Abstract: An adjustable-height extension stem and valve box assembly is provided for use with buried valves that is lightweight, readily adjustable to a large range of heights, and is capable of absorbing loads and impacts such that the loads and impacts are substantially not transmitted to the buried valve or surrounding pipeline. The valve box is made up of a valve box base, a valve box lower section, a valve box upper section that telescopes within the lower section, and a valve box top. An upper section of the extension stem extends from the interior of the valve box top through a bottom opening, and an extension stem lower section extends downwardly from the upper section, with the two sections being made from square hollow metal tubing such that the upper section telescopes within the lower section. A grit washer having grooves cut in a bearing surface is attached to the extension stem upper section and supports the upper section in place within the valve box top.