When ground was broken this week for the $51.3 million Little Dell Dam in Parleys Canyon, it represented something very old, and at the same time something very new.

The "old" is the Little Dell Dam project itself, which has been pursued by Utah for more than a half-century and which was scheduled to begin construction 35 years ago.The "new" is the method of financing adopted by Congress in the 1986 Water Resource Development Act. That law requires significant local sharing of any project cost, instead of the federal government picking up the whole tab.

Under this cost-sharing arrangement, Salt Lake City provided the site for the dam and reservoir; Salt Lake County put up $7.6 million; the Metropolitan Water District of Salt Lake bonded for another $14.3 million, and federal funds provided the balance.

The Little Dell earth-fill dam is the first project approved by Congress under those new guidelines. While this approach is more expensive for local users than the old federal-government-pays-all method, it has its advantages. For one thing, it discourages pork-barrel projects if local entities must raise half the cost.

Construction of the 224-foot-high dam, 1,700-feet long, will commence in 1989 and be finished in late 1991. Water would begin to fill the reservoir in 1992. The U.S. Army Corps of Engineers is doing the work as a flood control measure.

Despite the long delay, Little Dell Dam remains a good investment, both as a source of water and as backup flood control. Salt Lake City's flooded streets would have been spared the 1983 inundation if Little Dell Dam had been in existence then. It's good to see the project finally getting started.