Abstract: An improved lid retainer for a ground-water monitoring well of the type having a housing, a water-tight lid, and a lid fastener for fastening the lid to the housing. The lid retainer has a lid fastener receiving member which cooperates with the lid fastener, a flexible horizontal brace member and a flexible vertical brace member, each connected to the lid fastener receiving member and adapted to be contourable to the shape of the inner surface of the housing of the monitoring well and to provide support therefor. Each brace member has an attachment structure, such as an aperture, for attaching the lid retainer to the housing by suitable fasteners. Preferred fasteners include concrete anchors.