Frequently Asked Questions

The Stormwater Utility fee was enacted by Ordinance Title 12-02 effective July 1, 2003. Many of the questions that we have received are summarized on this page for your reference. If you have other questions or concerns that you would like to address, please contact us. Complete phone number and other means for contacting our section are shown on the Contact Us page of this website.

Utility Fee:

When did the Stormwater Utility fee go in to effect?

By Ordinance, SECTION 12-02-002-0001, the Stormwater Utility fee became effective July 1, 2003. The stormwater fee is billed as part of the City of Flagstaff utility bill.

What is an ERU?

ERU stands for Equivalent Run-off Unit. It is calculated by the number of square feet of impervious surface on your property. This is then divided by 1500 square feet to come up with an ERU. 1500 square feet was determined to be the most equitable basis of distribution.

What is an impervious surface?

Impervious surface is defined as those areas within developed land, which prevent or significantly impede the natural infiltration of stormwater into the soil. Common impervious surfaces include buildings, rooftops, asphalt streets, driveways, sidewalks, patios, decks, parking areas, brick or concrete pavers and compacted gravel surfaces.

How is the amount of impervious area calculated?

The impervious area of properties is determined by using aerial photographs and information in the City's Geographic Information Systems (GIS), along with parcel lines from the County Assessors Office.

How can I determine how much my stormwater utility fee will cost each month?

Effective June 1, 2009, the average Flagstaff residential property will pay $3.66 per month for stormwater fees. This is based on a billable area of between 3,001 and 4,500 square feet of impervious surface. We use a tiered billing system as displayed below:

Tiered Equivalent Runoff Units (ERU's)

Sq. Ft. of Impervious Area	# of ERU's	Monthly Fee
200 - 1500	1	$1.22
1501 - 3000	2	$2.44
3001 - 4500	3	$3.66
4501 - 6000	4	$4.88
6001 - 7500	5	$6.10

There is a maximum of 5 ERU's on single-family residential property. There is no maximum ERU cap on commercial or multi-family property. Commercial and multi-family properties continue in the above pattern with no maximum monthly charge.

The run-off on my property goes directly into the ground and does not affect the City stormwater system, why should I have to pay?

The stormwater fee and the impervious area calculation are a mechanism for equitably distributing the cost of the stormwater system maintenance and the need to comply with the federal mandate among all of the residents of Flagstaff who, in some way, use and contribute to the stormwater system and stormwater run-off.

Is it possible to receive a utility fee credit for certain measures and how can I apply?

Yes it is possible to receive a credit to the stormwater utility fee. The typical residential credit is approximately 10% of the monthly stormwater utility fee. For more details on how to qualify and how to apply please see the Stormwater Credit Manual which is available on the downloads page of this website.

How are the stormwater funds used?

Money collected from the Stormwater Fees is dedicated only to stormwater and cannot be used for anything else. The appropriate distribution of funds includes complying with Federal water quality regulations, maintenance of channels, structures, pipes and other elements of the storm drainage system.

What does the Stormwater staff do?

Regulatory compliance including: EPA requirements, ADEQ requirements, Title 12 of City Code, Stormwater Utility, Illicit Discharges, Community Rating System Classification. Stormwater Master Plan including: community assessment, infrastructure inventory, flood zone determinations. Construction inspection and site plan review including: rough & final grading inspections, SWPPP inspections. Drainage Improvement (DrIP) including: site specific drainage problem resolution. In addition to performing the required Floodplain Regulations, we are glad to assist with Flood Zone determinations.

Landscaping, Grading, and Roof Runoff:

How can I be sure that water will drain away from all sides of my house?

Lots should be graded so as to drain surface water away from foundation walls. The grade away from the foundation wall should slope away at a 5:1 slope, or fall 6 inches within the first 10 feet, except where lot lines or walls, slopes or other physical barriers prohibit, drains or swales shall be provided to ensure drainage away from foundation walls. Any landscaping done after purchase of the house must not interfere with the drainage pattern established by the original lot-grading plan.

Do I need to over-excavate before bringing in fill or landscaping material?

Generally yes! The area to be filled or covered should be excavated to the depth or thickness of the proposed fill material if it would change drainage conditions. The excavated material can be hauled off or used for mound building (landscaping) in other parts of the yard as long as:

• the mound doesn't cause water to drain directly onto the house;
• the mound doesn't prevent water from draining away from the house; and
• the total storage capacity of any depressed storage area is maintained.

How Can I be sure that roof runoff flows safely away from my house?

Roofs can generate an enormous amount of runoff. When the runoff is trapped in flat areas up against a wall, footing or stem wall of the house, where runoff cannot flow away from the house, ponding or flooding of an entryway can occur. In some cases water will percolate straight down along the wall, eventually causing settling and cracking of the slab or foundation. Possible solutions include grading, re-landscaping, enlarging wall openings, and/or removing obstructions to flow. All of these are designed to allow water to flow away from the house as quickly as it is running off the roof. Installing rain gutters on key sections of the roof, to collect and convey runoff to a safe location, is another possible solution, and in some cases may be the only practical solution. Do not allow gutter downspouts to empty onto flat ground next to a wall or footing. Add an extension to it so it can positively flow away from the house, if on a steep easily erodible slope you may need to provide a rock lined splash pad and channel to safely convey the water away from the house.

Walls and Fences

If I want to install a block wall or fence, are there any places I should avoid?

Block walls and fences can create some of the most serious flooding problems. If at all possible, avoid constructing walls across any channel or wash. Walls or fences should not extend beyond the designated building envelope of your lot or encroach into any drainage easement.

What types of things should I avoid if I have a wash on my property?

Avoid crossing washes with walls or fences. Stop walls at the edge of the drainage easement or the channel's floodplain and leave the wash area as common open space. Avoid crossing washes with your primary access or the only driveway to your house. Avoid diverting natural washes from their natural flow path. The City's Floodplain and Stormwater Ordinance requires that runoff should enter and depart from property in substantially the same manner as under pre-development conditions. If, for some reason, you must divert flow within your lot you must not alter a watercourse without City approval and certification from a professional engineer that any alterations will not increase flood levels or hazards within, upstream or downstream from the altered portion of the watercourse. Avoid building channels with bends sharper than a 45 degree turn.

If a wash is on my property, what should I do?

For an individual property owner, maintenance responsibilities on a wash running through your property consist mainly of keeping it clean. This means free of trash, debris and sediment; clear of overgrown, choking or clogging vegetation; free of obstructions or structures. The purpose is to maintain the free flow of water and not impede or reduce the water carrying capacity of the wash or channel. Washes must not be filled in, plugged, blocked, diverted or altered in any way.
In general: check and clean channels, grates and inlets in and around your property just before and during each rainy season (May and October) and during snow melt periods (all winter long).

Master Plan

I understand that the City is developing a Stormwater Master Plan. Where can I get more information on that? How can I provide input to that study?

Tom Hieb is managing Phase II of the city-wide Master Drainage Plan that will address major flooding problems and the need for large-scale drainage infrastructure improvements. For more information on the master plan please contact Tom Hieb by returning to the Contact Us page of this site.