Forms and Publications

Exhibit 33 Excel Calculators

Download Exhibit 33 Storm Water Detention Excel Spreadsheet Calculators

Save these Excel Spreadsheet Calculators to your hard drive.

Combined Exhibit 33 Storm Water Detention Calculator  
Exhibit 33 to calculate the results of all three calculators below. Enter site data on the first page only and a summary of all results will be displayed on the first page, the individual calculators seen below will be automatically populated on the subsequent sheets of the workbook.

Exhibit 33 Storm Water Detention Q1 - Q10 Calculator  
Exhibit 33 to calculate the intermediate volume and the lower Pre Development Q1 orifice release rate.

Exhibit 33 Storm Water Detention Q10 - Q100 Calculator  
Exhibit 33 to calculate the required total volume, the Pre Development Q10 orifice release rate and the Post Development Q100 release rate.

Exhibit 33 Storm Water Detention Exemption Calculator  
Exhibit 33 to calculate Storm Water Detention Exemption only.


The material published herein by Hamilton County Planning + Development as a public service and is believed to be accurate and current. Hamilton County Planning + Development shall not be held liable for damages of any kind regarding the use of the information as there are no warranties or guarantees of any kind concerning the material.

The calculators are free for individuals to use via this site. These calculators are intended solely for general information and educational purposes, and are provided to help decrease the learning curve for those inexperienced in the engineering field and to give more experienced users additional reference tools.

These engineering calculators are in no way a replacement for a thorough engineering review or design. A Professional Engineer, licensed in the appropriate field of engineering, should always conduct a formal evaluation under the circumstances. Any calculations performed by these engineering calculators are based on data and assumptions provided by you, and any risks associated with such data and assumptions shall be borne by you.

These engineering calculators are provided "as is". Hamilton County Planning + Development has introduced the information in the publication in good faith, however, they are not responsible for or liable for errors, misinformation, misprints or typographical errors. Hamilton County Planning + Development make no claims of the accuracy of the information contained herein.

No material in this publication may be reproduced in whole or in part without the written consent of Hamilton County Planning + Development.

Water Quality Design Resources

All development and redevelopment in the unincorporated townships of Hamilton County that disturb over 1 acre are subject to compliance with Hamilton County Storm Water District's Article V - Post Construction Storm Water Quality Regulations and Ohio EPA's Construction General Permit (OHC000005).

OEPA's Storm Water Technical Assistance materials provide a multitude of resources to aid in the design of Post Construction Stormwater Controls. Typically, a development will be required to detain the calculated Water Quality Volume for the minimum drain time required for the chosen Post-Construction Practice as specified in Table 510-C of Article V.

Lastly, Ohio's Rainwater and Land Development Manual (RLDM) provides design standards, specifications, and guidelines for designing pre-approved Post Construction Stormwater Controls as well as design criteria for required forebays, micropools, and acceptable pretreatment options. This Manual also provides design specifications for alternative BMPs, pre- through post-construction runoff and erosion control, and Runoff Reduction Practices.

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