6400 MERRILL CREEK PKY 2018-01-01 MF Import

For infiltration basins, City standards require soil textural analyses to be performed on soil samples taken from \I the site in the area of the infiltration basin. Soil � samples should be taken at the location of the infiltration facility at two depths - the elevation of the bottom of the proposed system and 3 feet below the bottom of the proposed system. However, if the soil on the site appears uniform to the soil investigator, only one sample needs to be analyzed. \/ The design infiltration rate is determined using the chart `�" on paqe 4-13 of the City's standards and the results of the soil textural analyses. �oil/water separation and qrit removal is required upstream of the infiltration basin per the standards found in section 4-11. �he following information is required for City review and � pproval of infiltration basins: 1) soil log results 2) depth to high water mark, bedrock or hardpan, and/or impermeable soil layer 3) textural class of representative soil samples 4) the design infiltration rate 5) stage-storage relationship of basin 6) results of routing the design storm through the facility � 7) sizing calculations for the oil/water separation � and grit removal system i EJ �;�c� Oil/water seoaration and arit removal vault: �t'�t�� 1��"��trarCity standards call for these vaults to have a minimum �, c�" �(^ design flow determined by using the rational formula with a �� rainfall intensity of 0.5 inches per hour over the ��°.��,�^ ' _ �) contributing area. The vault is required to provide a 15 � ��; minute detention time for the design flow. (�' , 1� a City standards require flows larger than the 3esign flow to r �`� �r, • be bypassed around the vault. The crown of the vault inlet P„ti"�" should be at or below the invert elevation of the bypass pipe. The vault inlet pipe should be sized to convey the design flow under the head present when the invert of the overflcw pipe is reached. The flow through the vault should not exceed the maximum process flow (the largest flow the separator can handle before accumulated oil begins to be flushed out) when the head needed to pass the 25 year storm is reached in the highflow bypass pipe.