Texas Health and Safety Code - HEALTH & SAFETY § 756.001. Covering Large Well or Cistern; Criminal Penalty

(a) The owner or operator of a well or cistern that is at least 10 feet deep and not less than 10 inches nor more than six feet in diameter shall keep it entirely covered at all times except when the owner or operator is actually using the well or cistern.

(b) The cover required by this section must be capable of sustaining at least 200 pounds of weight.

(c) A person commits an offense if the person fails to cover a well or cistern as required by this section. An offense under this subsection is a misdemeanor punishable by a fine of not less than $100 or more than $500.