This page provides a general interpretation of existing methods for designing spray irrigation facilities, and also considers the relative effectiveness and limitations of these facilities.
Groundwater Discharges Section
Nitrogen Removal by Delaware Crops (University of Delaware)
Nutrient Content of Crops (USDA)
Nitrogen Management for Soybeans (University of Delaware)
Many of the topics listed below are referenced back to or provided as interpretation of requirements found in Delaware’s Regulations Governing the Design, Installation and Operation of On-Site Wastewater Treatment and Disposal Systems (7 DE Admin. Code, 7101).
The information provided below applies to Class C designers, Class D.3 soil scientists, Class E.4 system contractors, and spray irrigation professionals for the siting, designing, installing, and operating requirements of spray irrigation facilities.
Compliance Monitoring Report, Nitrogen Balance, and Operations and Maintenance Manual
BOD, TSS, pH Exceedances
Daily Permissible Average
Lysimeters (pan and suction)
Crop Nutrient Removal vs Crop Nutrient Uptake
Crop nutrient removal is lower than crop nutrient uptake because a significant percentage of the nutrients taken up by the crop are returned to the soil in the form of crop residues.
2.5 inches/week spray vs. monthly average
Precipitation – P5 vs. Average Values
Crop Growth/Uptake Curves/Standard Design for Crop Removal
See Crop Reference (EXCEL)
Below is a sample of what to expect in a permit, possibly located in Part I in a new section entitled “Design Criteria.”
During the period beginning on the effective date and lasting through the expiration date of this permit, the Permittee is authorized to discharge to the spray irrigation field(s) identified on page 1, in Part I.A, and depicted on page X of this permit the quantity and quality of effluent specified below and in accordance with the design documents listed in Part I.B of this permit:
1. The design loading rate proposed is a maximum of XXX,XXX GPD in accordance with the XXXX Design Engineer Report (see Design Loading Rate chart below). If facility operations face emergency or extenuating circumstances that would require the weekly quantity of effluent discharged to exceed 2.5 inches per acre per 7-day period, and the system would be able to assimilate both the hydraulic loading without exceeding the soils percolation capacity and the additional nitrogen loading without exceeding the limitations set forth in item 11 below, please contact the Groundwater Discharge Section for written authorization in accordance with Section 184.108.40.206.13.8.1 of the Regulations.
|Design Loading Rate per XXXX DER (inches/week) and (gallons/week)|