13-109

Other

• Improvement factor for channel protection (>1 acreacre43,560 square feet — about the size of an American football field without the end zones.)0.8

  I.F (Improvement Factor) equals 0.8 for sites > 1 acre or 0.9 for sites ≤ 1 acre.

• Improvement factor for channel protection (≤1 acreacre43,560 square feet — about the size of an American football field without the end zones.)0.9

  I.F (Improvement Factor) equals 0.8 for sites > 1 acre or 0.9 for sites ≤ 1 acre.

• Downstream limit of analysis distance150 ft

  A point that is at least 150 feet downstream of a point where the receiving pipe or channel is joined by another that has a drainage area that is at least 90 percent of the size of the first drainage area at the point of confluence; or A point that is at least 150 feet downstream of a point where the drainage area is 360 acres or greater.

• Drainage area threshold for downstream analysis360 acresacre43,560 square feet — about the size of an American football field without the end zones.

  A point that is at least 150 feet downstream of a point where the drainage area is 360 acres or greater.

• Flood protection design storm10 year

  Concentrated stormwater flow shall be released into a stormwater conveyance system and shall meet one of the following criteria as demonstrated by the use of acceptable hydrologic and hydraulic methodologies: ... ten-year 24-hour storm event.

• Stormwater facility inspection frequency5 years

  The owner shall provide the city with access to the facility to perform quality assurance inspections and follow up inspections to ensure adequate maintenance has been conducted a minimum of once every five years, or on a more frequent basis at the discretion of the director.

• Stormwater BMP maintenance agreement required

  The owner shall enter into a stormwater BMP maintenance agreement (agreement) with the city that provides all necessary provisions to ensure compliance with this article, to include access for inspections.

• Total phosphorus load reduction for prior developed lands (>=1 acreacre43,560 square feet — about the size of an American football field without the end zones.)20 pct

  For land-disturbing activities disturbing greater than or equal to one acre that results in no net increase in impervious cover from the pre-development condition, the total phosphorus load shall be reduced at least 20 percent below the pre-development total phosphorus load.

• Total phosphorus load reduction for prior developed lands (<1 acreacre43,560 square feet — about the size of an American football field without the end zones.)10 pct

  For regulated land-disturbing activities disturbing less than one acre that results in no net increase in impervious cover from the pre-development condition, the total phosphorus load shall be reduced at least ten percent below the predevelopment total phosphorus load.

• Land disturbance threshold for stormwater quality requirements2,500 sqftsq ftSquare feet. An acre is 43,560 sq ft; a typical suburban lot is 7,000–10,000.

  All development, redevelopment, and uses disturbing greater than 2,500 square feet shall meet the following storm water quality management performance requirements.

• Vegetated buffer width for intermittent streams and non-tidal wetlands50 ft

  A 50-foot wide vegetated area preserved where present, or established where not present, on the outward edge of these features shall be considered a sufficient BMP to meet this standard if the vegetated area is designed to prevent erosion and scouring.

• Entire water quality volume treatment

  The entire water quality volume from the site shall be treated.