7 Del. Admin. Code § 7103-64.0

Current through Register Vol. 28, No. 3, September 1, 2024

Section 7103-64.0 - Table 302-1 Hydraulic Conductivity Test Methods

64.1 Saturated Vertical Hydraulic Conductivity^a

64.1.1 Laboratory Tests^b:

Constant Head Method	ASTM D 2434-68
(coarse grained soils)	AASTHOT 215-70
Bowles (1978), pp 97-104
Kezdi (1980), pp 96-102
Falling Head Method	Bowles (1978),pp 105-110
(cohesive soils)	Kezdi (1980), pp 102-108

64.1.2 Field Tests:

Cylinder Infiltrometer	Boersma (1965)
U.S. EPA (1981),pp 3-17 to 19
Double Tube Method	Bower (1966)
U.S. EPA (1981), pp 3-24 to 3-27
Air-Entry Permeameter	Bower (1966)
Method	Reed and Crites (1984), pp 176-180 Topp and Binns (1976) U.S. EPA (1981), pp 3-24 to 3-27

64.2 Saturated Horizontal Hyraulic Conductivity^d S

64.2.1 Field Tests:

Auger Hole Methodc	Reed and Crites (1984), pp 165 to 168
U.S. EPA (1984), pp 3-31 to 35
Slug Test	Bouwer and Rice (1976)

64.3 ^aOther methods, properly documented, may be accepted by the Department. However, "standard" percolation tests as performed for septic tank drain fields are not acceptable. Basin flooding tests are appropriate only to design of rapid infiltration systems.

64.4 ^bThese tests require undisturbed" field samples properly prepared to insure saturation. Reconstructed field samples are not acceptable. A description of the field sampling technique should accompany the laboratory testing results.

64.5 ^cMethods recommended by the Department.

64.6 ^dTesting for saturated horizontal hydraulic conductivity is required at land treatment sites where drainage improvements are planned and where lateral, as opposed to vertical subsurface drainage, is the predominant drainage pathway.

64.7 Preapplication Treatment Requirements

64.7.1 General

64.7.1.1 Wastewater irrigation systems have a demonstrated ability to treat high strength organic wastes to low levels. However, such systems require management with particular attention paid to organic loading rates and aeration of the soil profile between wastewater applications.

64.7.1.1.1 The Department requires that all wastewaters containing domestic wastes receive biological treatment prior to irrigation. This is necessary to:

64.7.1.1.2 Protect the health of persons contacting the irrigated wastewater, and

64.7.1.1.3 Reduce the potential for odors in storage and irrigation.

64.7.1.1.4 Most industrial wastes will require some pretreatment but some may be suitable for direct land treatment by irrigation. The Department will evaluate such systems on a case-by-case basis. All industrial system Design Development Reports must contain copies of work place chemical lists. This information will aid the Department and the applicant in evaluating potential problems with a land treatment system. The principal criteria to be considered by the Department to not require pretreatment will be a demonstration that odors and nuisance conditions and adverse impacts to groundwater or soil such as clogging and runoff, will not occur.

64.7.2 Wastewater Reclamation Standards for domestic and municipal wastewater for BOD, TSS, and Disinfection, Based on Site Access Control.

64.7.2.1 The primary water quality objective for any reclaimed wastewater spray irrigation project is to prevent the spread of waterborne diseases while also preventing environmental degradation of the site and surrounding areas. Protection of public health can be achieved either by limiting public access to the site or by reducing the concentration of pathogenic bacteria and enteric viruses in the reclaimed wastewater. In cases where public access cannot be restricted, such as landscaped areas, golf courses, parks, and roadway medians, levels of wastewater pretreatment need to be increased in order to assure comparable public health safeguards exist. Epidemiological studies performed at domestic wastewater spray irrigation reclamation sites have shown that reclaimed wastewater treated to advanced levels with reduction of entritic viruses below detectable levels pose no ascertainable risks to public health. Based on these findings, the Department has established the following pretreatment requirements based on the level of site access control to be provided.

64.7.2.1.1 Restricted Public Access Sites (See subsection 73.2)

64.7.2.1.1.1 Restricted public access sites are sites where access to the site by the public is controlled and only accessible to authorized operators and farm personnel. All wastewater must be treated to a 5-day biochemical oxygen demand of 50 mg/L at average design flow and 75 mg/L under peak loads. Total suspended solids are limited to 50 mg/L for mechanical systems and 90 mg/L for ponds. Disinfection is required to yield a discharge not to exceed 200 colonies/100 mL fecal coliform at all times. Disinfection requirements may be waived when wastewater is irrigated in remote or restricted use sites such as forests.

