King County and the city of Maple Valley have put into writing their willingness to work together on joint planning for future development of the Summit Pit property, also known as the “donut hole.”

The agreement, announced Thursday, comes on the heels of the county’s announcement that it has a pending deal to sell the land to a developer that wants to build a housing community there.

The formal agreement for joint planning gives the city and the county a voice in major decisions to be made about the 156 acres, which are owned by county but are inside Maple Valley’s city limits.

County Executive Ron Sims has signed a purchase and sale agreement with Yarrow Bay Group for $51 million for the property. The deal is awaiting approval by the County Council.

City officials have expressed concern that they might be excluded from decisions on land-use zoning that would be tied to development.

County Councilman Reagan Dunn, who lives in Maple Valley, congratulated the City Council for its efforts to be involved.

“It was through the perseverance and determination of the city leaders that we were able to get to this agreement,” said Dunn.