HomeMy WebLinkAboutBLD2021-00208 - 05 STORMWATERSTORMWATER CALCULATIONS-IMPERVIOUS SURFACE
Impervious surface is a hard surface that either prevents or slows the entry of water into the soil as under natural conditions prior to development. A hard surface area which causes water to run off the surface in greater quantities or at an increased rate of flow from the flow present under natural conditions prior to development. Common impervious surfaces include, but are not limited to roof tops, walkways, patios, driveways, parking lots or storage areas, concrete or asphalt paving, gravel roads, packed earthen materials, and oiled, macadam or other surfaces which similarly impede the natural infiltration of stormwater.
NEW
Structures (all roof area)
Sidewalks
Patios
Solid Decks (without infiltration below)
_ __..(qll<.Z2..�(pe.-_sq/ft
_....;,..f'J....:....P\____;.__ __ sq1tt _N_f\� __ sq1tt __ 1\f�'1---__ sq1tt
EXISTING
Structures (all roof area)
Sidewalks
Patios
Solid Decks (without infiltration below)
_ft...._..-=28� __ sej/ft
_ _..,l'\ ...... [LLA_.__ ___ sq/ft
�2,�i_8 ___ sq/ft
�:2-�'2-i_':t�_sqttt
Driveway, parking, roads, etc _'""Nf\---'-...,__ ___ sq/ft Driveway, parking, roads, etc 1,.,J Ho sq/ft
_______ sq/ft Other -Pc:>12-q\ ___ P4 _____ sq/ft other
Total New _ ____._.x::. ...... s= ........... o.,c___s.q/ft Total Existing __ '7.....,,{ao::....::S',�(p"'------'sq/ft
TOTAL NEW+ TOTAL EXISTING* _....,� ..... $'<=-0.-..__ __ sq/ft "This amount will be used to check total lot coverage.
Divide the total existing
impervious surface above by the
size of the parcel and convert to
DEVELOPMENT v.REDEVELOPMENT
+ Does the site have > 35% or more
existina imoervious surface?
a percentage. 3, } 2 % The proposal is considered new development. Answer questions in Figure 2.4.1 Flow Chart for New
Development to determine project size (next page). The proposal is considered redevelopment Answer questions in Figure 2.4.2. Flow Chart for
Redevelopment to determine project size (next page).
~ Applicants for "small" projects must comply only with Minimum Requirement #2-Construction Stormwater Pollution Prevention. Please submit the Small Project Certification (Worksheet "s). The proponent is responsible for employing the 12 Elements to control erosion and prevent sediment and other pollutants from leaving the site during the construction phase of the project. Pick up the
Construction Stormwater Pollution Prevention (SWPPP) Best Management Practices (BMPs) Fact Sheet.
~ Applicants for "medium" projects-those that must meet only Minimum Requirements #1 through #5 must submit Worksheet Al and Bl, a stormwater site plan and a construction stormwater pollution prevention site plan (See Reference AlA and BlA for guidance).).
~ "Large" projects-those that must meet all 9 Minimum Requirements-must submit Worksheet Al and Bl, a stormwater site plan and a construction stormwater pollution prevention site plan (See Reference AlA and BlA for guidance). Large projects also may require engineering. See Worksheet L to determine additional large project requirements.
APPLICANT SIGNATURE By signing the Stormwater Calculation Worksheet, I as the applicant/owner attest that the information provided hereinis true and correct to the best of my knowledge. I also certify that this application is being made with the full knowledge and consent of all owners of n affected property.
(DATEi
stormwater celc worksheet QR code -REV. 5131/2019 page 2 of2
8,506 (A.H, 05/06/2021)