64.7.2.2 Limited Public Access Sites

64.7.2.2.1 Limited public access sites are landscaped areas where public access is limited to specific periods of time and buffer zones pursuant to subsection 311 can be maintained to property boundaries and surface waters. Spray irrigation activities shall be limited to those periods of time when the public is effectively excluded from accessing the site. All wastewater irrigated on limited access sites must not exceed a 5-day biochemical oxygen demand of 30 mg/L. Total suspended solids are limited to 30 mg/L. Disinfection to reduce fecal coliform bacteria to 200 colonies/100 mL is required.

64.7.2.3 Unlimited Public Access Sites

64.7.2.3.1 Unlimited public access sites are those landscaped areas such as golf courses, residential lawns, cemeteries, parks, and highway medians which may not have adequate buffer zones and which are accessible to the public at all times. An example is the typical residential golf course community where private homes abut the fairways and greens, and the public cannot effectively be excluded from accessing the site during spray irrigation.All wastewaters used for irrigation of unlimited access sites must be pretreated to advanced limits with high- level disinfection. The advanced treatment system shall include the following processes: oxidation,clarification, coagulation, flocculation, filtration, and disinfection.The wastewater shall not contain more than ten (10(c) mg/L total suspended solids, and turbidity shall not exceed five (5(c) TU. 5-day biochemical oxygen demand shall not exceed ten (10(c) mg/L, and the wastewater must be disinfected to reduce fecal coliforms to a level below 20 colonies/100 mL.

64.7.3 Nitrogen

64.7.3.1 Maximum nitrogen removal occurs when nitrogen is land applied in the ammonia or organic form. Nitrate is not retained by the soil and leaches to the groundwater, especially during periods of dormant plant growth. Therefore, the preapplication treatment system should not produce a nitrified effluent.

64.7.3.2 The Department recommends that aerated or facultative wastewater stabilization ponds be used for preapplication treatment where possible. These systems generally produce a low-nitrate effluent well suited for wastewater irrigation. When mechanical plants are employed for preapplication treatment, they should be designed and operated to limit nitrification.

64.7.3.3 The Design Development Report shall indicate the expected range of nitrogen removal in the preapplication treatment system. Predictive equations for nitrogen removal in facultative wastewater stabilization ponds have been developed by Pano and Middlebrooks (1982), and Reed (1985).

64.7.4 Pretreatment Systems and Storage Ponds

64.7.4.1 Pretreatment may consist of mechanical or pond-type systems. All systems must have provisions for storage either as a separate facility or incorporated into the pretreatment system if the efficiency of treatment is not compromised. Pretreatment ponds may be aerated, facultative or a combined aerated/facultative system. The storage pond and the irrigation pump station must be designed such that pumping does not affect the design hydraulic detention time. The Department recommends the United States Environmental Protection Agency's October 1983 Design Manual: Municipal Wastewater Stabilization Ponds as a reference for design of preapplication treatment ponds.

64.7.4.2 Ponds used for preapplication treatment and storage must have impermeable liners. Facultative pond cells should have an appropriate length to width ratio consistent with current practice to minimize short circuiting with a depth between 3 and 5 feet. Sizing of completely and partially mixed aerated ponds should be based on first-order removal rate kinetic equations and the expected annual temperature variation. Adequate freeboard is required for all ponds to contain excess rainfall and wastewater flows.

64.7.4.3 Treatment facilities for wastewater to be used on unlimited access sites shall include continuous on-line monitoring for turbidity before application of the disinfectant. Continuous on-line monitoring of residual disinfection concentrations, shall be provided at the compliance monitoring point for limited and unlimited access sites. The permittee shall develop and submit for the Department's review and approval, an operating protocol designed to insure that the high-level disinfection criteria will be met before the wastewater is released to the storage impoundment system or to the wastewater reuse system. Automatic diversion of wastewater that fails to meet the operating criteria shall be established in the operating protocol. Such diversions shall be to a reject wastewater storage system. Increased reject wastewater storage capacity shall be provided if needed.

64.7.4.4 Reclaimed wastewater that fails to meet the criteria established in the operating protocol shall not be discharged into the storage impoundment system or to the reuse system. Such substandard wastewater (reject wastewater) shall be either stored in a separate off-line system for subsequent additional treatment, or shall be discharged to another permitted reuse system requiring lower levels of pretreatment, or to a permitted effluent disposal system.

7 Del. Admin. Code § 7103-64.0