5 Colo. Code Regs. § 1002-73.4

Current through Register Vol. 47, No. 20, October 25, 2024

Section 5 CCR 1002-73.4 - DETERMINATIONS OF WASTELOAD

For municipal, domestic and industrial discharges, the monthly and annual wasteloads shall be determined as follows:

1. Direct Discharge.

For each direct discharge, monthly phosphorus loads (pounds) contributed shall be determined based upon the following formula:

Monthly Phosphorus Load (pounds) = Monthly volume discharged (million gallons) X Average Phosphorus Concentration (mg/l) for that month X 8.34.

The monthly volume (million gallons) = the sum of all total volumes of effluent measured at each permitted wastewater outfall ÷ number of measurements.

Average Phosphorus Concentration (mg/l) = the sum of the total phosphorus concentrations (mg/l) of all samples for the month ÷ the number of samples collected during the month.

2. Land Application.

a. Land Treatment. For each land treatment discharge, monthly phosphorus load (pounds) contributed shall be determined based upon the following formulas:

i. Monthly Phosphorus Load

Monthly Phosphorus Load (pounds) = sum of the Phosphorus Masses (pounds) for the month X Land Application Return Factor.

Monthly Phosphorus Load (pounds) = sum of loads from each land treatment site (monthly Phosphorus Mass at each land treatment site X Area Ratio for the land treatment site X Land Application Return Factor for the land treatment site)

ii. Phosphorus Mass

Phosphorus Mass = 8.34 X concentration value (mg/l) for phosphorus determined for the sample X the volume of water applied to the land (gallons) ÷ 1,000,000

iii. Phosphorus Concentration

Phosphorus concentrations for land treatment sites may be monitored either (1) at the land treatment site below the surface and above the seasonal high groundwater level, or (2) in the system prior to land application.

b. Land Disposal. For each land disposal discharge, monthly phosphorus load (pounds) contributed shall be determined based upon the following formulas:

i. Monthly Phosphorus Load

Monthly Phosphorus Load (pounds) = Monthly volume discharged (million gallons) X Average Phosphorus Concentration (mg/l) for that month X 8.34 X Land Application Return Factor.

ii. Monthly Volume

The monthly volume (million gallons) = the sum of all total volumes measured at or calculated for the month for all wastewater land applied.

iii. Average Phosphorus Concentration

Average Phosphorus Concentration (mg/l) = the sum of the total phosphorus concentrations (mg/l) of all samples for the month ÷ the number of samples collected during the month.

iv. Phosphorus Concentration Phosphorus concentrations for land disposal sites must be measured prior to land application.

c. Exemption. The Division may determine that a land application discharger has no phosphorus discharge, or a reduced phosphorus discharge, if the discharger demonstrates that:

(1) the discharger land applies, or will land apply, at agronomic rates for the specific vegetative species at the land application site, and

(2) the discharger has installed, or will install, soil moisture probes or other systems to assure land application at agronomic rates. Further, for such dischargers, the Division may authorize reduced monitoring requirements for discharge volume or phosphorus.

d. Site Approval. The Division shall use the return flow percent in a decreed augmentation plan to calculate phosphorus discharge loads for the site application of a land application discharger, if the discharger demonstrates that:

(1) the discharger land applies, or will land apply, at agronomic rates for the specific vegetative species at the land application site, and

(2) the discharger has installed, or will install, soil moisture probes or other systems to assure land application at agronomic rates.

3. Annual Phosphorus Wasteload.

The annual phosphorus wasteload shall be the sum of the 12 monthly phosphorus loads calculated for that calendar year for permitted wastewater discharge points and sites and shall not exceed the wasteload allocations, set forth in section 73.3.

5 CCR 1002-73.4

44 CR 14, July 25, 2021, effective 8/14/2021