Crews could begin moving earth for a 5,000-square-foot retail building and dog park that will be tucked into the landscape of Gateway Lofts at 1719 Grand Ave. in Des Moines (See on map). Construction on the the $700,000 project is expected to take up to six months, according to a letter that was distributed to tenants. Josh Williams of Slingshot Architecture said the project, which has been in planning stages since 2008, took off in earnest earlier this year with an improved economy. The retail building could hold up to three tenants. Beal Derkenne Construction is the contractor. Slingshot is the designer. Striggles Legacy LLC of Oklahoma is the owner.