6.3.2.b Water Quality Discussion

Variations due to human activity

Anthropogenic activities including septic tanks, agricultural activities, petroleum handling and distribution facilities, solid waste disposal sites, illegal and illicit discharges, dumping, industrial facilities, and other such activities can have a negative impact on groundwater and other sources of water.

It is important to identify the sources of these activities, quantify their effects, initiate remedial action where appropriate, and take steps to prevent future contamination. Pesticides, Total Dissolved Solids (TDS), Volatile Organic Carbons, and nitrates are the most common results of human related groundwater pollution in Surprise.

Most of the unincorporated Maricopa County area was developed without sanitary sewer lines and groundwater cumulatively has been affected by low density development relying on septic tanks and domestic wells. The continued absence of sanitary sewer lines in the unincorporated areas and the newly incorporated areas will result in shallow soil degradation due to higher wastewater volume flowing through on-site disposal systems.

Line extension to outlying areas is recommended to minimize domestic use of septic systems which have a negative impact on shallow groundwater quality. The preferred alternative is the extension of both water and sanitary sewer lines into the unincorporated area lying within the city’s planned service areas. Some groundwater quality problems are a consequence of leaking underground storage tanks which housed petroleum products or other hazardous materials. Currently there is no evidence as to the leaking of any underground storage tanks in the Surprise Planning Area.

Variations due to well depth

Groundwater in Surprise generally requires deep wells and the quality of water has required more extensive treatment than water from wells in the past due to more stringent regulatory requirements. The natural quality of deep or confined aquifers tends to be less variable, than shallow groundwater, the quality changes typically reflect the geochemical reactions that occur naturally as water migrates through confining layers of the aquifers from recharge areas including recharge from natural storm water runoff to the point of use of the well. In addition continued pumping of a confined aquifer can cause inflow of water from nearby unconfined areas that differs considerably in quality from water originally in the confined aquifer. The presence of arsenic, fluorides, radiochemicals, nitrates, and dissolved solids of the water are the result of variations in depth. Generally elevated levels of salinity have been reported in this part of Arizona. Arizona is among a handful of western states whose soil naturally contains levels of arsenic and fluoride that are slightly above the NPDWR’s standards but are not considered an unreasonable health risk.

Figure 6.3C

Regulatory Settings

In 1974, the United States Environmental Protection Agency (USEPA) established the Safe Drinking Water Act (SDWA) to protect public health by regulating the nation’s public drinking water. The law has been amended since then and requires stringent actions to protect drinking water and its sources. The SDWA has established enforceable standards for several contaminants. The NPDWRs are legally enforceable standards that apply to community and public water systems. These standards protect public health by limiting the level of following contaminants: microorganisms, disinfectants, disinfection byproducts, disinfectants, inorganic chemicals, organic chemicals, and radionuclides.

Meanwhile the Clean Water Act (CWA) is the cornerstone of surface water quality protection in the United States. The statute employs a variety of regulatory and non-regulatory tools to reduce discharge of pollutants into waterways, to finance municipal wastewater treatment facilities, and to manage polluted runoff. Based on CWA, the Phase II National Pollutant Discharge Elimination System (NPDES) rule, adopted by the EPA and administered by the Arizona Department of Environmental Quality (ADEQ), requires operators of small municipal separate storm sewer systems to obtain a NPDES permit and implement programs and activities to reduce pollutants in storm water runoff. The City of Surprise, as an operator of a municipal storm drain system prepared a Storm Water Management Plan and began implementation of this plan in 2003. In order to comply with the Phase II NPDES requirements, the plan acts as the city’s permit, describing actions that include best management practices, measurable goals, and timetables for implementation of six minimum control measures as follows:

• Public education and outreach.
• Public Participation/Involvement.
• Illicit discharge detention and elimination.
• Construction site storm water runoff control.
• Post construction storm water management.
• Pollution prevention for municipal operations.

The city also maintains Storm Drain Design and Construction Standards and Specifications. These include guidance for design and construction of manholes, detention/retention basins, sidewalk under-drains, and other items appurtenant to storm drainage systems.

Current city of Surprise standards for storm drainage are as follows:

• 10-year storm – Arterials and collectors shall carry the ten-year flow between the curbs, maintain a twelve foot dry lane in each direction and carry the 100-year flow within the right-of-way.
• 25-year storm – Ponding water in streets is not allowed.
• 100-year storm (FEMA BFE) – In general, development in or modification of the floodplain is discouraged. Development should be located outside the 100-year floodplain and development in the floodway is prohibited. Finished floor elevations of all buildings must be one foot above the 100-year water surface elevation. The 100-year, two hour storm event precipitation depth is a minimum of 2.8 inches for the city of Surprise.
• Designated areas – All finished floors shall be a minimum of 18 inches above the low outfall of the lot, i.e. low top of curb. All finished floor elevations of all buildings must be one foot above the 100-year, two hour water surface elevation.
• Detention of runoff in parking lots of industrial/commercial developments is allowed subject to the following standards:
  
  • No more than 75 per cent of the volume required maybe retained in the parking lot.
  • Depth in parking lots shall not exceed 0.67 feet.
  • A continuous emergency vehicle access lane, free of ponding water from the detention areas, shall be provided throughout the developments.
• All basins must drain within a 36 hour period.

The topography of the area also plays an important role in surface drainage. The city is mostly flat, with slopes generally from the northwest to the southeast. The ground surface elevation in the city varies from essentially from approximately 1,120 feet – 3,360 feet above sea level in the mountainous area within the Surprise Planning Area. The city’s surface water management system includes the washes, channels, conduits, culverts, and detention basins. Preservation and enhancement of the natural channels offers an excellent opportunity to improve the flood conveyance capacity and enhance habitat values. At present the city has a basic municipal storm drain system, the goal being to retain the storm water in the areas in which the storm water is collected hence recharging the aquifer in the area of use. Currently the minimum pipe size diameter for storm drain pipes is 18 inches..