  Exact solutions for Shapovalov wave spacetimes of type I in the scalar-tensor
theory of gravity of Brans-Dicke are constructed. Shapovalov's wave spacetimes
describe gravitational-wave models that allow the separation of wave variables
in privileged coordinate systems. In contrast to the general theory of
relativity, the vacuum field equations of the Brans-Dicke scalar-tensor theory
of gravity lead to exact solutions for type I Shapovalov spaces, which makes it
possible to construct observational checks for detecting such wave
disturbances. For the models under consideration, equations for the
trajectories of test particles are obtained.
