Chapter 21.75 STORMWATER PLAN

Chapter 21.75
STORMWATER PLAN

Sections:

21.75.010 Stormwater plan – When required.

21.75.020 Standards for stormwater plan.

21.75.010 Stormwater plan – When required.

a. This chapter applies to a stormwater plan (SWP) when required by another provision of the zoning code.

b. When a SWP is required, no person shall do or cause to be done any site development activity without first obtaining a SWP approved by the City.

c. A SWP shall be prepared and stamped by a person who is registered as a professional civil engineer in the State of Alaska. The engineer who prepares a SWP also shall submit to the Department written post-construction documentation that the installed mitigation methods meet the standards in HCC 21.75.020 and the requirements of the approved SWP. [Ord. 10-26 § 1, 2010; Ord. 08-29, 2008].

21.75.020 Standards for stormwater plan.

The SWP shall provide for the control of stormwater discharges, the control of total suspended solids, and the control of other pollutants carried in runoff. The SWP shall address and satisfy each of the standards established in this section.

a. Site designs shall minimize the channelization of stormwater (surface water runoff) that results from all natural forms of precipitation (including snow melt) and maximize pervious areas for stormwater absorption.

b. Stormwater runoff generated by development activities and discharged directly into wetlands, watercourses or waters of Kachemak Bay shall be adequately treated to limit nonpoint source and point source pollution.

c. Water quality management shall be provided through the use of structural and nonstructural practices.

d. Structural methods used for new development shall be designed to remove 80 percent of the average annual post-development total suspended solids load (TSS).

e. All stormwater from paved areas 25,000 square feet or larger subject to motor vehicle traffic shall flow through a spill-containment type of oil/water separator prior to discharge to eliminate nonpoint source pollution.

f. Development sites that include fixed storage in excess of 1,500 gallons of petroleum products shall utilize secondary containment or appropriately sized oil/water type centrifugal separators and shall incorporate a spill response plan within the SWP.

g. Development sites that transfer petroleum products shall utilize appropriately sized and located oil/water type centrifugal separators and shall incorporate a spill response plan within the SWP.

h. Source Control of Pollution. Pollution source control approved methods shall be applied to all projects to the maximum extent to eliminate any discharge.

i. The post-development stormwater discharge rate shall not exceed the pre-development peak discharge rate (PDR) for the 10-year frequency storm event, consisting of rainfall for a period of three consecutive hours at a rate of one-half inch per hour.

j. To protect stream channels from degradation, channel protection storage volume shall be provided based on two-year, three-hour duration storm.

k. Fuel and chemical residue or other types of potentially harmful material, such as animal waste, garbage or batteries, located in an area susceptible to runoff, shall be removed and disposed of according to applicable law.

1. All approved stormwater control methods shall be installed and maintained to ensure the system functions as designed, for the life of the development.

m. A schedule of monitoring and maintenance practices necessary to maintain the SWP control methods will be supplied by the developer to the City.

n. A record of ongoing monitoring and maintenance shall be maintained on the premises and shall be made available for inspection by the City. [Ord. 10-26 § 2, 2010; Ord. 08-29, 2008].

21.75.030 Financial responsibility.

a. A SWP submitted to the Department shall be accompanied by the following:

1. An estimate prepared by a person who is registered as a professional civil engineer in the State of Alaska of the cost of constructing and installing the mitigation methods and structures that are required to comply with the SWP; and

2. If the estimated cost exceeds $7,500, a performance guaranty meeting the requirements of subsection (b) of this section.

b. A performance guaranty shall be in the form of either a surety bond from a company authorized to do such business in the State, or a cash deposit with the City. The terms of the performance guaranty shall provide that if the developer defaults in constructing and installing the mitigation methods and structures that are required to comply with the SWP, the City may draw upon the performance guaranty to cure the default, but that such a drawing does not relieve the developer of its obligation to comply with the SWP. The amount of the performance guaranty shall be equal to 150 percent of the engineer’s estimate of the cost of constructing and installing the mitigation methods and structures that are required to comply with the SWP.

c. When the engineer who prepared a SWP submits to the Department written post-construction documentation that the installed mitigation methods and structures meet the standards in HCC 21.75.020 and the requirements of the approved SWP, the City shall release the performance guaranty for the SWP. [Ord. 10-26 § 3, 2010].