6. IRRIGATION and WETTABLE ACRES

6.1 Wettable Acres in a CAWMP

Wettable acres requirements apply to all facilities with irrigation systems. Systems using honey wagons and solid spreaders exclusively will not be affected. Acres which are wetted by an irrigation system with a 50% to 70% of wetted diameter sprinkler spacing or 60% to 90% of wetted diameter traveler lane spacing are considered wettable acres and can be counted in the WUP.

Wettable acres for spray fields with irrigation systems having excessive spacing, single pulls or a single row of stationary sprinklers, are limited to that portion of the spray field receiving a more uniform coverage. Wettable acres calculations are based on a width of 90% of wetted diameter for travelers or a single row of stationary sprinklers and 78% of wetted diameter for excessively spaced stationary sprinklers. Any overlap areas must only be counted once.

Wettable acres determination will be required on operations with a) more than 75% of the farm's total acres (on a per field basis) credited in the CAWMP as acres receiving waste and b) operations where this determination cannot be made due to lack of documentation, and c) a farm has a history of overapplication due to lack of sprayfield acres and/or the fields have obvious limitations past the 75% rule (i.e. ditches and/or odd shaped areas not irrigatable etc.) will be flagged for evaluation.

Operations will be flagged for evaluation on the inspection form through the Operation Review and Compliance Inspection processes, or through the permit application process.

After an operation is flagged, DWQ will notify the producer by certified mail requiring a wettable acre determination with the needed corrective action to be completed within six months. In order to balance the workload, no more than approximately 100 notifications will be sent by DWQ per month.

Operations will not be flagged for evaluation if they have one of the following components included in the CAWMP:

• An irrigation design and field map depicting wettable acres signed by an I or PE.
• D1 and D2 irrigation operating parameter sheets including field maps depicting wettable acres signed by an I or PE.
• D1 irrigation operating parameter sheet including field maps depicting wettable acres signed by a WUP Specialist.

Any producer that cannot meet the 6-month due date may request an administrative agreement with a compliance schedule from DWQ. Facilities that fail to provide adequate justification will be subject to appropriate enforcement actions.

Any facility that may have difficulty meeting the wettable acres criteria should identify a solution as soon as possible. Upon request by the producer/owner, DWQ will work closely with facilities with hardship cases to reach an amicable solution for DWQ and the producer/owner.

It is advisable for the producer/owner to assess wettable acres prior to application for a permit.

Wettable acres will be documented on the Wettable Acre Determination Field Data & Computation Worksheets that apply to the irrigation system (see NCCES Publications (Irrigated Acreage Determination Procedures for Wastewater Application Equipment, Stationary Sprinklers AG-553-6, Hard Hose Trader AG-553-7.)), completed and signed by the producer and a technical specialist (WUP/WA, I/WA, or P.E. designation). This form, including a wetted acres map becomes part of the waste management plan on file at the SWCD office and farm. Technical Specialists with I or WUP designation attending a full training session on wettable acres may receive WA designation.

If an operation has been pended due to lack of documentation to support a Wettable Acre Determination, DWQ will notify the producer by certified mail requiring them to supply the necessary information to the Compliance Inspector or Operation Reviewer who initially pended the facility. This information is to be completed within three months of receiving the certified letter. If the Inspector or Reviewer does not receive information within three months, the producer has only three additional months to complete the full Wettable Acre Determination and submit the Wettable Acre Determination Certification (Appendix 6.1) to the address listed on the form.

When a pended facility submits their information, the inspector or reviewer will log in the date received in the compliance database. Once the information is reviewed the inspector or reviewer will send a letter letting the producer know the current status. In the event this facility fails to provide adequate information to be exempt from a Wettable Acre Determination the facility will be sent a second letter when the facility has been selected.

Any facility that has been flagged can submit information to the inspector or reviewer who flagged the facility for review in order to be exempt. This is allowed only if the flagged facility has not received a formal letter starting the six month clock on their wettable acre determination.

All facilities that have been flagged for a wettable acre determination and have submitted the certification form will be reviewed by the inspector or reviewer at their next inspection by the flagging agency that initiated the flag.

6.2 Irrigation Record Keeping Methods

If a producer is keeping adequate records by field, he or she shall be allowed to continue using this record keeping system without penalty. Producers shall be encouraged to keep records by pull or zone. During the annual inspection or operation review, the inspector or reviewer has the responsibility to determine if record keeping is adequate. If the inspector/reviewer determines that a producer is keeping records inadequately by field, he or she must document in the report why the record keeping was inadequate, and then may require the producer to keep irrigation records either by pull/zone and/or to correct existing records. Acreage and irrigation records shall match acreage and irrigation records of CAWMP.

6.3 Maximum Irrigation Amount

The maximum irrigation-loading rate per irrigation event shall be based on a site evaluation. A maximum of no more than one-inch per irrigation event is allowed unless there is evidence, through soil moisture measurements, that the soil is capable of absorbing more effluent in the root zone, and provided no runoff occurs.

6.4 Irrigation Design Criteria

A design crediting effective irrigated acres must be used for installing irrigation equipment. The design must meet the recommendation of NCCES, which agrees with the irrigation uniformity coefficient in NRCS Irrigation Standard 442. NCCES recommends a range of 60 to 78% of wetted diameter for lane spacing for travelers and 50 to 65% of wetted diameter for stationary sprinklers NCCES publication (AG-553-6) Stationary Sprinkler Irrigation Systems columns D, E, and G in Table 1 through 4 provide acceptable sprinkler area allowances for effective wetted acres. NCCES publication (AG-553-7), Hard Hose Traveler Irrigation System, tables NE60 through N75+ provides acceptable area allowances for the traveler end areas.

Effective irrigated acres design requirements shall be met for 1) irrigation equipment installed on a new sprayfield after February 1, 1999, 2) new irrigation system on an existing sprayfield after February 1, 1999, and 3) underground hydrant lines after February 1, 1999. In an existing system, replacing equipment with similar items does not require meeting effective design requirements. For existing sprayfields, wettable acre criteria can be used to determine WUP acres even though effective design requirements shall be met. When an existing irrigation system is replaced, the new system shall be certified. The new system must meet buffer and setback requirements at the time the original system was installed.

Setback requirements are dependent upon the date the sprayfield is put into use. Therefore, plan revisions do not require setback changes unless a new sprayfield is added or expanded as described in Section 8.1.

6.5 Irrigation Design Checklist

A comprehensive checklist has been compiled to assist technical specialists with irrigation system design (Appendix 6.5).