The resource documents linked in the article above are long, and a PDF of each is available at the Tehama County Public Works website. For the convenience and reference of visitors to mineralcalifornia.com, key excerpts from the project report and the master plan are reproduced here, with webmaster-added emphasis indicated by italicization and webmaster commentary or modifications indicated with brackets.

Important: page numbers refer to the “jump to” function on the PDF itself, rather than the table of contents.

EXCERPTS: Wastewater Collection and Treatment Improvement Project

[Section II] J. Evaluation of Excessive I&I to the System [PDF pp. 30-35; photos not reproduced]

Based on review of the 2015 to 2017 WWTP flow records, the three-year ADWF is approximately 0.037 MGD. A current population of 310 results in an average daily flow of just under 120 gallons per capita per day. As such, a Sewer System Evaluation Survey is not required. However, further investigation was completed as part of the 2019 WWMP further described below.

A review of historical wet weather flows at the WWTP indicated an instantaneous PWWF of 0.713 MGD was recorded on March 22, 2018. This day also resulted in a four-hour sustained peak of 0.70 MGD and average daily PWWF of 0.57 MGD. Thus, during wet weather conditions, the current peaking factor is about 15. This is much higher than is typically acceptable and is a significant component of the system flow.

Given the current population of 310, this equates to a wet weather flow of just over 1,838 gallons per capita per day. Average wet weather flow (AWWF) in recent years is 0.12 MGD, or about 380 gallons per capita per day. It is important to note, inaccuracy of the influent flow measurements was recently discovered in the summer of 2019. Therefore, the peak flows utilized herein should be re-evaluated when the next significant winter occurs to verify accuracy of historic peak measurements.

A review of WWTP records (ADWF of 0.037 MGD and PWWF of 0.57 MGD) suggests that, at PWWF, an extremely large portion (94%) of the wastewater flows are due to I&I, and it is believed most of this may be from infiltration. This is based on the observation that it takes a prolonged period of rain to significantly increase I&I flows at the WWTP. Furthermore, plant flows appear to drop off relatively slowly following a period of intense rainfall.

[History of NPS HQ Contributions to I&I]

Since 1982, numerous I&I studies have been performed in the District as well as a few projects to fix deficiencies identified during those I&I monitoring efforts. It has been known for many years the Park Service has been a large contributor of system I&I. Instantaneous flow measurements completed in April and May of 1982 indicated the Park Service contributed an average of 47% of the total WWTP flow in three monitoring events. One additional measurement completed on January 24, 1983, indicated the Park Service contributed about 24% of the total WWTP flow. Six additional instantaneous flow measurements were taken between January 8, 1986, and March 10, 1989, all following wet weather events. The average flow contribution from the Park Service to the WWTP during these measurements was 42%.

As part of the 2019 WWMP, an I&I flow monitoring unit was installed in the Park Service manhole from January 18 through March 5, 2018. A summary of the I&I data gathered during this time indicated the Park Service manhole contributed approximately 18.5% of the total I&I to the WWTP. However, from the I&I monitoring effort, the ADWF measured from the Park Service was 10,728 gallons per day (GPD), or about 73 HEs. This is more than twice of what the Park Service is currently billed for, which is 4,810 GPD, or about 33 HEs. As such, the difference of 40 HEs in ADWF was attributed to I&I, increasing the Park Service I&I contribution to 21% of the total I&I flow entering the WWTP. While this contribution is far less than it has been in past measurements, it is still a significant portion that should be reduced.

Photo 13 – I&I Flow Monitor [Photo not reproduced]

Numerous other measurements of the Park Service flow contribution were taken in 2018 and 2019, the result of which are shown in Table 5. As shown therein, only one additional monitoring event was completed when flow monitors were installed in both the 6-inch Park Service pipeline and the 8-inch upstream pipeline. From May 10 through May 27, 2019, the flow monitors indicated the Park Service was still contributing 46% of the total influent flow compared to 54% from the rest of the system. The remaining measurements and flows included in Table 5 were calculated from depths measured by the District in each of the respective pipelines.

