shall be deleterious to the public health in consequence of being low, and at times covered or partly covered by water, or of being situated between high or low water mark, or of being improperly drained or incapable by reasonable expenditure of effectual drainage, or for other reason in an unsanitary or dangerous condition, it shall be the duty of the Board of Health to report such fact to the Superintendent of Public Works together with a brief recommendation of the operation deemed advisable to improve such land.”
Further down on page 1: “The President of the Board of Health (Pinkham) recommends that the Government , by its right of eminent domain, shall in an equitable and just manner acquire such ownership and rights in said district as shall enable it to transform it into an absolute sanitary, beautiful and unique district. One that will add immensely to the reputation of Honolulu at home and abroad.”
Soil was needed to fill in the duck ponds, rice paddies and banana patches of Waikiki.
Page 7: “In order to secure filling material a great lagoon would as a consequence be formed.”