With financing, plans, engineers and manpower in hand, Hind was ready to proceed. Work commenced in January of 1905.

Excerpts from O’Shaugnessey’s 1906 article, Irrigation Works in the Hawaiian Islands, provide a glimpse — in the words of chief engineer O’Shaugnessy himself — at the scope and class of the work, as well as the spirit and resolve of the workmen:

The work was conducted under the greatest difficulties, as almost continuous rains were experienced from April to July, during all of which the trails had to be made and materials transported and shelter and buildings made for housing 600 Japanese laborers. Those men seemed to like this class of work and made a success of breaking rock where other nationalities were a failure. As their wages average only $1 per day for the ordinary classes of lava rock encountered, hand drilling with Japanese is more economical than the use of either air or electric drills.

In the 14 miles there were: 45 tunnels, aggregating 46,000 feet; 20 flumes, aggregating 2,000 feet; ditching, 23,000 feet; Total – 14 miles or 71,000 feet. The longest tunnel was 2,500 feet, and was cut through in 10 months, being completed on March 24, 1906.

A hospital and medical department was provided for the men, who were assessed 50 cents per month apiece for this object. The Japanese are indifferent to weather conditions, rain and exposure seeming to keep them in a healthy condition, while white men, similarly exposed, would be disabled by rheumatism and other ailments.

The crews lived in ramshackle camps scattered around the mountain valleys. Their buildings were generally constructed with tree fern logs for floors and light wooden framework which was covered with tar paper to form walls and roofs. They lived and worked in a region where 150 inches (i.e., over 12 feet) of annual rainfall is normal and flat land is still steep. Often these camp sites were carved from solid rock and were subject to destruction from falling boulders.

Tunnel work largely consisted of hand drilling, setting charges, blasting and removal of the rock fragments by way of hand loaded railway carts. Locomotion was human muscle. Tunnel builders often experienced “powder consumption” caused by fumes released by burning nitro-glycerin. Symptoms included muscular rheumatism and great bodily emaciation.

Seventeen lives were lost; a life for each mile, a life for each month. Several men fell off the trails while they were being built, a number died from uncontrolled dynamite explosions. One fell into a pump chamber and broke his neck and another was jammed between a boat (used in transporting material) and the sides of the tunnel.

Working 24 hours a day, in multiple tunnels simultaneously, the work was completed on schedule in 18 months. Actual cost was slightly over the original $600,000 budget at $694,231 (equivalent to roughly $18.3 million in today’s dollars).