[Timing of CCTV Inspections, NPS Infrastructure Replacement Project, and Wastewater Treatment Plant Flow Meter Replacement and Circular Chart Update]

It should be noted that construction at the Park Service was ongoing during most of this data collection. Complete water and sewer system replacement was finished by late summer 2019, which should significantly reduce the contribution historically observed there. Additionally, it was also discovered early in the summer of 2019 that the aging inefficient flow meter was reading on average about 40% too high of what actual influent flows were. As such, a new influent flow meter was installed in June 2019 and recalibrated on August 13, 2019, which now accurately reflects true influent flows. The circular chart recorder was also updated at this time with a new continuous paperless recorder. It has been initially set up to record influent flows every ten minutes, which will allow for much greater accuracy in determining peaks, averages, and totals compared to a 7-day chart recorder. Smaller flow recording increments should be particularly helpful in better identifying the intermittent peak flow contribution from the USFS Campground and Church Camp.

To locate problem areas and obvious sources of I&I in collection system mains, the District most recently completed closed-circuit television (CCTV) inspection of the entire collection system from August to October 2017. Inspection was performed in accordance with the National Association of Sewer Service Companies (NASSCO) Pipeline Assessment and Certification Program (PACP) and Manhole Assessment and Certification Program (MACP) standards and procedures. Per NASSCO standards, each pipeline inspected received a condition grade ranging from 1 to 5, with 5 being the most significant defect and 1 being a minor defect. Grades were assigned based on the significance of the defect, extent of damage, percentage of restriction to flow capacity, or amount of wall loss due to deterioration. Each pipe segment received a separate segment grade score for both structural and O&M defects depending on the condition grade number and the number of occurrences in the segment.

Photo 14 – I&I from Park Service during ADWF [Photo not reproduced]

[2017 Sewer Main CCTV Inspection Results]

Of the nearly 19,800 feet of pipeline inspected, CCTV results showed only the pipelines included in Table 6 [PDF p. 65] to have defects of some kind that require attention. Results of the CCTV inspection identified ten locations in which there were mechanical deficiencies in the existing pipelines including holes, significant root intrusion, offset joints, broken lateral connections, pipe deformities, etc. There were also several pipelines identified with multiple significant defects including many offset joints, root intrusion, and infiltration resulting in recommendation of replacing the entire pipeline segment. The rating score should be viewed with caution since a high overall score may indicate a high number of low-severity defects, a low number of high-severity defects, or a balance of high- and low-severity defect grades. Of the 87 manholes inspected, only the five manholes included in Table 7 [PDF p. 66] were determined to have defects that require attention.

Photo 15 – CCTV Showing Root Intrusion [Photo not reproduced]

[Conclusions from CCTV Lateral Inspections & Troubleshooting History]

CCTV inspection of the mains revealed a relatively tight system with just over 1,100 feet of pipeline recommended for replacement. As such, it was suspected the source of I&I could be from laterals and private house connections. The District Board of Directors passed Ordinance No. 15 on May 22, 2001. Refer to Appendix C. Per this ordinance, the District owns and maintains the lateral from the main line to the property line, and the property owner must maintain the building sewer from the property line into the building. The 1989 PER for the Meadowview Area Sewer Project indicated that smoke testing and subsequent leak testing of sewer laterals were completed in the early to mid-1980s. At that time, letters were mailed to property owners with problems identified on private property, and all noted problems were reportedly corrected. However, this effort was completed more than 30 years ago. Additional smoke testing completed in September 2010 only identified a handful of deficiencies that were all reportedly remedied. It is suspected that elevated groundwater in the area may minimize the efficiency of smoke testing by preventing detection of defects.

In another attempt to determine if laterals are contributing to system infiltration, CCTV of as many laterals as possible was completed from July through September 2019. Lateral CCTV revealed more than 71% of the initial 89 laterals inspected have deficiencies that require additional attention, whether that be complete replacement, repair, or cleaning and subsequent CCTV. This ranged from large collapses and significant roots to cleanouts below grade or sags. Most deficiencies identified were minor roots, offset joints, or sags rather than large holes or significant roots at every joint. However, this was the case in some laterals, and even minor deficiencies contribute to system I&I. Many cleanouts were found to be deficient and in some cases below grade. It is recommended these be raised above grade or placed in an enclosed utility box and adequately capped as applicable. Refer to Table 8 for lateral CCTV results and associated recommendations [PDF p. 67].

