20 CFR §726.109

1. (a)OWCP may, at its discretion, increase the amount of security a self-insurer is required to post whenever it determines that the amount of security on deposit is insufficient to secure 100 percent of the self-insurer's liability for payment of benefits and medical expenses under the Act. OWCP will provide a written explanation for the increase.
2. (b)OWCP will not require an operator to post greater than 100 percent of its estimated liabilities, based on the information prompting the increase in security.