  We consider the linear transport equations driven by an incompressible flow
in dimensions $d\geq 3$. For divergence-free vector fields $u \in L^1_t
W^{1,q}$, the celebrated DiPerna-Lions theory of the renormalized solutions
established the uniqueness of the weak solution in the class $L^\infty_t L^p$
when $\frac{1}{p} + \frac{1}{q} \leq 1$. For such vector fields, we show that
in the regime $\frac{1}{p} + \frac{1}{q} > 1$, weak solutions are not unique in
the class $ L^1_t L^p$. One crucial ingredient in the proof is the use of both
temporal intermittency and oscillation in the convex integration scheme.