Note that only 45% of service connections were inspected. Remaining laterals either could not be located, do not have a cleanout to allow for CCTV of the lateral, or had not yet been investigated at the time of this report. It is recommended cleanouts be installed at all houses and property lines, if they are not already, and either leakage testing be completed to verify flows are within maximum allowances or CCTV be completed after cleanout installation to determine if the lateral has deficiencies. Letters should be sent to property owners requiring repair or replacement of those building sewers with noted deficiencies. The District has already started this process. [Letters were sent June 10, 2019]

Improvements recommended herein do not currently include replacement of identified deficient private laterals or installation of cleanouts and subsequent CCTV inspection, as it is expected these will be paid for by individual homeowners. The District will need to be diligent in following up with letters sent and implementing fines as needed to ensure improvements are made.

[Section III] G. Additional Facilities or Actions Needed to Comply with WDRs [PDF p. 41]

No additional facilities or actions are needed to meet current WDRs. However, to correct current WWTP and collection system operational deficiencies, several improvements are immediately recommended including the following:

•Repair of ten pipeline mechanical deficiencies identified via CCTV to repair broken pipe, eliminate roots, offset joints, etc.

•Replacement of four manholes identified via CCTV.

•Replacement of approximately 1,100 feet of existing deficient 6-inch pipe to be replaced with new 6-inch PVC pipe, 955 feet of which consists of existing AC pipe and 150 feet of existing deficient PVC pipe.

•Installation of a UPS and remote monitoring capabilities at the WWTP.

•Installation of steps with railing at Percolation and Evaporation Ponds 1 and 2.

•Replacement of Filter Supply Pumps.

•Replacement of the auto dialer, bladder tank, and alarm system.

•Installation of manual transfer switch and j-box.

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EXCERPT: Wastewater Master Plan [PDF pp. viii-ix]

Wastewater Collection System

The existing Mineral wastewater collection system currently consists of about 14,600 feet of 6-inch, 5,400 feet of 8-inch, and 100 feet of 10-inch collector sewer mains. The entire collection system consists of gravity pipelines, with no lift stations required to convey influent wastewater to the WWTP. Portions of the District wastewater collection system are more than 65 years old and consist of asbestos cement pipe. The District has an extremely high peak wet weather flow (PWWF) to average dry weather flow (ADWF) ratio of 15.4 as measured during the highest inflow event. However, it is important to note it was discovered in the summer that the influent flow meter was reading on average about 40% too high of what actual influent flows were. Future monitoring will need to verify accuracy of historic flows, which are the basis of many components of this 2019 WWMP. Historically high infiltration and inflow (I&I) indicates deficient sewers in need of replacement. However, closed circuit television (CCTV) inspection of all collection system mains completed in 2017 revealed a relatively tight system. Only about 1,300 feet of pipeline was recommended for replacement, and 10 locations were found to have a mechanical deficiency of some kind including holes, offset joints, pipe deformities, etc. Given that the majority of collection system mains are not in bad condition, CCTV of about 45% of system laterals was completed from July through September 2019.

Wastewater Treatment Plant

The Mineral WWTP has an existing design ADWF capacity of approximately 0.07 million gallons per day (MGD) and a PWWF capacity of 0.75 MGD. The July through September, 2015 through 2017, ADWF was estimated to be about 0.037 MGD, or 52% of the current permitted ADWF capacity. PWWF at the WWTP was recorded at 0.57 MGD on March 22, 2018, or 81% of the peak design capacity. Existing WWTP capacity is more than adequate to meet projected 20-year PWWF, assuming an annual growth rate of 0.3%. WWTP improvements recommended herein are due to existing defects and deficiencies rather than to accommodate growth.