§ 25-8-213. WATER QUALITY CONTROL STANDARDS.

(A)

A water quality control must be designed in accordance with the Environmental Criteria Manual.

(1)

The control must provide at least the treatment level of a sedimentation/filtration system under the Environmental Criteria Manual.

(2)

An impervious liner is required in an area where there is surface runoff to groundwater conductivity. If a liner is required and controls are located in series, liners are not required for the second or later in the series following sedimentation, extended detention, or sedimentation/filtration.

(3)

The control must be accessible for maintenance and inspection as prescribed in the Environmental Criteria Manual.

(B)

A water quality control must capture and treat the water draining to the control from the contributing area. The required capture volume is:

(1)

the first one-half inch of runoff; and

(2)

for each 10 percent increase in impervious cover over 20 percent of gross site area, an additional one-tenth of an inch of runoff.

(C)

The location of a water quality control:

(1)

must avoid recharge features to the greatest extent possible;

(2)

must be shown on the slope map, preliminary plan, site plan, or subdivision construction plan, as applicable; and

(3)

in a water supply rural watershed, may not be in the 40 percent buffer zone, unless the control disturbs less than 50% of the buffer, and is located to maximize overland flow and recharge in the undisturbed remainder of the 40 percent buffer zone.

(D)

This subsection provides additional requirements for the Barton Springs Zone.

(1)

Approval by the Watershed Protection Department is required for a proposed water quality control that is not described in the Environmental Criteria Manual. The applicant must substantiate the pollutant removal efficiency of the proposed control with published literature or a verifiable engineering study.

(2)

Water quality controls must be placed in sequence if necessary to remove the required amount of pollutant. The sequence of controls must be:

(a)

based on the Environmental Criteria Manual or generally accepted engineering principles; and

(b)

designed to minimize maintenance requirements.

Source: Sections 13-7-18, 13-7-19, and 13-7-34; Ord. 990225-70; Ord. 010329-18; Ord. 031211-11; Ord. 20131017-046.