# septic.str Data contained in the septic.str data file are: type of septic system, geometry of biozone, characteristics of biomass, and bio-physical reaction coefficients occurring in the biozone (adapted from Siegrist et al. (2005)). | Field | Description | Type | Unit | Default | Range | | ------------------------------------------------------------------------------------------------------------------------------------------- | ---------------------------------------------------------------------------------------------------------- | ------- | ------------ | ------- | -------- | | [name](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/name_sepdb) | Name of septic system record | string | n/a | n/a | n/a | | [typ](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/typ) | Septic system type | integer | n/a | 0 | | | [yr](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/yr) | ​Year the septic system became operational | integer | n/a | 0 | | | [operation](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/operation) | ​Septic system operation flag | integer | n/a | 0 | 0-2 | | [residents](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/residents) | ​Number of permanent residents in the house | real | n/a | 1 | 1.0-12.0 | | [area](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/area) | ​Average area of drainfield of individual septic systems | real | m^2 | 1 | | | [t\_fail](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/t_fail) | Time until failing systems gets fixed | integer | days | 0 | 0-150 | | [dp\_bioz](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/dp_bioz) | Depth to the top of the biozone layer from the ground surface | real | mm | 1 | | | [thk\_bioz](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/thk_bioz) | Thickness of biozone layer | real | mm | 1 | | | [cha\_dist](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/cha_dist) | Distance from septic system to the stream | real | km | 2 | | | [sep\_dens](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/sep_dens) | Number of septic systems per square kilometer | real | n/a | 2 | | | [bm\_dens](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/bm_dens) | Density of biomass | real | kg/m^3 | 1 | | | [bod\_decay](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/bod_decay) | BOD decay rate coefficient | real | m^3/day | 2 | | | [bod\_conv](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/bod_conv) | Conversion factor representing the proportion of mass bacterial growth and mass BOD degraded in the septic | real | n/a | 2 | | | [fc\_lin](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/fc_lin) | Linear coefficient for calculation of field capacity in the biozone | real | n/a | 1 | | | [fc\_exp](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/fc_exp) | Exponential coefficient for calculation of field capacity in the biozone | real | n/a | 2 | | | [fecal\_delay](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/fecal_decay) | Fecal coliform bacteria decay rate coefficient | real | m^3/day | 2 | | | [tds\_conv](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/tds_conv) | Conversion factor for plaque from TDS | real | n/a | 2 | | | [mort](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/mort) | Mortality rate coefficient | real | n/a | 2 | | | [resp](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/resp) | Respiration rate coefficient | real | n/a | 3 | | | [slough1](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/slough1) | Linear coefficient for calculating the rate of biomass sloughing | real | n/a | 2 | | | [slough2](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/slough2) | Exponential coefficient for calculating the rate of biomass sloughing | real | n/a | 2 | | | [nit](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/nit) | Nitrification rate coefficient | real | n/a | 2 | | | [denit](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/denit) | Denitrification rate coefficient | real | n/a | 3 | | | [p\_sorp](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/p_sorp) | Linear P sorption distribution coefficient | real | L/kg | 1 | | | [p\_sorp\_max](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/p_sorp_max) | Maximum P sorption capacity | real | mg P/kg soil | 1 | | | [solp\_slp](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/solp_slp) | Slope of the linear effluent soluble P equation | real | n/a | 3 | | | [solp\_int](https://swatplus.gitbook.io/io-docs/~/changes/GiVD5ID0WVyRIAumaMy2/introduction/structural-practices/septic.str/solp_init) | Intercept of the linear effluent soluble P equation | real | n/a | 3 | | #### References > Siegrist, R.L., J. McCray, L. Weintraub, C. Chen, J. Bagdol, P. Lemonds, S. Van Cuyk, K. Lowe, R. Goldstein, and J. Rada (2005): Quantifying Site-Scale Processes and Watershed-Scale Cumulative Effects of Decentralized Wastewater Systems. Project No. WU-HT-00-27. Prepared for the National Decentralized Water Resources Capacity Development Project, Washington University, St. Louis, MO, by the Colorado School of Mines.