  We study the impact of very light sterile neutrinos (Delta m^2_new around 1
to 10 times 10^(-2) eV^2, sin^2 2theta_new<10^(-1)) on upcoming theta_13-driven
reactor antineutrino experiments like Double-CHOOZ and Daya Bay. Oscillations
driven by these vales of Delta m^2_new affect data in the near and far
detectors differently and hence potentially modify the capability of these
experimental setups to constrain and measure sin^2 2theta_13. We find that the
hypothesis theta_new different from zero negatively impacts one's ability to
either place an upper bound on sin^2 2theta_13 in the advent of no oscillation
signal or measure sin^2 2theta_13 if a theta_13-driven signal is observed. The
impact of sterile neutrino effects, however, depends significantly on one's
ability to measure the recoil positron energy spectrum. If sin^2 2theta_new is
larger than 10^(-2), upcoming theta_13-driven reactor antineutrino experiments
should be able to measure sin^2 2theta_new and Delta m^2_new, along with sin^2
2theta_13, as long as one is sensitive to distortions in the recoil positron
energy spectrum in the near (and far) detectors.
