Precipitation (Official Record). NOAA Multi-Radar Multi-Sensor (MRMS) gauge-corrected quantitative precipitation estimates, point-extracted at the site coordinates (30.094937, -95.93169) from the
Iowa Environmental Mesonet reanalysis (Iowa State University). Values are calendar-day totals and finalize the morning after observation.
Inspection trigger (cumulative 24-hour). An inspection is required when 0.5 inch or more of rain accumulates within any rolling 24-hour period, including multiple smaller storms that together reach 0.5 inch (TXR150000 Part III.F.8(c)). The rolling-24-hour total is computed from NCEP Stage IV hourly gauge-corrected QPE via IEM; Stage IV values are provisional for roughly a day and finalize over the following several days.
Calculation Formula. Estimated runoff volume per event in gallons = rainfall (inches) x site area (217,800 sq ft = 5.00 acres) x runoff coefficient 0.80 (post-construction, per the SWPPP) x 0.623 (gallons in one inch of rain over one square foot). This is about 108,550 gallons per inch of rain over the site, and is an estimate.
Field Observations. Inspections and dewatering observations are entered and maintained by authorized personnel under the SWPPP's inspection authority.
Regulatory Basis. Inspection frequency (14-day routine; within 24 hours of a 0.5 in rain event) and record retention follow
TPDES Construction General Permit TXR150000 Part III. SWPPP prepared by
K4 Environmental.