2020 MS4 General Permit Section 23 Alum or Ferric Chloride Phosphorus Treatment Systems 2020 MS4 General Permit Section 23 Alum or Ferric Chloride Phosphorus Treatment Systems

Section 23 Alum or Ferric Chloride Phosphorus Treatment Systems

23.1

Alum or Ferric Chloride Phosphorus Treatment Systems. [Minn. R. 7090]

23.2

If the permittee uses an alum or ferric chloride phosphorus treatment systems, the permittee must comply with Section 23 requirements. [Minn. R. 7090]

23.3

The permittee's alum or ferric chloride phosphorus treatment systems must comply with the following:

a. the permittee must use the treatment system for the treatment of phosphorus in stormwater. Non-stormwater discharges must not be treated by this system;

b. the treatment system must be contained within the conveyances and structural stormwater BMPs of the MS4. The utilized conveyances and structural stormwater BMPs must not include any receiving waters;

c. phosphorus treatment systems utilizing chemicals other than alum or ferric chloride must receive written approval from the Agency; and

d. in-lake phosphorus treatment activities are not authorized under the General Permit. [Minn. R. 7090]

23.4

The permittee's alum or ferric chloride phosphorus treatment systems must meet the following design parameters:

a. the treatment system must be constructed in a manner that diverts the stormwater flow to be treated from the main conveyance system;

b. a high flow bypass must be part of the inlet design; and

c. a flocculant storage/settling area must be incorporated into the design, and adequate maintenance access must be provided (minimum of 8 feet wide) for the removal of accumulated sediment. [Minn. R. 7090]

23.5

A designated person must perform visual monitoring of the treatment system for proper performance at least once every seven (7) days, and within 24 hours after a rainfall event greater than 2.5 inches in 24 hours. Following visual monitoring which occurs within 24 hours after a rainfall event, the next visual monitoring must be conducted within seven (7) days after that rainfall event. [Minn. R. 7090]

23.6

Three (3) benchmark monitoring stations must be established. Table 1 in Appendix A must be used for the parameters, units of measure, and frequency of measurement for each station. [Minn. R. 7090]

23.7

Samples must be collected as grab samples or flow-weighted 24-hour composite samples. [Minn. R. 7090]

23.8

Each sample, excluding pH samples, must be analyzed by a laboratory certified by the Minnesota Department of Health and/or the Agency, and:

a. sample preservation and test procedures for the analysis of pollutants must conform to 40 CFR Part 136 and Minn. R. 7041.3200;

b. detection limits for dissolved phosphorus, dissolved aluminum, and dissolved iron must be a minimum of 6 micrograms per liter, 10 micrograms per liter, and 20 micrograms per liter, respectively; and

c. pH must be measured within 15 minutes of sample collection using calibrated and maintained equipment. [Minn. R. 7090]

23.9

In the following situations, the permittee must perform corrective action(s) and immediately notify the Minnesota Department of Public Safety Duty Officer at 1-800-422-0798 (toll free) or 651-649-5451 (Metro area):

a. the pH of the discharged water is not within the range of 6.0 and 9.0;

b. any indications of toxicity or measurements exceeding water quality standards which could endanger human health, public drinking water supplies, or the environment; or

c. a spill or discharge or alteration resulting in water pollution as defined in Minn. Stat. 115.01, subd. 13, of alum or ferric chloride. If item b is applicable, the permittee must also report the non-compliance to the Commissioner as required in item 26.11.[Minn. R. 7001.0150, Subp. 3(L), Minn. R. 7090]

23.10

If the permittee discovers indications of toxicity or measurements exceeding water quality standards that the permittee determines does not endanger human health, public drinking water supplies, or the environment, the permittee must report the non-compliance to the Commissioner as required in item 26.12. [Minn. R. 7001.0150, Subp. 3(L), Minn. R. 7090]

23.11

The permittee must submit the following information with the annual report. The annual report must include a month-bymonth summary of:

a. date(s) of operation;

b. chemical(s) used for treatment;

c. gallons of water treated;

d. gallons of alum or ferric chloride treatment used;

e. calculated pounds of phosphorus removed; and

f. any performance issues and the corrective action(s), including the date(s) when corrective action(s) were taken. [Minn. R. 7090]

23.12

A record of the design parameters in items 23.13 through 23.15 must be kept on-site. [Minn. R. 7090]

23.13

Site-specific jar testing conducted using typical and representative water samples in accordance with the most current approved version of ASTM D2035. [Minn. R. 7090]]

23.14

Baseline concentrations of the following parameters in the influent and receiving waters:

a. aluminum or iron; and

b. phosphorus. [Minn. R. 7090]

23.15

The following system parameters and how each was determined:

a. flocculant settling velocity;

b. minimum required retention time;

c. rate of diversion of stormwater into the system;

d. the flow rate from the discharge of the outlet structure; and

e. range of expected dosing rates. [Minn. R. 7090]

23.16

The following site-specific procedures must be developed and a copy kept on-site:

a. procedures for the installation, operation and maintenance of all pumps, generators, control systems, and other equipment;

b. specific parameters for determining when the solids must be removed from the system and how the solids will be handled and disposed of; and

c. procedures for cleaning up and/or containing a spill of each chemical stored on-site. [Minn. R. 7090]